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+<title>AspectJ 1.1 Readme</title>
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+<div align="right"><small>
+© Copyright 2002 Palo Alto Research Center, Incorporated,
+2003 Contributors.
+All rights reserved.
+</small></div>
+
+
+<h1>AspectJ 1.2 Readme</h1>
+
+<i> content to be replaced </i>
+
+
+<p> This is the initial release of AspectJ 1.1. It includes a small
+number of new language features as well as major improvements to the
+functionality of the tools. </p>
+
+<p>
+This document describes the differences between
+AspectJ versions 1.1 and 1.0.6.
+Users new to AspectJ need only read
+the <a href="progguide/index.html">AspectJ Programming Guide</a>
+since it describes the 1.1 language.
+Users familiar with AspectJ 1.0 may find this document
+a quicker way to learn what changed in the language
+and tools, and should use it as a guide for porting
+programs from 1.0 to 1.1.
+</p>
+
+<p>This document first summarizes changes from the 1.0 release in
+</p>
+
+<ul>
+ <li><a href="#language">the language</a>,</li>
+ <li><a href="#compiler">the compiler</a>,</li>
+ <li><a href="#tools">the support tools</a>,</li>
+ <li><a href="#runtime">the runtime</a>,</li>
+ <li><a href="#devenv">the development environment support</a>,</li>
+ <li><a href="#sources">the sources</a>, and</li>
+ <li><a href="#distribution">the distribution</a>,</li>
+</ul>
+
+<p> then <a href="#details">details</a> some of the language
+ and compiler changes,
+ and finally points readers to the bug database for any
+ <a href="#knownLimitations">known limitations</a>.
+</p>
+
+<!-- ============================== -->
+<hr>
+<h2><a name="language">The Language</a></h2>
+
+ <p> AspectJ 1.1 is a slightly different language than AspectJ 1.0.
+ In all but a few cases, programs written in AspectJ 1.0 should
+ compile correctly in AspectJ 1.1. In many cases, there are
+ new or preferred forms in AspectJ 1.1. However, some AspectJ 1.0
+ features have changed in 1.1, so some 1.0 programs
+ will not compile or will run differently in 1.1.
+ The corresponding features are marked below as compile-time
+ or run-time incompatible (<em>CTI</em> or <em>RTI</em>, respectively).
+ When the language change involves a move in the static shadow effective
+ at run-time but also apparent at compile-time (e.g., in declare
+ error or warning statements), it is marked <em>CRTI</em>.
+ Programs using run-time incompatible forms should be verified that
+ they are behaving as expected in 1.1.
+ </p>
+
+ <p>
+ Most changes to the language are additions to expressibility
+ requested by our users:
+ </p>
+
+ <ul>
+ <li><a href="#THROWS_PATTERN">Matching based on throws</a>: You can
+ now make finer discriminations between methods based on declared
+ exceptions. </li>
+
+ <li><a href="#NEW_PCDS">New kinded pointcut designators</a>: Now
+ every kind of join point has a corresponding kinded pointcut
+ designator. </li>
+ </ul>
+
+ <p> Some are have different behavior in edge cases but offer
+ improved power and clarity: </p>
+
+ <ul>
+ <li><a href="#ASPECT_PRECEDENCE">New aspect precedence form</a>:
+ AspectJ 1.1 has a new declare form, <code>declare
+ precedence</code>, that replaces the "dominates"
+ clause on aspects. (<em>CTI</em>) </li>
+
+ <li>The order of <a href="#SUPER_IFACE_INITS">initialization join
+ points for super-interfaces</a> has been clarified. (<em>RTI</em>) </li>
+ </ul>
+
+ <p> But in order to support weaving into bytecode effectively,
+ several incompatible changes had to be made to the language: </p>
+
+ <ul>
+ <li>A class's default constructor may
+ <a href="#DEFAULT_CONSTRUCTOR_CONFLICT">conflict</a> with an
+ inter-type constructor. (<em>CTI</em>) </li>
+
+ <li><a href="#NO_CALLEE_SIDE_CALL">No callee-side call join
+ points</a>: The AspectJ 1.1 compiler does not expose call join
+ points unless it is given the calling code. (<em>CRTI</em>) </li>
+
+ <li><a href="#SINGLE_INTERCLASS_TARGET">One target for intertype
+ declarations</a>. (<em>CTI</em>) </li>
+
+ <li><a href="#UNAVAILABLE_JOIN_POINTS">No initializer execution join
+ points</a>. (<em>RTI</em>)</li>
+
+ <li><a href="#AFTER_HANDLER">No after or around advice on handler
+ join points</a>. (<em>CTI</em>) </li>
+
+ <li><a href="#CONSTRUCTOR_EXECUTION_IS_BIGGER">Initializers run
+ inside constructor execution join points</a>. (<em>RTI</em>)</li>
+
+ <li><a href="#INTER_TYPE_FIELD_INITIALIZERS">inter-type field
+ initializers</a> run before class-local field initializers. (<em>RTI</em>) </li>
+
+ <li><a href="#WITHIN_MEMBER_TYPES">Small limitations of the within
+ pointcut.</a> (<em>CRTI</em>)</li>
+
+ <li><a href="#WITHIN_CODE">Small limitations of the withincode
+ pointcut.</a> (<em>CRTI</em>)</li>
+
+ <li><a href="#INSTANCEOF_ON_WILD">Can't do instanceof matching on
+ type patterns with wildcards</a>. (<em>CTI</em>) </li>
+
+ <li><a href="#NO_SOURCE_COLUMN">SourceLocation.getColumn() is
+ deprecated and will always return 0</a>. (<em>RTI</em>) </li>
+
+ <li>The interaction between aspect instantiation and advice has been
+ <a href="#ASPECT_INSTANTIATION_AND_ADVICE">clarified</a>. (<em>RTI</em>) </li>
+
+ <li><a href="#STRINGBUFFER">The String + operator is now correctly advised</a>.
