\usepackage[T1]{fontenc,url}
\usepackage{lmodern} % using Latin Modern to be able to use bold typewriter font
\urlstyle{sf}
-\usepackage{babel,textcomp,csquotes,ifimasterforside,varioref,graphicx}
+\usepackage{listings}
+\usepackage{tabularx}
+\usepackage{tikz}
+\usepackage{tikz-qtree}
+\usetikzlibrary{shapes,snakes,trees,arrows,shadows,positioning,calc}
+\usepackage{babel,textcomp,csquotes,ifimasterforside,varioref}
\usepackage[hidelinks]{hyperref}
\usepackage{cleveref}
-\usepackage[style=numeric-comp,backend=bibtex]{biblatex}
+\usepackage[style=alphabetic,backend=bibtex]{biblatex}
\usepackage{amsthm}
-\usepackage{todonotes}
+\usepackage{graphicx}
+% use 'disable' before printing:
+\usepackage[]{todonotes}
\usepackage{xspace}
\usepackage{he-she}
\usepackage{verbatim}
\newcommand{\explanation}[3]{\noindent\textbf{\textit{#1}}\\*\emph{When:}
#2\\*\emph{How:} #3\\*[-7px]}
-\newcommand{\type}[1]{\texttt{\textbf{#1}}}
+%\newcommand{\type}[1]{\lstinline{#1}}
+\newcommand{\code}[1]{\texttt{\textbf{#1}}}
+\newcommand{\type}[1]{\code{#1}}
\newcommand{\typeref}[1]{\footnote{\type{#1}}}
\newcommand{\typewithref}[2]{\type{#2}\typeref{#1.#2}}
\newcommand{\method}[1]{\type{#1}}
\newcommand{\refactoring}[1]{\emph{#1}}
\newcommand{\ExtractMethod}{\refactoring{Extract Method}\xspace}
\newcommand{\MoveMethod}{\refactoring{Move Method}\xspace}
+\newcommand{\ExtractAndMoveMethod}{\refactoring{Extract and Move Method}\xspace}
\newcommand\todoin[2][]{\todo[inline, caption={2do}, #1]{
\begin{minipage}{\textwidth-4pt}#2\end{minipage}}}
\bibliography{bibliography/master-thesis-erlenkr-bibliography}
+ % UML comment in TikZ:
+ % ref: https://tex.stackexchange.com/questions/103688/folded-paper-shape-tikz
+\makeatletter
+\pgfdeclareshape{umlcomment}{
+ \inheritsavedanchors[from=rectangle] % this is nearly a rectangle
+ \inheritanchorborder[from=rectangle]
+ \inheritanchor[from=rectangle]{center}
+ \inheritanchor[from=rectangle]{north}
+ \inheritanchor[from=rectangle]{south}
+ \inheritanchor[from=rectangle]{west}
+ \inheritanchor[from=rectangle]{east}
+ % ... and possibly more
+ \backgroundpath{% this is new
+ % store lower right in xa/ya and upper right in xb/yb
+ \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
+ \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
+ % compute corner of ‘‘flipped page’’
+ \pgf@xc=\pgf@xb \advance\pgf@xc by-10pt % this should be a parameter
+ \pgf@yc=\pgf@yb \advance\pgf@yc by-10pt
+ % construct main path
+ \pgfpathmoveto{\pgfpoint{\pgf@xa}{\pgf@ya}}
+ \pgfpathlineto{\pgfpoint{\pgf@xa}{\pgf@yb}}
+ \pgfpathlineto{\pgfpoint{\pgf@xc}{\pgf@yb}}
+ \pgfpathlineto{\pgfpoint{\pgf@xb}{\pgf@yc}}
+ \pgfpathlineto{\pgfpoint{\pgf@xb}{\pgf@ya}}
+ \pgfpathclose
+ % add little corner
+ \pgfpathmoveto{\pgfpoint{\pgf@xc}{\pgf@yb}}
+ \pgfpathlineto{\pgfpoint{\pgf@xc}{\pgf@yc}}
+ \pgfpathlineto{\pgfpoint{\pgf@xb}{\pgf@yc}}
+ \pgfpathlineto{\pgfpoint{\pgf@xc}{\pgf@yc}}
+ }
+}
+\makeatother
+
+\tikzstyle{comment}=[%
+ draw,
+ drop shadow,
+ fill=white,
+ align=center,
+ shape=document,
+ minimum width=20mm,
+ minimum height=10mm,
+ shape=umlcomment,
+ inner sep=2ex,
+ font=\ttfamily,
+]
+
\begin{document}
\ififorside
\frontmatter{}
\chapter*{Abstract}
-\todoin{\textbf{Remove all todos (including list) before delivery/printing!!!}}
+\todoin{\textbf{Remove all todos (including list) before delivery/printing!!!
+Can be done by removing ``draft'' from documentclass.}}
\todoin{Write abstract}
\tableofcontents{}
a refactoring.
In the extreme case one could argue that such a thing as \emph{software
-obfuscation} is to refactor. If we where to define it as a refactoring, it could
-be defined as a composite refactoring \see{compositeRefactorings}, consisting
-of, for instance, a series of rename refactorings. (But it could of course be
-much more complex, and the mechanics of it would not exactly be carved in
-stone.) To perform some serious obfuscation one would also take advantage of
-techniques not found among established refactorings, such as removing
-whitespace. This might not even generate a different syntax tree for languages
-not sensitive to whitespace, placing it in the gray area of what kind of
-transformations is to be considered refactorings.
+obfuscation} is refactoring. Software obfuscation is to make source code harder
+to read and analyze, while preserving its semantics. It could be done composing
+many, more or less randomly chosen, refactorings. Then the question arise
+whether it can be called a \emph{composite refactoring}
+\see{compositeRefactorings} or not? The answer is not obvious. First, there is
+no way to describe \emph{the} mechanics of software obfuscation, beacause there
+are infinitely many ways to do that. Second, \emph{obfuscation} can be thought
+of as \emph{one operation}: Either the code is obfuscated, or it is not. Third,
+it makes no sense to call software obfuscation \emph{a} refactoring, since it
+holds different meaning to different people. The last point is important, since
+one of the motivations behind defining different refactorings is to build up a
+vocabulary for software professionals to reason and discuss about programs,
+similar to the motivation behind design patterns\citing{designPatterns}. So for
+describing \emph{software obfuscation}, it might be more appropriate to define
+what you do when performing it rather than precisely defining its mechanics in
+terms of other refactorings.
\section{The etymology of 'refactoring'}
It is a little difficult to pinpoint the exact origin of the word
also present in the Forth\footnote{\emph{Forth} -- stack-based, extensible
programming language, without type-checking. See \url{http://www.forth.org}}
community, and the word ``refactoring'' is mentioned in a book by Leo Brodie,
-called \emph{Thinking Forth}\citing{brodie1984}, first published in
+called \emph{Thinking Forth}\citing{brodie2004}, first published in
1984\footnote{\emph{Thinking Forth} was first published in 1984 by the
\emph{Forth Interest Group}. Then it was reprinted in 1994 with minor
typographical corrections, before it was transcribed into an electronic edition
typeset in \LaTeX\ and published under a Creative Commons licence in 2004. The
edition cited here is the 2004 edition, but the content should essentially be as
-in 1984.}. The exact word is only printed one place~\cite[p.~232]{brodie1984},
+in 1984.}. The exact word is only printed one place~\cite[p.~232]{brodie2004},
but the term \emph{factoring} is prominent in the book, that also contains a
whole chapter dedicated to (re)factoring, and how to keep the (Forth) code clean
and maintainable.
\begin{quote}
\ldots good factoring technique is perhaps the most important skill for a
- Forth programmer.~\cite[p.~172]{brodie1984}
+ Forth programmer.~\cite[p.~172]{brodie2004}
\end{quote}
\noindent Brodie also express what \emph{factoring} means to him:
Factoring means organizing code into useful fragments. To make a fragment
useful, you often must separate reusable parts from non-reusable parts. The
reusable parts become new definitions. The non-reusable parts become arguments
- or parameters to the definitions.~\cite[p.~172]{brodie1984}
+ or parameters to the definitions.~\cite[p.~172]{brodie2004}
\end{quote}
Fowler claims that the usage of the word \emph{refactoring} did not pass between
independently in each of the communities.
\section{Motivation -- Why people refactor}
-To get a grasp of what refactoring is all about, we can try to answer this
-question: \emph{Why do people refactor?} Possible answers could include: ``To
-remove duplication'' or ``to break up long methods''. Practitioners of the art
-of Design Patterns\citing{designPatterns} could say that they do it to introduce
-a long-needed pattern into their program's design. So it is safe to say that
-peoples' intentions are to make their programs \emph{better} in some sense. But
-what aspects of the programs are becoming improved?
+There are many reasons why people want to refactor their programs. They can for
+instance do it to remove duplication, break up long methods or to introduce
+design patterns\citing{designPatterns} into their software systems. The shared
+trait for all these are that peoples intentions are to make their programs
+\emph{better}, in some sense. But what aspects of their programs are becoming
+improved?
As already mentioned, people often refactor to get rid of duplication. Moving
identical or similar code into methods, and maybe pushing methods up or down in
Many software design pattern are aimed at lowering the coupling between
different classes and different layers of logic. One of the most famous is
-perhaps the \emph{Model-View-Controller}\citing{designPatterns} pattern, or
-\emph{MVC} for short. It is aimed at lowering the coupling between the user
-interface and the business logic and data representation of a program. This also
-has the added benefit that the business logic could much easier be the target of
-automated tests, increasing the productivity in the software development
-process. Refactoring is an important tool on the way to something greater.
+perhaps the \emph{Model-View-Controller}\citing{designPatterns} pattern. It is
+aimed at lowering the coupling between the user interface and the business logic
+and data representation of a program. This also has the added benefit that the
+business logic could much easier be the target of automated tests, increasing
+the productivity in the software development process. Refactoring is an
+important tool on the way to something greater.
Another effect of refactoring is that with the increased separation of concerns
coming out of many refactorings, the \emph{performance} can be improved. When
design. \See{relationToDesignPatterns}
\end{description}
-\section{Tool support}\label{toolSupport}
-
-\subsection{Tool support for Java}
+\section{Tool support (for Java)}\label{toolSupport}
This section will briefly compare the refatoring support of the three IDEs
\emph{Eclipse}\footnote{\url{http://www.eclipse.org/}}, \emph{IntelliJ
IDEA}\footnote{The IDE under comparison is the \emph{Community Edition},
present an example of an \ExtractMethod refactoring followed by a \MoveMethod
refactoring that breaks a program in both the \emph{Eclipse} and \emph{IntelliJ}
IDEs\footnote{The NetBeans IDE handles this particular situation without
- altering ther program's beavior, mainly because its Move Method refactoring
- implementation is a bit rancid in other ways \see{toolSupport}.}. The
+ altering the program's beavior, mainly because its Move Method refactoring
+ implementation is a bit flawed in other ways \see{toolSupport}.}. The
following piece of code shows the target for the composed refactoring:
\begin{minted}[linenos,samepage]{java}
tests. It does not generate compilation errors, and will thus only result in
a runtime error or corrupted data, which might be hard to detect.