+ (<em>CRTI</em>) </li>
+ </ul>
+
+ <p><a name="NEW_LIMITATIONS">There</a> are a couple of language
+ limitations for things that are rarely used that make the
+ implementation simpler, so we have restricted the language accordingly.
+ </p>
+
+ <ul>
+ <li><a href="#VOID_FIELD_SET">Field set join points now have a
+ <code>void</code> return type.</a> This will require
+ porting of code that uses the <code>set</code> PCD in conjunction
+ with after-returning or around advice. (<em>CTI</em>) <p></p></li>
+
+ <li>'declare soft: TYPE: POINTCUT;' - AspectJ 1.1 only
+ accepts TYPE rather than a TYPE_PATTERN.
+ This limitation makes declare soft
+ much easier to implement efficiently. (<em>CTI</em>) <p></p></li>
+
+ <li>Inter-type field declarations only allow a single field per
+ line, i.e. this is now illegal 'int C.field1, D.field2;' This must
+ instead be, 'int C.field1; int D.field2;' (<em>CTI</em>) <p></p></li>
+
+ <li>We did not implement the handling of more than one
+ <code>..</code> wildcard in args PCD's (rarely encountered in the
+ wild) because we didn't have the time. This might be available
+ in later releases if there is significant outcry. (<em>CTI</em>) </li>
+
+ </ul>
+
+ <p>We did not implement the long-awaited <a href="#PER_TYPE">new
+ pertype aspect specifier</a> in this release, but it may well
+ be in a future release.</p>
+
+
+<!-- ============================== -->
+<hr>
+<h2><a name="compiler">The Compiler</a></h2>
+
+ <p> The compiler for AspectJ 1.1 is different than the compiler for
+ AspectJ 1.0. While this document describes the differences in the
+ compiler, it's worthwhile noting that much effort has been made to
+ make sure that the interface to ajc 1.1 is, as much as possible, the
+ same as the interface to ajc 1.0. There are two important changes
+ under the hood, however. </p>
+
+ <p> First, the 1.1 compiler is implemented on top of the
+ open-source Eclipse compiler. This has two benefits: It allows us
+ to concentrate on the AspectJ extensions to Java and let the Eclipse
+ team worry about making sure the Java edge cases work, and it allows
+ us to piggyback on Eclipse's already mature incremental compilation
+ facilities. </p>
+
+ <p> Second, ajc now cleanly delineates compilation of source code
+ from assembly (or "weaving") of bytecode. The compiler still
+ accepts source code, but internally it transforms it into bytecode
+ format before weaving. </p>
+
+ <p> This new architecture, and other changes to the compiler, allows
+ us to implement some features that were defined in the AspectJ 1.0
+ language but not implementable in the 1.1 compiler. It also makes
+ some new features available: </p>
+
+ <ul>
+ <li><a href="#SOURCEROOT">The -sourceroots option</a>
+ takes one or more directories, and indicates that all the source
+ files in those directories should be passed to the compiler. </li>
+
+ <li><a href="#BYTECODE_WEAVING">The -injars option</a>
+ takes one or more jar files, and indicates that all the classfiles
+ in the jar files should be woven into. </li>
+
+ <li><a href="#BINARY_ASPECTS">The -aspectpath option</a>
+ takes one or more jar files, and weaves any aspects in .class form
+ into the sources.</li>
+
+ <li><a href="#OUTJAR">The -outjar option</a> indicates
+ that the result classfiles of compiling and weaving should be placed
+ in the specified jar file. </li>
+
+ <li><a href="#XLINT">The -Xlint option</a> allows control over
+ warnings.</li>
+
+ <li><a href="#OTHER_X_OPTIONS">Various -X options</a> changed.</li>
+
+ <li><a href="#INCREMENTAL">The -incremental option</a> tells the
+ AspectJ 1.1 compiler to recompile only as necessary. </li>
+ </ul>
+
+ <p> Some other features we wanted to support for 1.1, but did not make
+ it into this release: </p>
+
+ <ul>
+ <li><a href="#ERROR_MESSAGES">Error messages will sometimes be scary</a></li>
+ <li><a href="#MESSAGE_CONTEXT">Source code context is not shown
+ for errors and warnings detected during bytecode weaving</a></li>
+ </ul>
+
+ <p> But some features of the 1.0 compiler are not supported in the
+ 1.1 compiler: </p>
+
+ <ul>
+ <li><a href="#NO_SOURCE">The source-related options</a> -preprocess,
+ -usejavac, -nocomment and -workingdir</li>
+
+ <li><a href="#NO_STRICT_LENIENT">The -strict and -lenient options</a>
+ </li>
+
+ <li><a href="#NO_PORTING">The -porting option</a></li>
+
+ <li><a href="#13_REQUIRED">J2SE 1.2 is not supported;
+ J2SE 1.3 or later is required.</a></li>
+ </ul>
+
+ <p> A short description of the options ajc accepts is available with
+ "<code>ajc -help</code>".
+ Longer descriptions are available in the
+ <a href="devguide/ajc-ref.html">Development Environment Guide
+ section on ajc</a>. </p>
+ <p> </p>
+
+
+ <p> Some changes to the implementation are almost entirely
+ internal:
+ </p>
+
+ <ul>
+ <li>The behavior of the compiler in
+ <a href="#TARGET_TYPES_MADE_PUBLIC">lifting the visibility</a> of
+ the target types of some declares and pointcuts to public has been
+ clarified. </li>
+ </ul>
+
+ <p> Also, it is worth noting that because AspectJ now works on bytecode,
+ it is somewhat sensitive to how different compilers generate
+ bytecode, especially when compiling with and without <a
+ href="#ONE_FOUR_METHOD_SIGNATURES">the -1.4 flag</a>. </p>
+
+
+
+<!-- ============================== -->
+<hr>
+<h2><a name="tools">Support Tools</a></h2>
+
+ <p>This release includes an Ant task for old-style 1.0 build
+ scripts, a new task for all the new compiler options, and a
+ CompilerAdapter to support running <code>ajc</code> with the Javac
+ task by setting the <code>build.compiler</code> property.
+ The new task can automatically copy input resources to output
+ and work in incremental mode using a "tag" file.
+ </p>
+
+ <p>This release does not include <code>ajdoc</code>, the
+ documentation tool for AspectJ sources.
+ Ajdoc is deeply dependent on the
+ abstract syntax tree classes from the old compiler, so it needs a
+ bottom-up rewrite. We think it best to use this opportunity to
+ implement more general API's for publishing and rendering static
+ structure. Because those API's are last to settle in the new
+ architecture, and because the compiler itself is a higher priority,
+ we are delaying work on ajdoc until after the 1.1 release.</p>
+
+ <p>AspectJ 1.1 will not include <tt>ajdb</tt>, the AspectJ
+ stand-alone debugger. It is no longer necessary for two reasons.
+ First, the -XnoInline flag will tell the compiler to generate
+ code without inlining that should work correctly with any Java
+ debugger. For code generated with inlining enabled, more
+ third-party debuggers are starting to work according to JSR 45,
+ "Debugging support for other languages," which is supported by
+ AspectJ 1.0. We aim to support JSR-45 in AspectJ 1.1, but
+ support will not be in the initial release. Consider using
+ the -XnoInline flag until support is available.</p>
+
+<!-- ============================== -->
+<hr>
+<h2><a name="runtime">The Runtime Library</a></h2>
+
+ <p>This release has minor additions to the runtime library classes.
+ As with any release, you should compile and run with the runtime
+ library that came with your compiler, and you may run with
+ a later version of the library without recompiling your code.</p>
+
+ <p> In one instance, however, runtime classes behave differently this release.
+ Because the AspectJ 1.1 compiler does its weaving through
+ bytecode, column numbers of source locations are not available.
+ Therefore, <code>thisJoinPoint.getSourceLocation().getColumn()</code>
+ is deprecated and will always return 0. </p>
+
+<!-- ============================== -->
+<hr>
+<h2><a name="devenv">The AJDE Tools</a></h2>
+
+ <p> The AspectJ Browser supports incremental compilation and running
+ programs. AJDE for JBuilder, AJDE for NetBeans, and AJDE for Emacs
+are now independent SourceForge projects (to keep their licenses).
+ They use the batch-build mode of the new compiler.
+ </p>
+
+<!-- ============================== -->
+<hr>
+<h2><a name="sources">The Sources and the Licenses</a></h2>
+
+ <p> The AspectJ tools sources are available under the
+ <a href="http://eclipse.org/legal/cpl-v10.html">Common Public
+ License</a> in the CVS repository
+ at <a href="http://eclipse.org/aspectj">http://eclipse.org/aspectj</a>.
+ For more information, see the FAQ entry on
+ <a href="faq.html#q:buildingsource">building sources</a>.
+ </p>
+
+
+<!-- ============================== -->
+<hr>
+<h2><a name="distribution">The AspectJ distribution</a></h2>
+
+ <p> AspectJ 1.0 had many distributions - for the tools,
+ the documentation, each IDE support package,
+ their respective sources, and the Ant tasks -
+ because they came under different licenses.
+ All of AspectJ 1.1 is licensed under the CPL 1.0,
+ so the tools, Ant tasks, and documentation are all
+ in one distribution available from
+ <a href="http://eclipse.org/aspectj">
+ http://eclipse.org/aspectj</a>.