-\section{Refactoring and testing}\label{testing}
+\section{Refactoring and the importance of testing}\label{testing}
\begin{quote}
If you want to refactor, the essential precondition is having solid
tests.\citing{refactoring}
\end{quote}
-When refactoring, there are roughly two kinds of errors that can be made. There
-are errors that make the code unable to compile, and there are the silent
-errors, only popping up at runtime. Compile-time errors are the nice ones. They
-flash up at the moment they are made (at least when using an IDE), and are
-usually easy to fix. The other kind of error is the dangerous one. It is the
-kind of error introduced in the example of \myref{correctness}. It is an error
-sneaking into your code without you noticing, maybe. For discovering those kind
-of errors when refactoring, it is essential to have good test coverage. It is
-not a way to \emph{prove} that the code is correct, but it is a way to make you
-confindent that it \emph{probably} works as desired. In the context of test
-driven development, the tests are even a way to define how the program is
-supposed to work. It is then, by definition, working if the tests are passing.
+When refactoring, there are roughly three classes of errors that can be made.
+The first class of errors are the ones that make the code unable to compile.
+These \emph{compile-time} errors are of the nicer kind. They flash up at the
+moment they are made (at least when using an IDE), and are usually easy to fix.
+The second class are the \emph{runtime} errors. Although they take a bit longer
+to surface, they usually manifest after some time in an illegal argument
+exception, null pointer exception or similar during the program execution.
+These kind of errors are a bit harder to handle, but at least they will show,
+eventually. Then there are the \emph{behavior-changing} errors. These errors are
+of the worst kind. They do not show up during compilation and they do not turn
+on a blinking red light during runtime either. The program can seem to work
+perfectly fine with them in play, but the business logic can be damaged in ways
+that will only show up over time.
+
+For discovering runtime errors and behavior changes when refactoring, it is
+essential to have good test coverage. Testing in this context means writing
+automated tests. Manual testing may have its uses, but when refactoring, it is
+automated unit testing that dominate. For discovering behavior changes it is
+especially important to have tests that cover potential problems, since these
+kind of errors does not reveal themselves.
+
+Unit testing is not a way to \emph{prove} that a program is correct, but it is a
+way to make you confindent that it \emph{probably} works as desired. In the
+context of test driven development (commonly known as TDD), the tests are even a
+way to define how the program is \emph{supposed} to work. It is then, by
+definition, working if the tests are passing.
If the test coverage for a code base is perfect, then it should, theoretically,
-be risk-free to perform refactorings on it. This is why tests and refactoring
-are such a great match.
+be risk-free to perform refactorings on it. This is why automated tests and
+refactoring are such a great match.
+
+\subsection{Testing the code from correctness section}
+The worst thing that can happen when refactoring is to introduce changes to the
+behavior of a program, as in the example on \myref{correctness}. This example
+may be trivial, but the essence is clear. The only problem with the example is
+that it is not clear how to create automated tests for it, without changing it
+in intrusive ways.
+
+Unit tests, as they are known from the different xUnit frameworks around, are
+only suitable to test the \emph{result} of isolated operations. They can not
+easily (if at all) observe the \emph{history} of a program.
+
+This problem is still open.
+
+\todoin{Write?}
+\begin{comment}
+
+Assuming a sequential (non-concurrent) program:
+
+\begin{minted}{java}
+tracematch (C c, X x) {
+ sym m before:
+ call(* X.m(C)) && args(c) && cflow(within(C));
+ sym n before:
+ call(* X.n()) && target(x) && cflow(within(C));
+ sym setCx after:
+ set(C.x) && target(c) && !cflow(m);
+
+ m n
+
+ { assert x == c.x; }
+}
+\end{minted}
+
+%\begin{minted}{java}
+%tracematch (X x1, X x2) {
+% sym m before:
+% call(* X.m(C)) && target(x1);
+% sym n before:
+% call(* X.n()) && target(x2);
+% sym setX after:
+% set(C.x) && !cflow(m) && !cflow(n);
+%
+% m n
+%
+% { assert x1 != x2; }
+%}
+%\end{minted}
+\end{comment}
+
+\section{The project}
+The aim of this master project will be to investigate the relationship between a
+composite refactoring composed of the \ExtractMethod and \MoveMethod
+refactorings, and its impact on one or more software metrics.
+
+The composition of the \ExtractMethod and \MoveMethod refactorings springs
+naturally out of the need to move procedures closer to the data they manipulate.
+This composed refactoring is not well described in the literature, but it is
+implemented in at least one tool called
+\emph{CodeRush}\footnote{\url{https://help.devexpress.com/\#CodeRush/CustomDocument3519}},
+that is an extension for \emph{MS Visual
+Studio}\footnote{\url{http://www.visualstudio.com/}}. In CodeRush it is called
+\emph{Extract Method to
+Type}\footnote{\url{https://help.devexpress.com/\#CodeRush/CustomDocument6710}},
+but I choose to call it \ExtractAndMoveMethod, since I feel it better
+communicates which primitive refactorings it is composed of.
+
+For the metrics, I will at least measure the \emph{Coupling between object
+classes} (CBO) metric that is described by Chidamber and Kemerer in their
+article \emph{A Metrics Suite for Object Oriented
+Design}\citing{metricsSuite1994}.
+
+The project will then consist in implementing the \ExtractAndMoveMethod
+refactoring, as well as executing it over a larger code base. Then the effect of
+the change must be measured by calculating the chosen software metrics both
+before and after the execution. To be able to execute the refactoring
+automatically I have to make it analyze code to determine the best selections to
+extract into new methods.
-\section{Software metrics}
-\todoin{Is this the appropriate place to have this section?}
%\part{The project}
%\chapter{Planning the project}
-\chapter{\ldots}
-\todoin{write}
+\chapter{The Project}
+
\section{The problem statement}
+\todoin{write/move}
+
\section{Choosing the target language}
-Choosing which programming language to use as the target for manipulation is not
-a very difficult task. The language has to be an object-oriented programming
-language, and it must have existing tool support for refactoring. The
-\emph{Java} programming language\footnote{\url{https://www.java.com/}} is the
-dominating language when it comes to examples in the literature of refactoring,
-and is thus a natural choice. Java is perhaps, currently the most influential
-programming language in the world, with its \emph{Java Virtual Machine} that
-runs on all of the most popular architectures and also supports\footnote{They
-compile to java bytecode.} dozens of other programming languages, with
-\emph{Scala}, \emph{Clojure} and \emph{Groovy} as the most prominent ones. Java
-is currently the language that every other programming language is compared
-against. It is also the primary language of the author of this thesis.
+Choosing which programming language the code that shall be manipulated shall be
+written in, is not a very difficult task. We choose to limit the possible
+languages to the object-oriented programming languages, since most of the
+terminology and literature regarding refactoring comes from the world of
+object-oriented programming. In addition, the language must have existing tool
+support for refactoring.
+
+The \emph{Java} programming language\footnote{\url{https://www.java.com/}} is
+the dominating language when it comes to example code in the literature of
+refactoring, and is thus a natural choice. Java is perhaps, currently the most
+influential programming language in the world, with its \emph{Java Virtual
+Machine} that runs on all of the most popular architectures and also supports
+dozens of other programming languages\footnote{They compile to java bytecode.},
+with \emph{Scala}, \emph{Clojure} and \emph{Groovy} as the most prominent ones.
+Java is currently the language that every other programming language is compared
+against. It is also the primary programming language for the author of this
+thesis.
\section{Choosing the tools}
When choosing a tool for manipulating Java, there are certain criterias that
popular\citing{javaReport2011} among them and seems to be de facto standard IDE
for Java development regardless of platform.
+\section{Organizing the project}
+All the parts of this master project is under version control with
+\emph{Git}\footnote{\url{http://git-scm.com/}}.
+
+The software written is organized as some Eclipse plugins. Writing a plugin is
+the natural way to utilize the API of Eclipse. This also makes it possible to
+provide a user interface to manually run operations on selections in program
+source code or whole projects/packages.
+
+When writing a plugin in Eclipse, one has access to resources such as the
+current workspace, the open editor and the current selection.
+
+\section{Continuous integration}
+The continuous integration server
+\emph{Jenkins}\footnote{\url{http://jenkins-ci.org/}} has been set up for the
+project\footnote{A work mostly done by the supervisor.}. It is used as a way to
+run tests and perform code coverage analysis.
+
+To be able to build the Eclipse plugins and run tests for them with Jenkins, the
+component assembly project
+\emph{Buckminster}\footnote{\url{http://www.eclipse.org/buckminster/}} is used,
+through its plugin for Jenkins. Buckminster provides for a way to specify the
+resources needed for building a project and where and how to find them.
+Buckminster also handles the setup of a target environment to run the tests in.
+All this is needed because the code to build depends on an Eclipse installation
+with various plugins.
+
+\subsection{Problems with AspectJ}
+The Buckminster build worked fine until introducing AspectJ into the project.
+When building projects using AspectJ, there are some additional steps that needs
+to be performed. First of all, the aspects themselves must be compiled. Then the
+aspects needs to be woven with the classes they affect. This demands a process
+that does multiple passes over the source code.
+
+When using AspectJ with Eclipse, the specialized compilation and the weaving can
+be handled by the \emph{AspectJ Development
+Tools}\footnote{\url{https://www.eclipse.org/ajdt/}}. This works all fine, but
+it complicates things when trying to build a project depending on Eclipse
+plugins outside of Eclipse. There is supposed to be a way to specify a compiler
+adapter for javac, together with the file extensions for the file types it shall
+operate. The AspectJ compiler adapter is called
+\typewithref{org.aspectj.tools.ant.taskdefs}{Ajc11CompilerAdapter}, and it works
+with files that has the extensions \code{*.java} and \code{*.aj}. I tried to
+setup this in the build properties file for the project containing the aspects,
+but to no avail. The project containing the aspects does not seem to be built at
+all, and the projects that depends on it complains that they cannot find certain
+classes.
+
+I then managed to write an \emph{Ant}\footnote{\url{https://ant.apache.org/}}
+build file that utilizes the AspectJ compiler adapter, for the
+\code{no.uio.ifi.refaktor} plugin. The problem was then that it could no longer
+take advantage of the environment set up by Buckminster. The solution to this
+particular problem was of a ``hacky'' nature. It involves exporting the plugin
+dependencies for the project to an Ant build file, and copy the exported path
+into the existing build script. But then the Ant script needs to know where the
+local Eclipse installation is located. This is no problem when building on a
+local machine, but to utilize the setup done by Buckminster is a problem still
+unsolved. To get the classpath for the build setup correctly, and here comes the
+most ``hacky'' part of the solution, the Ant script has a target for copying the
+classpath elements into a directory relative to the project directory and
+checking it into Git. When no \code{ECLIPSE\_HOME} property is set while running
+Ant, the script uses the copied plugins instead of the ones provided by the
+Eclipse installation when building the project. This obviously creates some
+problems with maintaining the list of dependencies in the Ant file, as well as
+remembering to copy the plugins every time the list of dependencies change.