+To retain their MPL 1.1 license,
+Ajde for
+<a href="http://aspectj4emacs.sourceforge.net/">Emacs</a>,
+<a href="http://aspectj4netbean.sourceforge.net/">NetBeans</a> and
+<a href="http://aspectj4jbuildr.sourceforge.net/">JBuilder</a>
+are now independent SourceForge projects. </p>
+
+ </p>
+
+
+<!-- ============================== -->
+<hr>
+<hr>
+<h2><a name="details">Details</a> of some language and compiler changes</h2>
+
+ <h3><a name="ASPECT_INSTANTIATION_AND_ADVICE">Aspect Instantiation
+ and Advice</a></h3>
+
+ <p> In AspectJ 1.0.6, we made an effort to hide some complications
+ with Aspect instantiation from the user. In particular, the
+ following code compiled and ran:
+ </p>
+
+ <PRE>
+ public class Client
+ {
+ public static void main(String[] args) {
+ Client c = new Client();
+ }
+ }
+
+ aspect Watchcall {
+ pointcut myConstructor(): execution(new(..));
+
+ before(): myConstructor() {
+ System.err.println("Entering Constructor");
+ }
+ }
+ </PRE>
+
+ <p> But there's a conceptual problem with this code: The before
+ advice should run before the execution of all constructors in the
+ system. It must run in the context of an instance of the
+ Watchcall aspect. The only way to get such an instance is to have
+ Watchcall's default constructor execute. But before that
+ executes, we need to run the before advice...</p>
+
+ <p> AspectJ 1.0.6 hid this circularity through the ad-hoc
+ mechanism of preventing an aspect's advice from matching join
+ points that were within the aspect's definition, and occurred
+ before the aspect was initialized. But even in AspectJ 1.0.6,
+ this circularity could be exposed:
+ </p>
+
+ <PRE>
+ public class Client
+ {
+ public static int foo() { return 3; }
+ public static void main(String[] args) {
+ Client c = new Client();
+ }
+ }
+
+ aspect Watchcall {
+ int i = Client.foo();
+ pointcut myConstructor():
+ execution(new(..)) || execution(int foo());
+
+ before(): myConstructor() {
+ System.err.println("Entering Constructor");
+ }
+ }
+ </PRE>
+
+ <p>This program would throw a NullPointerException when run, since
+ Client.foo() was called before the Watchcall instance could be
+ instantiated. </p>
+
+ <p> In AspectJ 1.1, we have decided that half-hiding the problem
+ just leads to trouble, and so we are no longer silently hiding
+ some join points before aspect initialization. However, we have
+ provided a better exception than a NullPointerException for this
+ case. In AspectJ 1.1, both of the above programs will throw
+ org.aspectj.lang.NoAspectBoundException.
+ </p>
+
+ <h3><a name="THROWS_PATTERN">Matching based on throws</a></h3>
+
+ <p> Type patterns may now be used to pick out methods and
+ constructors based on their throws clauses. This allows the
+ following two kinds of extremely wildcarded pointcuts: </p>
+
+ <pre> pointcut throwsMathlike():
+ // each call to a method with a throws clause containing at least
+ // one exception with "Math" in its name.
+ call(* *(..) throws *..*Math*);
+
+ pointcut doesNotThrowMathlike():
+ // each call to a method with a throws clause containing no
+ // exceptions with "Math" in its name.
+ call(* *(..) throws !*..*Math*);
+ </pre>
+
+ <p> The longwinded rules are that a method or constructor pattern
+ can have a "throws clause pattern". Throws clause patterns look
+ like: </p>
+
+ <pre> ThrowsClausePattern:
+ ThrowsClausePatternItem ("," ThrowsClausePatternItem)*
+
+ ThrowsClausePatternItem:
+ ["!"] TypeNamePattern
+ </pre>
+
+ <p> A ThrowsClausePattern matches the ThrowsClause of any code
+ member signature. To match, each ThrowsClausePatternItem must
+ match the throws clause of the member in question. If any item
+ doesn't match, then the whole pattern doesn't match. This rule is
+ unchanged from AspectJ 1.0. </p>
+
+ <p> If a ThrowsClausePatternItem begins with "!", then it matches
+ a particular throws clause if and only if <em>none</em> of the
+ types named in the throws clause is matched by the
+ TypeNamePattern. </p>
+
+ <p> If a ThrowsClausePatternItem does not begin with "!", then it
+ matches a throws clause if and only if <em>any</em> of the types
+ named in the throws clause is matched by the TypeNamePattern.</p>
+
+ <p> These rules are completely backwards compatible with
+ AspectJ 1.0. The rule for "!" matching has one potentially
+ surprising property, in that the two PCD's shown below will have
+ different matching rules. </p>
+
+ <pre> [1] call(* *(..) throws !IOException)
+ [2] call(* *(..) throws (!IOException))
+
+ void m() throws RuntimeException, IOException {}
+ </pre>
+
+ <p> [1] will NOT match the method m(), because method m's throws
+ clause declares that it throws IOException. [2] WILL match the
+ method m(), because method m's throws clause declares the it
+ throws some exception which does not match IOException,
+ i.e. RuntimeException. </p>
+
+ <h3><a name="NEW_PCDS">New kinded pointcut designators</a></h3>
+
+ <p> AspectJ 1.0 does not provide kinded pointcut designators for
+ two (rarely used) join points: preinitialization (the code that
+ runs before a super constructor call is made) and advice
+ execution. AspectJ 1.1 does not change the meaning of the join
+ points, but provides two new pointcut designators to pick out
+ these join points, thus making join points and pointcut
+ designators more parallel. </p>
+
+ <p> <code>adviceexectuion()</code> will pick out advice execution
+ join points. You will usually want to use <code>adviceexecution()
+ && within(Aspect)</code> to restrict it to only those pieces of
+ advice defined in a particular aspect. <br>
+ <code>preinitialization(<var>ConstructorPattern</var>)</code> will
+ pick out pre-initialization join points where the initialization
+ process is entered through
+ <code><var>ConstructorPattern</var></code>. </p>
+
+ <h3><a name="PER_TYPE">New pertype aspect specifier</a> (not in 1.1)</h3>
+
+ <p>We strongly considered adding a pertype aspect kind to 1.1.
+ This is somewhat motivated by the new
+ <a href="#SINGLE_INTERCLASS_TARGET">restrictions on inter-type
+ declarations<a>. This is also motivated by many previous request
+ to support a common logging idiom. Here's what pertype would look
+ like:</p>
+
+ <pre> /** One instance of this aspect will be created for each class,
+ * interface or aspect in the com.bigboxco packages.
+ */
+ aspect Logger pertype(com.bigboxco..*) {
+ /* This field holds a logger for the class. */
+ Log log;
+
+ /* This advice will run for every public execution defined by
+ * a type for which a Logger aspect has been created, i.e.
+ * any type in com.bigboxco..*
+ */
+ before(): execution(public * *(..)) {
+ log.enterMethod(thisJoinPoint.getSignature().getName());
+ }
+
+ /* We can use a special constructor to initialize the log field */
+ public Logger(Class myType) {
+ this.log = new Log(myType);
+ }
+ }
+
+ /** External code could use aspectOf to get at the log, i.e. */
+ Log l = Logger.aspectOf(com.bigboxco.Foo.class).log;
+ </pre>
+
+ <p>The one open question that we see is how this should interact
+ with inner types. If a pertype aspect is created for an outer
+ type should advice in that aspect run for join points in inner
+ types? That is the behavior of the most common uses of this
+ idiom. </p>
+
+ <p> In any case, this feature will not be in AspectJ 1.1.
+ </p>
+
+ <h3><a name="SINGLE_INTERCLASS_TARGET">One target for intertype
+ declarations</a></h3>
+
+ <p> Intertype declarations (once called "introductions") in
+ AspectJ 1.1 can only have one target type. So the following code
+ intended to declare that there is a void doStuff() method on all
+ subtypes of Target is not legal AspectJ 1.1 code.
+ </p>
+
+ <pre> aspect A {
+ public void Target+.doStuff() { ... }
+ }
+ </pre>
+
+ <p> The functionality of "multi-intertype declarations" can be
+ recovered by using a helper interface.
+ </p>
+
+ <pre> aspect A {
+ private interface MyTarget {}
+ declare parents: Target+ implements MyTarget;
+ public void MyTarget.doStuff() { ... }
+ }
+ </pre>
+
+ <p> We believe this is better style in AspectJ 1.0 as well, as it
+ makes clear the static type of "this" inside the method body.
+ </p>
+
+ <p> The one piece of functionality that can not be easily
+ recovered is the ability to add static fields to many classes. We
+ believe that the <a href="#PER_TYPE">pertype proposal</a> provides
+ this functionality in a much more usable form.</p>
+
+ <h3><a name="UNAVAILABLE_JOIN_POINTS">No initializer execution join
+ points</a></h3>
+
+ <p> AspectJ 1.1 does not consider initializer execution a
+ principled join point. The collection of initializer code (the
+ code that sets fields with initializers and the code in non-static
+ initializer blocks) is something that makes sense only in Java
+ source code, not in Java bytecode. </p>
+
+ <h3><a name="AFTER_HANDLER"></a>No after or around advice on handler
+ join points</h3>
+
+ <p> The end of an exception handler is underdetermined in bytecode,
+ so ajc will not implement after or around advice on handler join
+ points, instead signaling a compile-time error.</p>
+
+ <h3><a name="CONSTRUCTOR_EXECUTION_IS_BIGGER">Initializers run
+ inside constructor execution join points</a></h3>
+
+ <p> The code generated by the initializers in Java source code now
+ runs inside of constructor execution join points. This changes
+ how before advice runs on constructor execution join points.
+ Consider: </p>
+
+ <pre> class C {
+ C() { }
+ String id = "identifier"; // this assignment
+ // has to happen sometime
+ }
+ aspect A {
+ before(C c) this(c) && execution(C.new()) {
+ System.out.println(c.id.length());
+ }
+ }
+ </pre>
+
+ <p> In AspectJ 1.0, this will print "10", since id is assigned its
+ initial value prior to the before advice's execution. However, in
+ AspectJ 1.1, this will throw a NullPointerExcception, since "id"
+ does not have a value prior to the before advice's execution.
+ </p>
+
+ <p> Note that the various flavors of after returning advice are
+ unchanged in this respect in AspectJ 1.1. Also note that this
+ only matters for the execution of constructors that call a
+ super-constructor. Execution of constructors that call a
+ this-constructor are the same in AspectJ 1.1 as in AspectJ 1.0.
+ </p>
+
+ <p> We believe this difference should be minimal to real programs,
+ since programmers using before advice on constructor execution
+ must always assume incomplete object initialization, since the
+ constructor has not yet run. </p>
+
+ <h3><a name="INTER_TYPE_FIELD_INITIALIZERS">Inter-type field initializers</a></h3>
+
+ <p> The initializer, if any, of an inter-type field definition runs
+ before the class-local initializers of its target class. </p>
+
+ <p> In AspectJ 1.0.6, such an initializer would run after the
+ initializers of a class but before the execution of any of its
+ constructor bodies. As already discussed in the sections about
+ <a href="#UNAVAILABLE_JOIN_POINTS">initializer execution join
+ points</a> and <a href="#CONSTRUCTOR_EXECUTION_IS_BIGGER">constructor
+ execution</a>, the point in code between the initializers of a class
+ and its constructor body is not principled in bytecode. So we had a
+ choice of running the initializer of an inter-type field definition at
+ the beginning of initialization (i.e., before initializers from
+ the target class) or at the end (i.e., just before its called
+ constructor exits). We chose the former, having this pattern in mind:
+ </p>
+
+ <PRE>
+ int C.methodCount = 0;
+ before(C c): this(c) && execution(* *(..)) { c.methodCount++; }
+ </PRE>
+
+ <p> We felt there would be too much surprise if a constructor called a
+ method (thus incrementing the method count) and then the field was
+ reset to zero after the constructor was done.