+
+The Ant script described above is run by Jenkins before the Buckminster setup
+and build. When setup like this, the Buckminster build succeeds for the projects
+not using AspectJ, and the tests are run as normal. This is all good, but it
+feels a little scary, since the reason for Buckminster not working with AspectJ
+is still unknown.
+
+The problems with building with AspectJ on the Jenkins server lasted for a
+while, before they were solved. This is reflected in the ``Test Result Trend''
+and ``Code Coverage Trend'' reported by Jenkins.
+
\chapter{Refactorings in Eclipse JDT: Design, Shortcomings and Wishful
Thinking}\label{ch:jdt_refactorings}
\todo{What about the language specific part?}
\subsection{The Language Toolkit}
-The Language Toolkit, or LTK for short, is the framework that is used to
-implement refactorings in Eclipse. It is language independent and provides the
-abstractions of a refactoring and the change it generates, in the form of the
-classes \typewithref{org.eclipse.ltk.core.refactoring}{Refactoring} and
-\typewithref{org.eclipse.ltk.core.refactoring}{Change}. (There is also parts of
-the LTK that is concerned with user interaction, but they will not be discussed
-here, since they are of little value to us and our use of the framework.)
+The Language Toolkit\footnote{The content of this section is a mixture of
+ written material from
+ \url{https://www.eclipse.org/articles/Article-LTK/ltk.html} and
+ \url{http://www.eclipse.org/articles/article.php?file=Article-Unleashing-the-Power-of-Refactoring/index.html},
+the LTK source code and my own memory.}, or LTK for short, is the framework that
+is used to implement refactorings in Eclipse. It is language independent and
+provides the abstractions of a refactoring and the change it generates, in the
+form of the classes \typewithref{org.eclipse.ltk.core.refactoring}{Refactoring}
+and \typewithref{org.eclipse.ltk.core.refactoring}{Change}.
+
+There are also parts of the LTK that is concerned with user interaction, but
+they will not be discussed here, since they are of little value to us and our
+use of the framework. We are primarily interested in the parts that can be
+automated.
\subsubsection{The Refactoring Class}
The abstract class \type{Refactoring} is the core of the LTK framework. Every
refactoring\typeref{org.eclipse.ltk.core.refactoring.participants.ProcessorBasedRefactoring}.
It then delegates to its given
\typewithref{org.eclipse.ltk.core.refactoring.participants}{RefactoringProcessor}
-for condition checking and change creation.
+for condition checking and change creation. Participating in a refactoring can
+be useful in cases where the changes done to programming source code affects
+other related resources in the workspace. This can be names or paths in
+configuration files, or maybe one would like to perform additional logging of
+changes done in the workspace.
\subsubsection{The Change Class}
This class is the base class for objects that is responsible for performing the
\subsubsection{Missing Flexibility from JDT Refactorings}
The JDT refactorings are not made with composition of refactorings in mind. When
a JDT refactoring is executed, it assumes that all conditions for it to be
-applied successfully can be found by reading source files that has been
+applied successfully can be found by reading source files that have been
persisted to disk. They can only operate on the actual source material, and not
(in-memory) copies thereof. This constitutes a major disadvantage when trying to
-compose refactorings, since if an exception occur in the middle of a sequence of
-refactorings, it can leave the project in a state where the composite
-refactoring was executed only partly. It makes it hard to discard the changes
+compose refactorings, since if an exception occurs in the middle of a sequence
+of refactorings, it can leave the project in a state where the composite
+refactoring was only partially executed. It makes it hard to discard the changes
done without monitoring and consulting the undo manager, an approach that is not
bullet proof.
\See{hacking_undo_history}
\section{Wishful Thinking}
-
+\todoin{???}
\chapter{Composite Refactorings in Eclipse}
As pointed out in \myref{ch:jdt_refactorings}, the Eclipse JDT refactoring model
is not very well suited for making composite refactorings. Therefore a simple
model using changer objects (of type \type{RefaktorChanger}) is used as an
-abstraction layer on top of the existing Eclipse refactorings.
+abstraction layer on top of the existing Eclipse refactorings, instead of
+extending the \typewithref{org.eclipse.ltk.core.refactoring}{Refactoring} class.
+
+The use of an additional abstraction layer is a deliberate choice. It is due to
+the problem of creating a composite
+\typewithref{org.eclipse.ltk.core.refactoring}{Change} that can handle text
+changes that interfere with each other. Thus, a \type{RefaktorChanger} may, or
+may not, take advantage of one or more existing refactorings, but it is always
+intended to make a change to the workspace.
+
+\subsection{A typical \type{RefaktorChanger}}
+The typical refaktor changer class has two responsibilities, checking
+preconditions and executing the requested changes. This is not too different
+from the responsibilities of an LTK refactoring, with the distinction that a
+refaktor changer also executes the change, while an LTK refactoring is only
+responsible for creating the object that can later be used to do the job.
+
+Checking of preconditions is typically done by an
+\typewithref{no.uio.ifi.refaktor.analyze.analyzers}{Analyzer}. If the
+preconditions validate, the upcoming changes are executed by an
+\typewithref{no.uio.ifi.refaktor.change.executors}{Executor}.
\section{The Extract and Move Method Refactoring}
%The Extract and Move Method Refactoring is implemented mainly using these
unit\typeref{org.eclipse.jdt.core.ICompilationUnit}, the offset into the source
code where the extraction shall start, and the length of the source to be
extracted. Then you have to set the method name for the new method together with
-which access modifier that shall be used and some not so interesting parameters.
+its visibility and some not so interesting parameters.
\subsubsection{The MoveInstanceMethodProcessor Class}
-For the Move Method the processor requires a little more advanced input than
+For the Move Method, the processor requires a little more advanced input than
the class for the Extract Method. For construction it requires a method
-handle\typeref{org.eclipse.jdt.core.IMethod} from the Java Model for the method
-that is to be moved. Then the target for the move have to be supplied as the
-variable binding from a chosen variable declaration. In addition to this, one
-have to set some parameters regarding setters/getters and delegation.
+handle\typeref{org.eclipse.jdt.core.IMethod} for the method that is to be moved.
+Then the target for the move have to be supplied as the variable binding from a
+chosen variable declaration. In addition to this, one have to set some
+parameters regarding setters/getters, as well as delegation.
-To make a whole refactoring from the processor, one have to construct a
-\type{MoveRefactoring} from it.
+To make a working refactoring from the processor, one have to create a
+\type{MoveRefactoring} with it.
+
+\subsection{The ExtractAndMoveMethodChanger}
-\subsection{The ExtractAndMoveMethodChanger Class}
The \typewithref{no.uio.ifi.refaktor.changers}{ExtractAndMoveMethodChanger}
-class, that is a subclass of the class
-\typewithref{no.uio.ifi.refaktor.changers}{RefaktorChanger}, is the class
-responsible for composing the \type{ExtractMethodRefactoring} and the
-\type{MoveRefactoring}. Its constructor takes a project
-handle\typeref{org.eclipse.core.resources.IProject}, the method name for the new
-method and a \typewithref{no.uio.ifi.refaktor.utils}{SmartTextSelection}.
-
-A \type{SmartTextSelection} is basically a text
-selection\typeref{org.eclipse.jface.text.ITextSelection} object that enforces
-the providing of the underlying document during creation. I.e. its
-\methodwithref{no.uio.ifi.refaktor.utils.SmartTextSelection}{getDocument} method
-will never return \type{null}.
-
-Before extracting the new method, the possible targets for the move operation is
-found with the help of an
-\typewithref{no.uio.ifi.refaktor.extractors}{ExtractAndMoveMethodPrefixesExtractor}.
-The possible targets is computed from the prefixes that the extractor returns
-from its
-\methodwithref{no.uio.ifi.refaktor.extractors.ExtractAndMoveMethodPrefixesExtractor}{getSafePrefixes}
-method. The changer then choose the most suitable target by finding the most
-frequent occurring prefix among the safe ones. The target is the type of the
-first part of the prefix.
-
-After finding a suitable target, the \type{ExtractAndMoveMethodChanger} first
-creates an \type{ExtractMethodRefactoring} and performs it as explained in
-\myref{executing_refactoring} about the execution of refactorings. Then it
-creates and performs the \type{MoveRefactoring} in the same way, based on the
-changes done by the Extract Method refactoring.
-
-\subsection{The ExtractAndMoveMethodPrefixesExtractor Class}
-This extractor extracts properties needed for building the Extract and Move
-Method refactoring. It searches through the given selection to find safe
-prefixes, and those prefixes form a base that can be used to compute possible
-targets for the move part of the refactoring. It finds both the candidates, in
-the form of prefixes, and the non-candidates, called unfixes. All prefixes (and
-unfixes) are represented by a
+class is a subclass of the class
+\typewithref{no.uio.ifi.refaktor.changers}{RefaktorChanger}. It is responsible
+for analyzing and finding the best target for, and also executing, a composition
+of the Extract Method and Move Method refactorings. This particular changer is
+the one of my changers that is closest to being a true LTK refactoring. It can
+be reworked to be one if the problems with overlapping changes are resolved. The
+changer requires a text selection and the name of the new method, or else a
+method name will be generated. The selection has to be of the type
+\typewithref{no.uio.ifi.refaktor.utils}{CompilationUnitTextSelection}. This
+class is a custom extension to
+\typewithref{org.eclipse.jface.text}{TextSelection}, that in addition to the
+basic offset, length and similar methods, also carry an instance of the
+underlying compilation unit handle for the selection.
+
+\subsubsection{The \type{ExtractAndMoveMethodAnalyzer}}
+The analysis and precondition checking is done by the
+\typewithref{no.uio.ifi.refaktor.analyze.analyzers}{ExtractAnd\-MoveMethodAnalyzer}.
+First is check whether the selection is a valid selection or not, with respect
+to statement boundaries and that it actually contains any selections. Then it
+checks the legality of both extracting the selection and also moving it to
+another class. This checking of is performed by a range of checkers
+\see{checkers}. If the selection is approved as legal, it is analyzed to find
+the presumably best target to move the extracted method to.