+ </p>
+
+ <h3><a name="WITHIN_MEMBER_TYPES">Small limitations of the within
+ pointcut</a></h3>
+
+ <p>Because of the guarantees made (and not made) by the Java
+ classfile format, there are cases where AspectJ 1.1 cannot
+ guarantee that the within pointcut designator will pick out all
+ code that was originally within the source code of a certain
+ type.
+ </p>
+
+ <p> The non-guarantee applies to code inside of anonymous and
+ local types inside member types. While the within pointcut
+ designator behaves exactly as it did in AspectJ 1.0 when given a
+ package-level type (like C, below), if given a member-type (like
+ C.InsideC, below), it is not guaranteed to capture code in
+ contained local and anonymous types. For example: </p>
+
+ <pre> class C {
+ Thread t;
+ class InsideC {
+ void setupOuterThread() {
+ t = new Thread(
+ new Runnable() {
+ public void run() {
+ // join points with code here
+ // might not be captured by
+ // within(C.InsideC), but are
+ // captured by within(C)
+ System.out.println("hi");
+ }
+ });
+ }
+ }
+ }
+ </pre>
+
+ <p> We believe the non-guarantee is small, and we haven't verified
+ that it is a problem in practice. </p>
+
+ <h3><a name="WITHIN_CODE">Small limitations of the withincode
+ pointcut</a></h3>
+
+ <p>The withincode pointcut has similar issues to those described
+ above for within.
+ </p>
+
+ <h3><a name="INSTANCEOF_ON_WILD">Can't do instanceof matching on
+ type patterns with wildcard</a></h3>
+
+ <p>The pointcut designators this, target and args specify a
+ dynamic test on their argument. These tests can not be performed
+ on type patterns with wildcards in them. The following code that
+ compiled under 1.0 will be an error in AspectJ-1.1:</p>
+
+ <pre> pointcut oneOfMine(): this(com.bigboxco..*);
+ </pre>
+
+ <p>The only way to implement this kind of matching in a modular
+ way would be to use the reflection API at runtime on the Class of
+ the object. This would have a very high performance cost and
+ possible security issues. There are two good work-arounds. If
+ you control the source or bytecode to the type you want to match
+ then you can use declare parents, i.e.:</p>
+
+ <pre> private interface OneOfMine {}
+ declare parents: com.bigboxco..* implements OneOfMine;
+ pointcut oneOfMine(): this(OneOfMine);
+ </pre>
+
+ <p>If you want the more dynamic matching and are willing to pay
+ for the performance, then you should use the Java reflection API
+ combined with if. That would look something like:</p>
+
+ <pre> pointcut oneOfMine(): this(Object) &&
+ if(classMatches("com.bigboxco..*",
+ thisJoinPoint.getTarget().getClass()));
+
+ static boolean classMatches(String pattern, Class _class) {
+ if (patternMatches(pattern, _class.getName())) return true;
+ ...
+ }
+ </pre>
+
+ <p>Note: wildcard type matching still works in all other PCD's that
+ match based on static types. So, you can use
+ 'within(com.bigboxco..*+)' to match any code lexically within one
+ of your classes or a subtype thereof. This is often a good
+ choice.</p>
+ </p>
+
+
+ <h3><a name="NO_SOURCE_COLUMN">SourceLocation.getColumn()</a></h3>
+
+ <p>The Java .class file format contains information about the
+ source file and line numbers of its contents; however, it has no
+ information about source columns. As a result, we can not
+ effectively support the access of column information in the
+ reflection API. So, any calls to
+ thisJoinPoint.getSourceLocation().getColumn() will be marked as
+ deprecated by the compiler, and will always return 0.</p>
+
+ <h3><a name="ASPECT_PRECEDENCE">Aspect precedence</a></h3>
+
+ <p> AspectJ 1.1 has a new declare form:
+ </p>
+
+ <pre> declare precedence ":" TypePatternList ";"
+ </pre>
+
+ <p> This is used to declare advice ordering constraints on join
+ points. For example, the constraints that (1) aspects that have
+ Security as part of their name should dominate all other aspects, and
+ (2) the Logging aspect (and any aspect that extends it) should
+ dominate all non-security aspects, can be expressed by: </p>
+
+ <pre> declare precedence: *..*Security*, Logging+, *;
+ </pre>
+
+ <p> In the TypePatternList, the wildcard * means "any type not matched
+ by another type in the declare precedence". </p>
+
+ <h4>Various cycles</h4>
+
+ <p> It is an error for any aspect to be matched by more than one
+ TypePattern in a single declare precedence, so: </p>
+
+ <pre> declare precedence: A, B, A ; // error
+ </pre>
+
+ <p> However, multiple declare precedence forms may legally have this
+ kind of circularity. For example, each of these declare precedence is
+ perfectly legal:
+ </p>
+
+ <pre> declare precedence: B, A;
+ declare precedence: A, B;
+ </pre>
+
+ <p> And a system in which both constraints are active may also be
+ legal, so long as advice from A and B don't share a join point. So
+ this is an idiom that can be used to enforce that A and B are strongly
+ independent. </p>
+
+ <h4>Applies to concrete aspects</h4>
+
+ <p> Consider the following library aspects:
+ </p>
+
+ <pre> abstract aspect Logging {
+ abstract pointcut logged();
+
+ before(): logged() {
+ System.err.println("thisJoinPoint: " + thisJoinPoint);
+ }
+ }
+
+ aspect MyProfiling {
+ abstract pointcut profiled();
+
+ Object around(): profiled() {
+ long beforeTime = System.currentTimeMillis();
+ try {
+ return proceed();
+ } finally {
+ long afterTime = System.currentTimeMillis();
+ addToProfile(thisJoinPointStaticPart,
+ afterTime - beforeTime);
+ }
+ }
+ abstract void addToProfile(
+ org.aspectj.JoinPoint.StaticPart jp,
+ long elapsed);
+ }
+ </pre>
+
+ <p> In order to use either aspect, they must be extended with
+ concrete aspects, say, MyLogging and MyProfiling. In AspectJ
+ 1.0, it was not possible to express that Logging's advice (when
+ concerned with the concrete aspect MyLogging) dominated
+ Profiling's advice (when concerned with the concrete aspect
+ MyProfiling) without adding a dominates clause to Logging
+ itself. In AspectJ 1.1, we can express that constraint with a
+ simple: </p>
+
+ <pre> declare precedence: MyLogging, MyProfiling;
+ </pre>
+
+ <h4>Changing order of advice for sub-aspects</h4>
+
+ <p> By default, advice in a sub-aspect has more precedence than
+ advice in a super-aspect. One use of the AspectJ 1.0 dominates
+ form was to change this precedence:
+ </p>
+
+ <pre> abstract aspect SuperA dominates SubA {
+ pointcut foo(): ... ;
+
+ before(): foo() {
+ // in AspectJ 1.0, runs before the advice in SubA
+ // because of the dominates clause
+ }
+ }
+
+ aspect SubA extends SuperA {
+ before(): foo() {
+ // in AspectJ 1.0, runs after the advice in SuperA
+ // because of the dominates clause
+ }
+ }
+ </pre>
+
+ <p> This no longer works in AspectJ 1.1, since declare precedence only
+ matters for concrete aspects. Thus, if you want to regain this kind
+ of precedence change, you will need to refactor your aspects.
+ </p>
+
+ <h3><a name="SOURCEROOT">The -sourceroots option</a></h3>
+
+ <p> The AspectJ 1.1 compiler now accepts a -sourceroots option used to
+ pass all .java files in particular directories to the compiler. It
+ takes either a single directory name, or a list of directory names
+ separated with the CLASSPATH separator character (":" for various
+ Unices, ";" for various Windows). </p>
+
+ <p> So, if you have your project separated into a gui module and a
+ base module, each of which is stored in a directory tree, you might
+ use one of
+ </p>
+
+ <pre> ajc -sourceroots /myProject/gui:/myProject/base
+ ajc -sourceroots d:\myProject\gui;d:\myProject\base
+ </pre>
+
+ <p> This option may be used in conjunction with lst files, listing
+ .java files on the command line, and the -injars option.
+ </p>
+
+ <h3><a name="BYTECODE_WEAVING">The -injars option</a></h3>
+
+ <p> The AspectJ 1.1 compiler now accepts an -injars option used to
+ pass all .class files in a particular jar file to the compiler. It
+ takes either a single directory name, or a list of directory names
+ separated with the CLASSPATH separator character (":" for various
+ Unices, ";" for various Windows). </p>
+
+ <p> So, if MyTracing.java defines a trace aspect that you want to
+ apply to all the classes in myBase.jar and myGui.jar, you would use
+ one of: </p>
+
+ <pre> ajc -injars /bin/myBase.jar:/bin/myGui.jar MyTracing.java
+ ajc -injars d:\bin\myBase.jar;d:\bin\myGui.jar MyTracing.java
+ </pre>
+
+ <p> The class files in the input jars must not have had advice woven
+ into them, since AspectJ enforces the requirement that advice is woven
+ into a particular classfile only once. So if the classfiles in the
+ jar file are to be created with the ajc compiler (as opposed to a pure
+ Java compiler), they should not be compiled with any non-abstract
+ aspects. </p>
+
+ <p> This option may be used in conjunction with lst files, listing
+ .java files on the command line, and the -sourceroots option.
+ </p>
+
+ <h3><a name="OUTJAR">The -outjar option</a></h3>
+
+ <p> The -outjar option takes the name of a jar file into which the
+ results of the compilation should be put. For example:
+
+ <pre> ajc -injars myBase.jar MyTracing.java -outjar myTracedBase.jar
+ </pre>
+
+ <p> No meta information is placed in the output jar file. </p>
+
+ <h3><a name="INCREMENTAL">Incremental compilation</a></h3>
+
+ <p> The AspectJ 1.1 compiler now supports incremental compilation.
+ When ajc is called with the -incremental option, it must also be
+ passed a -sourceroots option specifying a directory to incrementally
+ compile. Once the initial compile is done, ajc waits for console
+ input. Every time it reads a new line (i.e., every time the user
+ hits return) ajc recompiles those input files that need recompiling.