+
+For finding the best suitable target the analyzer is using a
+\typewithref{no.uio.ifi.refaktor.analyze.collectors}{PrefixesCollector} that
+collects all the possible candidates for the refactoring. All the non-candidates
+is found by an
+\typewithref{no.uio.ifi.refaktor.analyze.collectors}{UnfixesCollector} that
+collects all the targets that will give some kind of error if used. (For
+details about the property collectors, se \myref{propertyCollectors}.) All
+prefixes (and unfixes) are represented by a
\typewithref{no.uio.ifi.refaktor.extractors}{Prefix}, and they are collected
-into prefix sets.\typeref{no.uio.ifi.refaktor.extractors.PrefixSet}.
-
-The prefixes and unfixes are found by property
-collectors\typeref{no.uio.ifi.refaktor.extractors.collectors.PropertyCollector}.
-A property collector follows the visitor pattern\citing{designPatterns} and is
-of the \typewithref{org.eclipse.jdt.core.dom}{ASTVisitor} type. An
-\type{ASTVisitor} visits nodes in an abstract syntax tree that forms the Java
-document object model. The tree consists of nodes of type
-\typewithref{org.eclipse.jdt.core.do}{ASTNode}.
-
-\subsubsection{The PrefixesCollector}
-The \typewithref{no.uio.ifi.refaktor.extractors.collectors}{PrefixesCollector}
-is of type \type{PropertyCollector}. It visits expression
-statements\typeref{org.eclipse.jdt.core.dom.ExpressionStatement} and creates
-prefixes from its expressions in the case of method invocations. The prefixes
-found is registered with a prefix set, together with all its sub-prefixes.
-\todo{Rewrite in the case of changes to the way prefixes are found}
+into sets of prefixes. The safe prefixes is found by subtracting from the set of
+candidate prefixes the prefixes that is enclosing any of the unfixes. A prefix
+is enclosing an unfix if the unfix is in the set of its sub-prefixes. As an
+example, \texttt{``a.b''} is enclosing \texttt{``a''}, as is \texttt{``a''}. The
+safe prefixes is unified in a \type{PrefixSet}. If a prefix has only one
+occurrence, and is a simple expression, it is considered unsuitable as a move
+target. This occurs in statements such as \texttt{``a.foo()''}. For such
+statements it bares no meaning to extract and move them. It only generates an
+extra method and the calling of it.
+
+The most suitable target for the refactoring is found by finding the prefix with
+the most occurrences. If two prefixes have the same occurrence count, but they
+differ in length, the longest of them is chosen.
+
+\todoin{Clean up sections/subsections.}
+
+\subsubsection{The \type{ExtractAndMoveMethodExecutor}}
+If the analysis finds a possible target for the composite refactoring, it is
+executed by an
+\typewithref{no.uio.ifi.refaktor.change.executors}{ExtractAndMoveMethodExecutor}.
+It is composed of the two executors known as
+\typewithref{no.uio.ifi.refaktor.change.executors}{ExtractMethodRefactoringExecutor}
+and
+\typewithref{no.uio.ifi.refaktor.change.executors}{MoveMethodRefactoringExecutor}.
+The \type{ExtractAndMoveMethodExecutor} is responsible for gluing the two
+together by feeding the \type{MoveMethod\-RefactoringExecutor} with the
+resources needed after executing the extract method refactoring.
+\See{postExtractExecution}
+
+\subsubsection{The \type{ExtractMethodRefactoringExecutor}}
+This executor is responsible for creating and executing an instance of the
+\type{ExtractMethodRefactoring} class. It is also responsible for collecting
+some post execution resources that can be used to find the method handle for the
+extracted method, as well as information about its parameters, including the
+variable they originated from.
+
+\subsubsection{The \type{MoveMethodRefactoringExecutor}}
+This executor is responsible for creating and executing an instance of the
+\type{MoveRefactoring}. The move refactoring is a processor-based refactoring,
+and for the Move Method refactoring it is the \type{MoveInstanceMethodProcessor}
+that is used.
+
+The handle for the method to be moved is found on the basis of the information
+gathered after the execution of the Extract Method refactoring. The only
+information the \type{ExtractMethodRefactoring} is sharing after its execution,
+regarding find the method handle, is the textual representation of the new
+method signature. Therefore it must be parsed, the strings for types of the
+parameters must be found and translated to a form that can be used to look up
+the method handle from its type handle. They have to be on the unresolved
+form.\todo{Elaborate?} The name for the type is found from the original
+selection, since an extracted method must end up in the same type as the
+originating method.
+
+When analyzing a selection prior to performing the Extract Method refactoring, a
+target is chosen. It has to be a variable binding, so it is either a field or a
+local variable/parameter. If the target is a field, it can be used with the
+\type{MoveInstanceMethodProcessor} as it is, since the extracted method still is
+in its scope. But if the target is local to the originating method, the target
+that is to be used for the processor must be among its parameters. Thus the
+target must be found among the extracted method's parameters. This is done by
+finding the parameter information object that corresponds to the parameter that
+was declared on basis of the original target's variable when the method was
+extracted. (The extracted method must take one such parameter for each local
+variable that is declared outside the selection that is extracted.) To match the
+original target with the correct parameter information object, the key for the
+information object is compared to the key from the original target's binding.
+The source code must then be parsed to find the method declaration for the
+extracted method. The new target must be found by searching through the
+parameters of the declaration and choose the one that has the same type as the
+old binding from the parameter information object, as well as the same name that
+is provided by the parameter information object.
+
+
+\subsection{The
+SearchBasedExtractAndMoveMethodChanger}\label{searchBasedExtractAndMoveMethodChanger}
+\todoin{Write\ldots}
+
+\subsection{Finding the IMethod}\label{postExtractExecution}
+\todoin{Rename section. Write??}
-\subsubsection{The UnfixesCollector}
-The \typewithref{no.uio.ifi.refaktor.extractors.collectors}{UnfixesCollector}
-finds unfixes within the selection. An unfix is a name that is assigned to
-within the selection. The reason that this cannot be allowed, is that the result
-would be an assignment to the \type{this} keyword, which is not valid in Java.
-
-\subsubsection{Computing Safe Prefixes}
-A safe prefix is a prefix that does not enclose an unfix. A prefix is enclosing
-an unfix if the unfix is in the set of its sub-prefixes. As an example,
-\texttt{``a.b''} is enclosing \texttt{``a''}, as is \texttt{``a''}. The safe
-prefixes is unified in a \type{PrefixSet} and can be fetched calling the
-\method{getSafePrefixes} method of the
-\type{ExtractAndMoveMethodPrefixesExtractor}.
\subsection{The Prefix Class}
-\todo{?}
+This class exists mainly for holding data about a prefix, such as the expression
+that the prefix represents and the occurrence count of the prefix within a
+selection. In addition to this, it has some functionality such as calculating
+its sub-prefixes and intersecting it with another prefix. The definition of the
+intersection between two prefixes is a prefix representing the longest common
+expression between the two.
+
\subsection{The PrefixSet Class}
+A prefix set holds elements of type \type{Prefix}. It is implemented with the
+help of a \typewithref{java.util}{HashMap} and contains some typical set
+operations, but it does not implement the \typewithref{java.util}{Set}
+interface, since the prefix set does not need all of the functionality a
+\type{Set} requires to be implemented. In addition It needs some other
+functionality not found in the \type{Set} interface. So due to the relatively
+limited use of prefix sets, and that it almost always needs to be referenced as
+such, and not a \type{Set<Prefix>}, it remains as an ad hoc solution to a
+concrete problem.
+
+There are two ways adding prefixes to a \type{PrefixSet}. The first is through
+its \method{add} method. This works like one would expect from a set. It adds
+the prefix to the set if it does not already contain the prefix. The other way
+is to \emph{register} the prefix with the set. When registering a prefix, if the
+set does not contain the prefix, it is just added. If the set contains the
+prefix, its count gets incremented. This is how the occurrence count is handled.
+
+The prefix set also computes the set of prefixes that is not enclosing any
+prefixes of another set. This is kind of a set difference operation only for
+enclosing prefixes.
\subsection{Hacking the Refactoring Undo
History}\label{hacking_undo_history}
-\todo{Where to put this section?}
+\todoin{Where to put this section?}
As an attempt to make multiple subsequent changes to the workspace appear as a
single action (i.e. make the undo changes appear as such), I tried to alter
+
+\chapter{Analyzing Source Code in Eclipse}
+
+\section{The Java model}\label{javaModel}
+The Java model of Eclipse is its internal representation of a Java project. It
+is light-weight, and has only limited possibilities for manipulating source
+code. It is typically used as a basis for the Package Explorer in Eclipse.
+
+The elements of the Java model is only handles to the underlying elements. This
+means that the underlying element of a handle does not need to actually exist.
+Hence the user of a handle must always check that it exist by calling the
+\method{exists} method of the handle.
+
+The handles with descriptions is listed in \myref{tab:javaModel}.
+
+\begin{table}[h]
+ \centering
+
+ \newcolumntype{L}[1]{>{\hsize=#1\hsize\raggedright\arraybackslash}X}%
+ % sum must equal number of columns (3)
+ \begin{tabularx}{\textwidth}{| L{0.7} | L{1.1} | L{1.2} |}
+ \hline
+ \textbf{Project Element} & \textbf{Java Model element} &
+ \textbf{Description} \\
+ \hline
+ Java project & \type{IJavaProject} & The Java project which contains all other objects. \\
+ \hline
+ Source folder /\linebreak[2] binary folder /\linebreak[3] external library &
+ \type{IPackageFragmentRoot} & Hold source or binary files, can be a folder
+ or a library (zip / jar file). \\
+ \hline
+ Each package & \type{IPackageFragment} & Each package is below the
+ \type{IPackageFragmentRoot}, sub-packages are not leaves of the package,
+ they are listed directed under \type{IPackageFragmentRoot}. \\
+ \hline
+ Java Source file & \type{ICompilationUnit} & The Source file is always below
+ the package node. \\
+ \hline
+ Types /\linebreak[2] Fields /\linebreak[3] Methods & \type{IType} /
+ \linebreak[0]
+ \type{IField} /\linebreak[3] \type{IMethod} & Types, fields and methods. \\
+ \hline
+ \end{tabularx}
+ \caption{The elements of the Java Model. {\footnotesize Taken from
+ \url{http://www.vogella.com/tutorials/EclipseJDT/article.html}}}
+ \label{tab:javaModel}
+\end{table}
+
+The hierarchy of the Java Model is shown in \myref{fig:javaModel}.
+
+\begin{figure}[h]
+ \centering
+ \begin{tikzpicture}[%
+ grow via three points={one child at (0,-0.7) and
+ two children at (0,-0.7) and (0,-1.4)},
+ edge from parent path={(\tikzparentnode.south west)+(0.5,0) |-
+ (\tikzchildnode.west)}]
+ \tikzstyle{every node}=[draw=black,thick,anchor=west]
+ \tikzstyle{selected}=[draw=red,fill=red!30]
+ \tikzstyle{optional}=[dashed,fill=gray!50]
+ \node {\type{IJavaProject}}
+ child { node {\type{IPackageFragmentRoot}}
+ child { node {\type{IPackageFragment}}
+ child { node {\type{ICompilationUnit}}
+ child { node {\type{IType}}
+ child { node {\type{\{ IType \}*}}
+ child { node {\type{\ldots}}}
+ }
+ child [missing] {}
+ child { node {\type{\{ IField \}*}}}
+ child { node {\type{IMethod}}
+ child { node {\type{\{ IType \}*}}
+ child { node {\type{\ldots}}}
+ }
+ }
+ child [missing] {}
+ child [missing] {}
+ child { node {\type{\{ IMethod \}*}}}
+ }
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child { node {\type{\{ IType \}*}}}
+ }
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child { node {\type{\{ ICompilationUnit \}*}}}
+ }
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child { node {\type{\{ IPackageFragment \}*}}}
+ }
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child [missing] {}
+ child { node {\type{\{ IPackageFragmentRoot \}*}}}
+ ;
+ \end{tikzpicture}
+ \caption{The Java model of Eclipse. ``\type{\{ SomeElement \}*}'' means
+ \type{SomeElement} zero or more times. For recursive structures,
+ ``\type{\ldots}'' is used.}
+ \label{fig:javaModel}
+\end{figure}
+
+\section{The Abstract Synax Tree}
+Eclipse is following the common paradigm of using an abstract syntaxt tree for
+source code analysis and manipulation.
+
+When parsing program source code into something that can be used as a foundation
+for analysis, the start of the process follows the same steps as in a compiler.
+This is all natural, because the way a compiler anayzes code is no different
+from how source manipulation programs would do it, except for some properties of
+code that is analyzed in the parser, and that they may be differing in what
+kinds of properties they analyze. Thus the process of translation source code
+into a structure that is suitable for analyzing, can be seen as a kind of
+interrupted compilation process \see{fig:interruptedCompilationProcess}.
+
+\begin{figure}[h]
+ \centering
+ \tikzset{
+ base/.style={anchor=north, align=center, rectangle, minimum height=1.4cm},
+ basewithshadow/.style={base, drop shadow, fill=white},
+ outlined/.style={basewithshadow, draw, rounded corners, minimum
+ width=0.4cm},
+ primary/.style={outlined, font=\bfseries},
+ dashedbox/.style={outlined, dashed},
+ arrowpath/.style={black, align=center, font=\small},
+ processarrow/.style={arrowpath, ->, >=angle 90, shorten >=1pt},
+ }
+ \begin{tikzpicture}[node distance=1.3cm and 3cm, scale=1, every
+ node/.style={transform shape}]
+ \node[base](AuxNode1){\small source code};
+ \node[primary, right=of AuxNode1, xshift=-2.5cm](Scanner){Scanner};
+ \node[primary, right=of Scanner, xshift=0.5cm](Parser){Parser};
+ \node[dashedbox, below=of Parser](SemanticAnalyzer){Semantic\\Analyzer};
+ \node[dashedbox, left=of SemanticAnalyzer](SourceCodeOptimizer){Source
+ Code\\Optimizer};
+ \node[dashedbox, below=of SourceCodeOptimizer
+ ](CodeGenerator){Code\\Generator};
+ \node[dashedbox, right=of CodeGenerator](TargetCodeOptimizer){Target
+ Code\\Optimizer};
+ \node[base, right=of TargetCodeOptimizer](AuxNode2){};
+
+ \draw[processarrow](AuxNode1) -- (Scanner);
+
+ \path[arrowpath] (Scanner) -- node [sloped](tokens){tokens}(Parser);
+ \draw[processarrow](Scanner) -- (tokens) -- (Parser);
+
+ \path[arrowpath] (Parser) -- node (syntax){syntax
+ tree}(SemanticAnalyzer);
+ \draw[processarrow](Parser) -- (syntax) -- (SemanticAnalyzer);
+
+ \path[arrowpath] (SemanticAnalyzer) -- node
+ [sloped](annotated){annotated\\tree}(SourceCodeOptimizer);
+ \draw[processarrow, dashed](SemanticAnalyzer) -- (annotated) --
+ (SourceCodeOptimizer);
+
+ \path[arrowpath] (SourceCodeOptimizer) -- node
+ (intermediate){intermediate code}(CodeGenerator);
+ \draw[processarrow, dashed](SourceCodeOptimizer) -- (intermediate) --
+ (CodeGenerator);
+
+ \path[arrowpath] (CodeGenerator) -- node [sloped](target1){target
+ code}(TargetCodeOptimizer);
+ \draw[processarrow, dashed](CodeGenerator) -- (target1) --
+ (TargetCodeOptimizer);
+
+ \path[arrowpath](TargetCodeOptimizer) -- node [sloped](target2){target
+ code}(AuxNode2);
+ \draw[processarrow, dashed](TargetCodeOptimizer) -- (target2) (AuxNode2);
+ \end{tikzpicture}
+ \caption{Interrupted compilation process. {\footnotesize (Full compilation
+ process borrowed from \emph{Compiler construction: principles and practice}
+ by Kenneth C. Louden\citing{louden1997}.)}}
+ \label{fig:interruptedCompilationProcess}
+\end{figure}
+
+The process starts with a \emph{scanner}, or lexer. The job of the scanner is to
+read the source code and divide it into tokens for the parser. Therefore, it is
+also sometimes called a tokenizer. A token is a logical unit, defined in the
+language specification, consisting of one or more consecutive characters. In
+the java language the tokens can for instance be the \var{this} keyword, a curly
+bracket \var{\{} or a \var{nameToken}. It is recognized by the scanner on the
+basis of something eqivalent of a regular expression. This part of the process
+is often implemented with the use of a finite automata. In fact, it is common to
+specify the tokens in regular expressions, that in turn is translated into a
+finite automata lexer. This process can be automated.
+
+The program component used to translate a a stream of tokens into something
+meaningful, is called a parser. A parser is fed tokens from the scanner and
+performs an analysis of the structure of a program. It verifies that the syntax
+is correct according to the grammar rules of a language, that is usually
+specified in a context-free grammar, and often in a variant of the
+\emph{Backus--Naur
+Form}\footnote{\url{https://en.wikipedia.org/wiki/Backus-Naur\_Form}}. The
+result coming from the parser is in the form of an \emph{Abstract Syntax Tree},
+AST for short. It is called \emph{abstract}, because the structure does not
+contain all of the tokens produced by the scanner. It only contain logical
+constructs, and because it forms a tree, all kinds of parentheses and brackets
+are implicit in the structure. It is this AST that is used when performing the
+semantic analysis of the code.
+
+As an example we can think of the expression \code{(5 + 7) * 2}. The root of
+this tree would in Eclipse be an \type{InfixExpression} with the operator
+\var{TIMES}, and a left operand that is also an \type{InfixExpression} with the
+operator \var{PLUS}. The left operand \type{InfixExpression}, has in turn a left
+operand of type \type{NumberLiteral} with the value \var{``5''} and a right
+operand \type{NumberLiteral} with the value \var{``7''}. The root will have a
+right operand of type \type{NumberLiteral} and value \var{``2''}. The AST for
+this expression is illustrated in \myref{fig:astInfixExpression}.
+
+Contrary to the Java Model, an abstract syntaxt tree is a heavy-weight
+representation of source code. It contains information about propertes like type
+bindings for variables and variable bindings for names.
+
+
+\begin{figure}[h]
+ \centering
+ \begin{tikzpicture}[scale=0.8]
+ \tikzset{level distance=40pt}
+ \tikzset{sibling distance=5pt}
+ \tikzstyle{thescale}=[scale=0.8]
+ \tikzset{every tree node/.style={align=center}}
+ \tikzset{edge from parent/.append style={thick}}
+ \tikzstyle{inode}=[rectangle,rounded corners,draw,fill=lightgray,drop
+ shadow,align=center]
+ \tikzset{every internal node/.style={inode}}
+ \tikzset{every leaf node/.style={draw=none,fill=none}}
+
+ \Tree [.\type{InfixExpression} [.\type{InfixExpression}
+ [.\type{NumberLiteral} \var{``5''} ] [.\type{Operator} \var{PLUS} ]
+ [.\type{NumberLiteral} \var{``7''} ] ]
+ [.\type{Operator} \var{TIMES} ]
+ [.\type{NumberLiteral} \var{``2''} ]
+ ]
+ \end{tikzpicture}
+ \caption{The abstract syntax tree for the expression \code{(5 + 7) * 2}.}
+ \label{fig:astInfixExpression}
+\end{figure}
+
+\subsection{The AST in Eclipse}
+In Eclipse, every node in the AST is a child of the abstract superclass
+\typewithref{org.eclipse.jdt.core.dom}{ASTNode}. Every \type{ASTNode}, among a
+lot of other things, provides information about its position and length in the
+source code, as well as a reference to its parent and to the root of the tree.
+
+The root of the AST is always of type \type{CompilationUnit}. It is not the same
+as an instance of an \type{ICompilationUnit}, which is the compilation unit
+handle of the Java model. The children of a \type{CompilationUnit} is an
+optional \type{PackageDeclaration}, zero or more nodes of type
+\type{ImportDecaration} and all its top-level type declarations that has node
+types \type{AbstractTypeDeclaration}.
+
+An \type{AbstractType\-Declaration} can be one of the types
+\type{AnnotationType\-Declaration}, \type{Enum\-Declaration} or
+\type{Type\-Declaration}. The children of an \type{AbstractType\-Declaration}
+must be a subtype of a \type{BodyDeclaration}. These subtypes are:
+\type{AnnotationTypeMember\-Declaration}, \type{EnumConstant\-Declaration},
+\type{Field\-Declaration}, \type{Initializer} and \type{Method\-Declaration}.
+
+Of the body declarations, the \type{Method\-Declaration} is the most interesting
+one. Its children include lists of modifiers, type parameters, parameters and
+exceptions. It has a return type node and a body node. The body, if present, is
+of type \type{Block}. A \type{Block} is itself a \type{Statement}, and its
+children is a list of \type{Statement} nodes.
+
+There are too many types of the abstract type \type{Statement} to list up, but
+there exists a subtype of \type{Statement} for every statement type of Java, as
+one would expect. This also applies to the abstract type \type{Expression}.
+However, the expression \type{Name} is a little special, since it is both used
+as an operand in compound expressions, as well as for names in type declarations
+and such.
+
+There is an overview of some of the structure of an Eclipse AST in
+\myref{fig:astEclipse}.
+
+\begin{figure}[h]
+ \centering
+ \begin{tikzpicture}[scale=0.8]
+ \tikzset{level distance=50pt}
+ \tikzset{sibling distance=5pt}
+ \tikzstyle{thescale}=[scale=0.8]
+ \tikzset{every tree node/.style={align=center}}
+ \tikzset{edge from parent/.append style={thick}}
+ \tikzstyle{inode}=[rectangle,rounded corners,draw,fill=lightgray,drop
+ shadow,align=center]
+ \tikzset{every internal node/.style={inode}}
+ \tikzset{every leaf node/.style={draw=none,fill=none}}
+
+ \Tree [.\type{CompilationUnit} [.\type{[ PackageDeclaration ]} [.\type{Name} ]
+ [.\type{\{ Annotation \}*} ] ]
+ [.\type{\{ ImportDeclaration \}*} [.\type{Name} ] ]
+ [.\type{\{ AbstractTypeDeclaration \}+} [.\node(site){\type{\{
+ BodyDeclaration \}*}}; ] [.\type{SimpleName} ] ]
+ ]
+ \begin{scope}[shift={(0.5,-6)}]
+ \node[inode,thescale](root){\type{MethodDeclaration}};
+ \node[inode,thescale](modifiers) at (4.5,-5){\type{\{ IExtendedModifier \}*}
+ \\ {\footnotesize (Of type \type{Modifier} or \type{Annotation})}};
+ \node[inode,thescale](typeParameters) at (-6,-3.5){\type{\{ TypeParameter
+ \}*}};
+ \node[inode,thescale](parameters) at (-5,-5){\type{\{
+ SingleVariableDeclaration \}*} \\ {\footnotesize (Parameters)}};
+ \node[inode,thescale](exceptions) at (5,-3){\type{\{ Name \}*} \\
+ {\footnotesize (Exceptions)}};
+ \node[inode,thescale](return) at (-6.5,-2){\type{Type} \\ {\footnotesize
+ (Return type)}};
+ \begin{scope}[shift={(0,-5)}]
+ \Tree [.\node(body){\type{[ Block ]} \\ {\footnotesize (Body)}};
+ [.\type{\{ Statement \}*} [.\type{\{ Expression \}*} ]
+ [.\type{\{ Statement \}*} [.\type{\ldots} ]]
+ ]
+ ]
+ \end{scope}
+ \end{scope}
+ \draw[->,>=triangle 90,shorten >=1pt](root.east)..controls +(east:2) and
+ +(south:1)..(site.south);
+
+ \draw (root.south) -- (modifiers);
+ \draw (root.south) -- (typeParameters);
+ \draw (root.south) -- ($ (parameters.north) + (2,0) $);
+ \draw (root.south) -- (exceptions);
+ \draw (root.south) -- (return);
+ \draw (root.south) -- (body);
+
+ \end{tikzpicture}
+ \caption{The format of the abstract syntax tree in Eclipse.}
+ \label{fig:astEclipse}
+\end{figure}
+\todoin{Add more to the AST format tree? \myref{fig:astEclipse}}
+
+\section{The ASTVisitor}\label{astVisitor}
+So far, the only thing that has been adressed is how the the data that is going
+to be the basis for our analysis is structured. Another aspect of it is how we
+are going to traverse the AST to gather the information we need, so we can
+conclude about the properties we are analysing. It is of course possible to
+start at the top of the tree, and manually search through its nodes for the ones
+we are looking for, but that is a bit inconvenient. To be able to efficiently
+utilize such an approach, we would need to make our own framework for traversing
+the tree and visiting only the types of nodes we are after. Luckily, this
+functionality is already provided in Eclipse, by its
+\typewithref{org.eclipse.jdt.core.dom}{ASTVisitor}.
+
+The Eclipse AST, together with its \type{ASTVisitor}, follows the \emph{Visitor}
+pattern\citing{designPatterns}. The intent of this design pattern is to
+facilitate extending the functionality of classes without touching the classes
+themselves.
+
+Let us say that there is a class hierarchy of \emph{Elements}. These elements
+all have a method \method{accept(Visitor visitor)}. In its simplest form, the
+\method{accept} method just calls the \method{visit} method of the visitor with
+itself as an argument, like this: \code{visitor.visit(this)}. For the visitors
+to be able to extend the functionality of all the classes in the elements
+hierarchy, each \type{Visitor} must have one visit method for each concrete
+class in the hierarchy. Say the hierarchy consists of the concrete classes
+\type{ConcreteElementA} and \type{ConcreteElementB}. Then each visitor must have
+the (possibly empty) methods \method{visit(ConcreteElementA element)} and
+\method{visit(ConcreteElementB element)}. This scenario is depicted in
+\myref{fig:visitorPattern}.
+
+\begin{figure}[h]
+ \centering
+ \tikzstyle{abstract}=[rectangle, draw=black, fill=white, drop shadow, text
+ centered, anchor=north, text=black, text width=6cm, every one node
+part/.style={align=center, font=\bfseries\itshape}]
+ \tikzstyle{concrete}=[rectangle, draw=black, fill=white, drop shadow, text
+ centered, anchor=north, text=black, text width=6cm]
+ \tikzstyle{inheritarrow}=[->, >=open triangle 90, thick]
+ \tikzstyle{commentarrow}=[->, >=angle 90, dashed]
+ \tikzstyle{line}=[-, thick]
+ \tikzset{every one node part/.style={align=center, font=\bfseries}}
+ \tikzset{every second node part/.style={align=center, font=\ttfamily}}
+
+ \begin{tikzpicture}[node distance=1cm, scale=0.8, every node/.style={transform
+ shape}]
+ \node (Element) [abstract, rectangle split, rectangle split parts=2]
+ {
+ \nodepart{one}{Element}
+ \nodepart{second}{+accept(visitor: Visitor)}
+ };
+ \node (AuxNode01) [text width=0, minimum height=2cm, below=of Element] {};
+ \node (ConcreteElementA) [concrete, rectangle split, rectangle split
+ parts=2, left=of AuxNode01]
+ {
+ \nodepart{one}{ConcreteElementA}
+ \nodepart{second}{+accept(visitor: Visitor)}
+ };
+ \node (ConcreteElementB) [concrete, rectangle split, rectangle split
+ parts=2, right=of AuxNode01]
+ {
+ \nodepart{one}{ConcreteElementB}
+ \nodepart{second}{+accept(visitor: Visitor)}
+ };
+
+ \node[comment, below=of ConcreteElementA] (CommentA) {visitor.visit(this)};
+
+ \node[comment, below=of ConcreteElementB] (CommentB) {visitor.visit(this)};
+
+ \node (AuxNodeX) [text width=0, minimum height=1cm, below=of AuxNode01] {};
+
+ \node (Visitor) [abstract, rectangle split, rectangle split parts=2,
+ below=of AuxNodeX]
+ {
+ \nodepart{one}{Visitor}
+ \nodepart{second}{+visit(ConcreteElementA)\\+visit(ConcreteElementB)}
+ };
+ \node (AuxNode02) [text width=0, minimum height=2cm, below=of Visitor] {};
+ \node (ConcreteVisitor1) [concrete, rectangle split, rectangle split
+ parts=2, left=of AuxNode02]
+ {
+ \nodepart{one}{ConcreteVisitor1}
+ \nodepart{second}{+visit(ConcreteElementA)\\+visit(ConcreteElementB)}
+ };
+ \node (ConcreteVisitor2) [concrete, rectangle split, rectangle split
+ parts=2, right=of AuxNode02]
+ {
+ \nodepart{one}{ConcreteVisitor2}
+ \nodepart{second}{+visit(ConcreteElementA)\\+visit(ConcreteElementB)}
+ };
+
+
+ \draw[inheritarrow] (ConcreteElementA.north) -- ++(0,0.7) -|
+ (Element.south);
+ \draw[line] (ConcreteElementA.north) -- ++(0,0.7) -|
+ (ConcreteElementB.north);
+
+ \draw[inheritarrow] (ConcreteVisitor1.north) -- ++(0,0.7) -|
+ (Visitor.south);
+ \draw[line] (ConcreteVisitor1.north) -- ++(0,0.7) -|
+ (ConcreteVisitor2.north);
+
+ \draw[commentarrow] (CommentA.north) -- (ConcreteElementA.south);
+ \draw[commentarrow] (CommentB.north) -- (ConcreteElementB.south);
+
+
+ \end{tikzpicture}
+ \caption{The Visitor Pattern.}
+ \label{fig:visitorPattern}
+\end{figure}
+
+The use of the visitor pattern can be appropriate when the hierarchy of elements
+is mostly stable, but the family of operations over its elements is constantly
+growing. This is clearly the cas for the Eclipse AST, since the hierarchy of
+type \type{ASTNode} is very stable, but the functionality of its elements is
+extended every time someone needs to operate on the AST. Another aspect of the
+Eclipse implementation is that it is a public API, and the visitor pattern is an
+easy way to provide access to the nodes in the tree.
+
+The version of the visitor pattern implemented for the AST nodes in Eclipse also
+provides an elegant way to traverse the tree. It does so by following the
+convention that every node in the tree first let the visitor visit itself,
+before it also makes all its children accept the visitor. The children are only
+visited if the visit method of their parent returns \var{true}. This pattern
+then makes for a prefix traversal of the AST. If postfix traversal is desired,
+the visitors also has \method{endVisit} methods for each node type, that is
+called after the \method{visit} method for a node. In addition to these visit
+methods, there are also the methods \method{preVisit(ASTNode)},
+\method{postVisit(ASTNode)} and \method{preVisit2(ASTNode)}. The
+\method{preVisit} method is called before the type-specific \method{visit}
+method. The \method{postVisit} method is called after the type-specific
+\method{endVisit}. The type specific \method{visit} is only called if
+\method{preVisit2} returns \var{true}. Overriding the \method{preVisit2} is also
+altering the behavior of \method{preVisit}, since the default implementation is
+responsible for calling it.
+
+An example of a trivial \type{ASTVisitor} is shown in
+\myref{lst:astVisitorExample}.
+
+\begin{listing}
+\begin{minted}{java}
+public class CollectNamesVisitor extends ASTVisitor {
+ Collection<Name> names = new LinkedList<Name>();
+
+ @Override
+ public boolean visit(QualifiedName node) {
+ names.add(node);
+ return false;
+ }
+
+ @Override
+ public boolean visit(SimpleName node) {
+ names.add(node);
+ return true;
+ }
+}
+\end{minted}
+\caption{An \type{ASTVisitor} that visits all the names in a subtree and adds
+them to a collection, except those names that are children of any
+\type{QualifiedName}.}
+\label{lst:astVisitorExample}
+\end{listing}
+
+\section{Property collectors}\label{propertyCollectors}
+The prefixes and unfixes are found by property
+collectors\typeref{no.uio.ifi.refaktor.extractors.collectors.PropertyCollector}.
+A property collector is of the \type{ASTVisitor} type, and thus visits nodes of
+type \type{ASTNode} of the abstract syntax tree \see{astVisitor}.
+
+\subsection{The PrefixesCollector}
+The \typewithref{no.uio.ifi.refaktor.extractors.collectors}{PrefixesCollector}
+finds prefixes that makes up the basis for calculating move targets for the
+Extract and Move Method refactoring. It visits expression
+statements\typeref{org.eclipse.jdt.core.dom.ExpressionStatement} and creates
+prefixes from its expressions in the case of method invocations. The prefixes
+found is registered with a prefix set, together with all its sub-prefixes.
+
+\subsection{The UnfixesCollector}\label{unfixes}
+The \typewithref{no.uio.ifi.refaktor.extractors.collectors}{UnfixesCollector}
+finds unfixes within a selection. That is prefixes that cannot be used as a
+basis for finding a move target in a refactoring.
+
+An unfix can be a name that is assigned to within a selection. The reason that
+this cannot be allowed, is that the result would be an assignment to the
+\type{this} keyword, which is not valid in Java \see{eclipse_bug_420726}.
+
+Prefixes that originates from variable declarations within the same selection
+are also considered unfixes. This is because when a method is moved, it needs to
+be called through a variable. If this variable is also within the method that is
+to be moved, this obviously cannot be done.
+
+Also considered as unfixes are variable references that are of types that is not
+suitable for moving a methods to. This can be either because it is not
+physically possible to move the method to the desired class or that it will
+cause compilation errors by doing so.
+
+If the type binding for a name is not resolved it is considered and unfix. The
+same applies to types that is only found in compiled code, so they have no
+underlying source that is accessible to us. (E.g. the \type{java.lang.String}
+class.)
+
+Interfaces types are not suitable as targets. This is simply because interfaces
+in java cannot contain methods with bodies. (This thesis does not deal with
+features of Java versions later than Java 7. Java 8 has interfaces with default
+implementations of methods.) Neither are local types allowed. This accounts for
+both local and anonymous classes. Anonymous classes are effectively the same as
+interface types with respect to unfixes. Local classes could in theory be used
+as targets, but this is not possible due to limitations of the implementation of
+the Extract and Move Method refactoring. The problem is that the refactoring is
+done in two steps, so the intermediate state between the two refactorings would
+not be legal Java code. In the case of local classes, the problem is that, in
+the intermediate step, a selection referencing a local class would need to take
+the local class as a parameter if it were to be extracted to a new method. This
+new method would need to live in the scope of the declaring class of the
+originating method. The local class would then not be in the scope of the
+extracted method, thus bringing the source code into an illegal state. One could
+imagine that the method was extracted and moved in one operation, without an
+intermediate state. Then it would make sense to include variables with types of
+local classes in the set of legal targets, since the local classes would then be
+in the scopes of the method calls. If this makes any difference for software
+metrics that measure coupling would be a different discussion.
+
+\begin{listing}
+\begin{multicols}{2}
+\begin{minted}[]{java}
+// Before
+void declaresLocalClass() {
+ class LocalClass {
+ void foo() {}
+ void bar() {}
+ }
+
+ LocalClass inst =
+ new LocalClass();
+ inst.foo();
+ inst.bar();
+}
+\end{minted}
+
+\columnbreak
+
+\begin{minted}[]{java}
+// After Extract Method
+void declaresLocalClass() {
+ class LocalClass {
+ void foo() {}
+ void bar() {}
+ }
+
+ LocalClass inst =
+ new LocalClass();
+ fooBar(inst);
+}
+
+// Intermediate step
+void fooBar(LocalClass inst) {
+ inst.foo();
+ inst.bar();
+}
+\end{minted}
+\end{multicols}
+\caption{When Extract and Move Method tries to use a variable with a local type
+as the move target, an intermediate step is taken that is not allowed. Here:
+\type{LocalClass} is not in the scope of \method{fooBar} in its intermediate
+location.}
+\label{lst:extractMethod_LocalClass}
+\end{listing}
+
+The last class of names that are considered unfixes is names used in null tests.
+These are tests that reads like this: if \texttt{<name>} equals \var{null} then
+do something. If allowing variables used in those kinds of expressions as
+targets for moving methods, we would end up with code containing boolean
+expressions like \texttt{this == null}, which would not be meaningful, since
+\var{this} would never be \var{null}.
+
+
+\subsection{The ContainsReturnStatementCollector}
+The
+\typewithref{no.uio.ifi.refaktor.analyze.collectors}{ContainsReturnStatementCollector}
+is a very simple property collector. It only visits the return statements within
+a selection, and can report whether it encountered a return statement or not.
+
+\subsection{The LastStatementCollector}
+The \typewithref{no.uio.ifi.refaktor.analyze.collectors}{LastStatementCollector}
+collects the last statement of a selection. It does so by only visiting the top
+level statements of the selection, and compares the textual end offset of each
+encuntered statement with the end offset of the previous statement found.
+
+\section{Checkers}\label{checkers}
+The checkers are a range of classes that checks that selections complies with
+certian criterias. If a
+\typewithref{no.uio.ifi.refaktor.analyze.analyzers}{Checker} fails, it throws a
+\type{CheckerException}. The checkers are managed by the
+\type{LegalStatementsChecker}, which does not, in fact, implement the
+\type{Checker} interface. It does, however, run all the checkers registered with
+it, and reports that all statements are considered legal if no
+\type{CheckerException} is thrown. Many of the checkers either extends the
+\type{PropertyCollector} or utilizes one or more property collectors to verify
+some criterias. The checkers registered with the \type{LegalStatementsChecker}
+are described next. They are run in the order presented below.
+
+\subsection{The EnclosingInstanceReferenceChecker}
+The purpose of this checker is to verify that the names in a selection is not
+referencing any enclosing instances. This is for making sure that all references
+is legal in a method that is to be moved. Theoretically, some situations could
+be easily solved my passing a reference to the referenced class with the moved
+method (e.g. when calling public methods), but the dependency on the
+\type{MoveInstanceMethodProcessor} prevents this.
+
+The
+\typewithref{no.uio.ifi.refaktor.analyze.analyzers}{EnclosingInstanceReferenceChecker}
+is a modified version of the
+\typewithref{org.eclipse.jdt.internal.corext.refactoring.structure.MoveInstanceMethodProcessor}{EnclosingInstanceReferenceFinder}
+from the \type{MoveInstanceMethodProcessor}. Wherever the
+\type{EnclosingInstanceReferenceFinder} would create a fatal error status, the
+checker throws a \type{CheckerException}.
+
+It works by first finding all of the enclosing types of a selection. Thereafter
+it visits all its simple names to check that they are not references to
+variables or methods declared in any of the enclosing types. In addition the
+checker visits \var{this}-expressions to verify that no such expressions is
+qualified with any name.
+
+\subsection{The ReturnStatementsChecker}\label{returnStatementsChecker}
+\todoin{Write\ldots/change implementation/use control flow graph?}
+
+\subsection{The AmbiguousReturnValueChecker}
+This checker verifies that there are no \emph{ambiguous return statements} in a
+selection. The problem with ambiguous return statements arise when a selection
+is chosen to be extracted into a new method, but it needs to return more than
+one value from that method. This problem occurs in two situations. The first
+situation arise when there is more than one local variable that is both assigned
+to within a selection and also referenced after the selection. The other
+situation occur when there is only one such assignment, but there is also one or
+more return statements in the selection.
+
+First the checker needs to collect some data. Those data are the binding keys
+for all simple names that are assigned to within the selection, including
+variable declarations, but excluding fields. The checker also collects whether
+there exists a return statement in the selection or not. No further checks of
+return statements are needed, since, at this point, the selection is already
+checked for illegal return statements \see{returnStatementsChecker}.
+
+After the binding keys of the assignees are collected, the checker searches the
+part of the enclosing method that is after the selection for references whose
+binding keys are among the the collected keys. If more than one unique referral
+is found, or only one referral is found, but the selection also contains a
+return statement, we have a situation with an ambiguous return value, and an
+exception is thrown.
+
+%\todoin{Explain why we do not need to consider variables assigned inside
+%local/anonymous classes. (The referenced variables need to be final and so
+%on\ldots)}
+
+\subsection{The IllegalStatementsChecker}
+This checker is designed to check for illegal statements.
+
+Any use of the \var{super} keyword is prohibited, since its meaning is altered
+when moving a method to another class.
+
+For a \emph{break} statement, there is two situations to consider: A break
+statement with or without a label. If the break statement has a label, it is
+checked that whole of the labeled statement is inside the selection. Since a
+label does not have any binding information, we have to search upwards in the
+AST to find the \type{LabeledStatement} that corresponds to the label from the
+break statement, and check that it is contained in the selection. If the break
+statement does not have a label attached to it, it is checked that its innermost
+enclosing loop or switch statement also is inside the selection.
+
+The situation for a \emph{continue} statement is the same as for a break
+statement, except that it is not allowed inside switch statements.
+
+Regarding \emph{assignments}, two types of assignments is allowed: Assignment to
+a non-final variable and assignment to an array access. All other assignments is
+regarded illegal.
+
+\todoin{Finish\ldots}
+
+
+\chapter{Benchmarking}
+\todoin{Better name than ``benchmarking''?}
+This part of the master project is located in the Eclipse project
+\code{no.uio.ifi.refaktor.benchmark}. The purpose of it is to run the equivalent
+of the \type{SearchBasedExtractAndMoveMethodChanger}
+\see{searchBasedExtractAndMoveMethodChanger} over a larger software project,
+both to test its roubustness but also its effect on different software metrics.
+
+\section{The benchmark setup}
+The benchmark itself is set up as a \emph{JUnit} test case. This is a convenient
+setup, and utilizes the \emph{JUnit Plugin Test Launcher}. This provides us a
+with a fully functional Eclipse workbench. Most importantly, this gives us
+access to the Java Model of Eclipse \see{javaModel}.
+
+\subsection{The ProjectImporter}
+The Java project that is going to be used as the data for the benchmark, must be
+imported into the JUnit workspace. This is done by the
+\typewithref{no.uio.ifi.refaktor.benchmark}{ProjectImporter}. The importer
+require the absolute path to the project description file. It is named
+\code{.project} and is located at the root of the project directory.
+
+The project description is loaded to find the name of the project to be
+imported. The project that shall be the destination for the import is created in
+the workspace, on the base of the name from the description. Then an import
+operation is created, based on both the source and destination information. The
+import operation is run to perform the import.
+
+I have found no simple API call to accomplish what the importer does, which
+tells me that it may not be too many people performing this particular action.
+The solution to the problem was found on \emph{Stack
+Overflow}\footnote{\url{https://stackoverflow.com/questions/12401297}}. It
+contains enough dirty details to be considered unconvenient to use, if not
+wrapping it in a class like my \type{ProjectImporter}. One would probably have
+to delve into the source code for the import wizard to find out how the import
+operation works, if no one had already done it.
+
+\section{Statistics}
+Statistics for the analysis and changes is captured by the
+\typewithref{no.uio.ifi.refaktor.aspects}{StatisticsAspect}. This an
+\emph{aspect} written in \emph{AspectJ}.
+
+\subsection{AspectJ}
+\emph{AspectJ}\footnote{\url{http://eclipse.org/aspectj/}} is an extension to
+the Java language, and facilitates combining aspect-oriented programming with
+the object-oriented programming in Java.
+
+Aspect-oriented programming is a programming paradigm that is meant to isolate
+so-called \emph{cross-cutting concerns} into their own modules. These
+cross-cutting concerns are functionalities that spans over multiple classes, but
+may not belong naturally in any of them. It can be functionality that does not
+concern the business logic of an application, and thus may be a burden when
+entangled with parts of the source code it does not really belong. Examples
+include logging, debugging, optimization and security.
+
+Aspects are interacting with other modules by defining advices. The concept of
+an \emph{advice} is known from both aspect-oriented and functional
+programming\citing{wikiAdvice2014}. It is a function that modifies another
+function when the latter is run. An advice in AspectJ is somewhat similar to a
+method in Java. It is meant to alter the behavior of other methods, and contains
+a body that is executed when it is applied.
+
+An advice can be applied at a defined \emph{pointcut}. A pointcut picks out one
+or more \emph{join points}. A join point is a well-defined point in the
+execution of a program. It can occur when calling a method defined for a
+particular class, when calling all methods with the same name,
+accessing/assigning to a particular field of a given class and so on. An advice
+can be declared to run both before, after returning from a pointcut, when there
+is thrown an exception in the pointcut or after the pointcut either returns or
+throws an exception. In addition to picking out join points, a pointcut can
+also bind variables from its context, so they can be accessed in the body of an
+advice. An example of a pointcut and an advice is found in
+\myref{lst:aspectjExample}.
+
+\begin{listing}[h]
+\begin{minted}{java}
+pointcut methodAnalyze(
+ SearchBasedExtractAndMoveMethodAnalyzer analyzer) :
+ call(* SearchBasedExtractAndMoveMethodAnalyzer.analyze())
+ && target(analyzer);
+
+after(SearchBasedExtractAndMoveMethodAnalyzer analyzer) :
+ methodAnalyze(analyzer) {
+ statistics.methodCount++;
+ debugPrintMethodAnalysisProgress(analyzer.method);
+}
+\end{minted}
+\caption{An example of a pointcut named \method{methodAnalyze},
+and an advice defined to be applied after it has occurred.}
+\label{lst:aspectjExample}
+\end{listing}
+
+\subsection{The Statistics class}
+The statistics aspect stores statistical information in an object of type
+\type{Statistics}. As of now, the aspect needs to be initialized at the point in
+time where it is desired that it starts its data gathering. At any point in time
+the statistics aspect can be queried for a snapshot of the current statistics.
+
+The \type{Statistics} class also include functionality for generating a report
+of its gathered statistics. The report can be given either as a string or it can
+be written to a file.
+
+\subsection{Advices}
+The statistics aspect contains advices for gathering statistical data from
+different parts of the benchmarking process. It captures statistics from both
+the analysis part and the execution part of the composite \ExtractAndMoveMethod
+refactoring.
+
+For the analysis part, there are advices to count the number of text selections
+analyzed and the number of methods, types, compilation units and packages
+analyzed. There are also advices that counts for how many of the methods there
+is found a selection that is a candidate for the refactoring, and for how many
+ethods there is not.
+
+There exists advices for counting both the successful and unsuccessful
+executions of all the refactorings. Both for the \ExtractMethod and \MoveMethod
+refactorings in isolation, as well as for the combination of them.
+
+\section{Optimizations}
+When looking for optimizations to make for the benchmarking process, I used the
+\emph{VisualVM}\footnote{\url{http://visualvm.java.net/}} for the Java Virtual
+Machine to both profile the application and also to make memory dumps of its
+heap.
+
+\subsection{Caching}
+When profiling the benchmark process before making any optimizations, it early
+became apparent that the parsing of source code was a place to direct attention
+towards. This discovery was done when only \emph{analyzing} source code, before
+trying to do any \emph{manipulation} of it. Caching of the parsed ASTs seemed
+like the best way to save some time, as expected. With only a simple cache of
+the most recently used AST, the analysis time was speeded up by a factor of
+around
+20. This number depends a little upon which type of system the analysis was
+run.
+
+The caching is managed by a cache manager, that now, by default, utilizes the
+not so well known feature of Java called a \emph{soft reference}. Soft
+references are best explained in the context of weak references. A \emph{weak
+reference} is a reference to an object instance that is only guaranteed to
+persist as long as there is a \emph{strong reference} or a soft reference
+referring the same object. If no such reference is found, its referred object is
+garbage collected. A strong reference is basically the same as a regular Java
+reference. A soft reference has the same guarantees as a week reference when it
+comes to its relation to strong references, but it is not necessarily garbage
+collected whenever there exists no strong references to it. A soft reference
+\emph{may} reside in memory as long as the JVM has enough free memory in the
+heap. A soft reference will therefore usually perform better than a weak
+reference when used for simple caching and similar tasks. The way to use a
+soft/weak reference is to as it for its referent. The return value then has to
+be tested to check that it is not \var{null}. For the basic usage of soft
+references, see \myref{lst:softReferenceExample}. For a more thorough
+explanation of weak references in general, see\citing{weakRef2006}.
+
+\begin{listing}[h]
+\begin{minted}{java}
+// Strong reference
+Object strongRef = new Object();
+
+// Soft reference
+SoftReference<Object> softRef =
+ new SoftReference<Object>(new Object());
+
+// Using the soft reference
+Object obj = softRef.get();
+if (obj != null) {
+ // Use object here
+}
+\end{minted}
+\caption{Showing the basic usage of soft references. Weak references is used the
+ same way. {\footnotesize (The references are part of the \code{java.lang.ref}
+package.)}}
+\label{lst:softReferenceExample}
+\end{listing}
+
+The cache based on soft references has no limit for how many ASTs it caches. It
+is generally not advisable to keep references to ASTs for prolonged periods of
+time, since they are expensive structures to hold on to. For regular plugin
+development, Eclipse recommends not creating more than one AST at a time to
+limit memory consumption. Since the benchmarking has nothing to do with user
+experience, and throughput is everything, these advices are intentionally
+ignored. This means that during the benchmarking process, the target Eclipse
+application may very well work close to its memory limit for the heap space for
+long periods during the benchmark.
+
+\subsection{Memento}
+
+\chapter{Eclipse Bugs Found}
+\todoin{Add other things and change headline?}
+
+\section{Eclipse bug 420726: Code is broken when moving a method that is
+assigning to the parameter that is also the move
+destination}\label{eclipse_bug_420726}
+This bug\footnote{\url{https://bugs.eclipse.org/bugs/show\_bug.cgi?id=420726}}
+was found when analyzing what kinds of names that was to be considered as
+\emph{unfixes} \see{unfixes}.
+
+\subsection{The bug}
+The bug emerges when trying to move a method from one class to another, and when
+the target for the move (must be a variable, local or field) is both a parameter
+variable and also is assigned to within the method body. Eclipse allows this to
+happen, although it is the sure path to a compilation error. This is because we
+would then have an assignment to a \var{this} expression, which is not allowed
+in Java.
+
+\subsection{The solution}
+The solution to this problem is to add all simple names that are assigned to in
+a method body to the set of unfixes.
+
+\section{Eclipse bug 429416: IAE when moving method from anonymous class}
+I
+discovered\footnote{\url{https://bugs.eclipse.org/bugs/show\_bug.cgi?id=429416}}
+this bug during a batch change on the \type{org.eclipse.jdt.ui} project.
+
+\subsection{The bug}
+This bug surfaces when trying to use the Move Method refactoring to move a
+method from an anonymous class to another class. This happens both for my
+simulation as well as in Eclipse, through the user interface. It only occurs
+when Eclipse analyzes the program and finds it necessary to pass an instance of
+the originating class as a parameter to the moved method. I.e. it want to pass a
+\var{this} expression. The execution ends in an
+\typewithref{java.lang}{IllegalArgumentException} in
+\typewithref{org.eclipse.jdt.core.dom}{SimpleName} and its
+\method{setIdentifier(String)} method. The simple name is attempted created in
+the method
+\methodwithref{org.eclipse.jdt.internal.corext.refactoring.structure.\\MoveInstanceMethodProcessor}{createInlinedMethodInvocation}
+so the \type{MoveInstanceMethodProcessor} was early a clear suspect.
+
+The \method{createInlinedMethodInvocation} is the method that creates a method
+invocation where the previous invocation to the method that was moved was. From
+its code it can be read that when a \var{this} expression is going to be passed
+in to the invocation, it shall be qualified with the name of the original
+method's declaring class, if the declaring class is either an anonymous clas or
+a member class. The problem with this, is that an anonymous class does not have
+a name, hence the term \emph{anonymous} class! Therefore, when its name, an
+empty string, is passed into
+\methodwithref{org.eclipse.jdt.core.dom.AST}{newSimpleName} it all ends in an
+\type{IllegalArgumentException}.
+
+\subsection{How I solved the problem}
+Since the \type{MoveInstanceMethodProcessor} is instantiated in the
+\typewithref{no.uio.ifi.refaktor.change.executors}{MoveMethod\-RefactoringExecutor},
+and only need to be a
+\typewithref{org.eclipse.ltk.core.refactoring.participants}{MoveProcessor}, I
+was able to copy the code for the original move processor and modify it so that
+it works better for me. It is now called
+\typewithref{no.uio.ifi.refaktor.refactorings.processors}{ModifiedMoveInstanceMethodProcessor}.
+The only modification done (in addition to some imports and suppression of
+warnings), is in the \method{createInlinedMethodInvocation}. When the declaring
+class of the method to move is anonymous, the \var{this} expression in the
+parameter list is not qualified with the declaring class' (empty) name.
+
+\section{Eclipse bug 429954: Extracting statement with reference to local type
+breaks code}\label{eclipse_bug_429954}
+The bug\footnote{\url{https://bugs.eclipse.org/bugs/show\_bug.cgi?id=429954}}
+was discovered when doing some changes to the way unfixes is computed.
+
+\subsection{The bug}
+The problem is that Eclipse is allowing selections that references variables of
+local types to be extracted. When this happens the code is broken, since the
+extracted method must take a parameter of a local type that is not in the
+methods scope. The problem is illustrated in
+\myref{lst:extractMethod_LocalClass}, but there in another setting.
+
+\subsection{Actions taken}
+There are no actions directly springing out of this bug, since the Extract
+Method refactoring cannot be meant to be this way. This is handled on the
+analysis stage of our Extract and Move Method refactoring. So names representing
+variables of local types is considered unfixes \see{unfixes}.
+\todoin{write more when fixing this in legal statements checker}
+
\chapter{Related Work}
\section{The compositional paradigm of refactoring}
git://git.uio.no / ifi-stolz-refaktor.git / blobdiff