+ </p>
+
+ <h4>Limitations</h4>
+
+ <p> This new functionality is still only lightly tested. </p>
+
+ <h3><a name="XNOWEAVE">-XnoWeave, a compiler option to suppress
+ weaving</a></h3>
+
+ <p> The -XnoWeave option suppresses weaving, and generates
+ classfiles and that can be passed to ajc again (through the
+ -injars option) to generate final, woven classfiles. </p>
+
+ <p> This option was originally envisioned to be the primary way to
+ generate binary aspects that could be linked with other code, and
+ so it was previously (in AspectJ 1.1beta1) named
+ <code>-noweave</code>. We feel that using the
+ <code><a href="#BINARY_ASPECTS">-aspectpath</a></code> option is a
+ much better option. There may still be use cases for unwoven
+ classfiles, but we've moved the flag to experimental status.
+ </p>
+
+ <h3><a name="BINARY_ASPECTS">-aspectpath, working with aspects in .class/.jar
+ form</a> </h3>
+
+ <p> When aspects are compiled into classfiles, they include all
+ information necessary for the ajc compiler to weave their advice
+ and deal with their inter-type declarations. In order for these
+ aspects to have an effect on a compilation process, they must be
+ passed to the compiler on the -aspectpath. Every .jar file on
+ this path will be searched for aspects and any aspects that are
+ found will be enabled during the compilation. The binary forms of
+ this aspects will be untouched. </p>
+
+ <h3><a name="NO_CALLEE_SIDE_CALL">Callee-side call join
+ points</a></h3>
+
+ <p> The 1.0 implementation of AspectJ, when given:
+ </p>
+
+ <pre> class MyRunnable implements Runnable {
+ public void run() { ... }
+ }
+
+ aspect A {
+ call(): (void run()) && target(MyRunnable) {
+ // do something here
+ }
+ }
+ </pre>
+
+ <p> would cause A's advice to execute even when, say, java.lang.Thread
+ called run() on a MyRunnable instance.
+ </p>
+
+ <p> With the new compiler, two things have happened in regard to
+ callee-side calls:
+ </p>
+
+ <ol>
+ <li>because the programmer has access to more code (i.e.,
+ bytecode, not just source code), callee-side calls are much
+ less important to have.</li>
+
+ <li>because compilation is more modular, allowing and
+ encouraging separate compilation, callee-side calls are much
+ more difficult to implement</li>
+ </ol>
+
+ <p> With these two points in mind, advice in an aspect will not be
+ applied to call join points whose call site is completely
+ unavailable to the aspect. </p>
+
+ <ol>
+ <li>One reason (though not the only reason) we worked so hard in
+ the <em>implementation</em> of 1.0.6 to expose call join
+ points, even if we only had access to the callee's code, was
+ that otherwise users couldn't get access to call join points
+ where the call was made from bytecode. This is no longer the
+ case. In short, the implementation controls much more code (or
+ has the capability to) than ever before.</li>
+
+ <li>The implementation model for the AspectJ 1.1 compiler is to
+ separate the compilation of aspects/advice from their
+ weaving/linking. A property of the model is that the
+ compilation requires no access to "target" code, only the
+ weaving/linking does, and weaving/linking is inherently
+ per-class local: No action at weaving/linking time depends on
+ the coordinated mangling of multiple classfiles. Rather, all
+ weaving is done on a per classfile basis. This is an essential
+ property for the current separate compilation model. <br>
+
+ However, allowing implementation of call advice on either
+ side requires simultaneous knowledge of both sides. If we first
+ have access to a call, we can't decide to simply put the advice
+ on the call site, since later we may decide to implement on the
+ callee.</li>
+ </ol>
+
+ <p>This implementation decision is completely in the letter and
+ the spirit of the AspectJ language. From the semantics guide
+ describing code the implementation controls:</p>
+
+ <blockquote>
+ But AspectJ implementations are permitted to deviate from this
+ in a well-defined way -- they are permitted to advise only
+ accesses in <em>code the implementation
+ controls</em>. Each implementation is free within certain
+ bounds to provide its own definition of what it means to control
+ code.
+ </blockquote>
+
+ <p>And about a particular decision about the 1.0.6
+ implementation:</p>
+
+ <blockquote>
+ Different join points have different requirements. Method call
+ join points can be advised only if ajc controls
+ <em>either</em> the code for the caller or the code
+ for the receiver, and some call pointcut designators may
+ require caller context (what the static type of the receiver
+ is, for example) to pick out join points.
+ </blockquote>
+
+ <p> The 1.1 implementation makes a different design decision:
+ Method call join points can be advised only if ajc (in compiler or
+ linker form) controls the code for the caller. </p>
+
+ <p>What does 1.1 gain from this?</p>
+
+ <ul>
+ <li>a clear (and implemented) separate compilation model (see
+ point 2, above)</li>
+
+ <li>a less confusing interaction between call join points and
+ the thisJoinPoint reflective object: We still get bug reports
+ about source information sometimes existing and sometimes not
+ existing at call join points.</li>
+ </ul>
+
+ <p> What does 1.1 lose from this?</p>
+
+ <ul>
+ <li>The ability to capture all calls to Runnable.run() from
+ anywhere to code ajc has access too, even from Thread, even if
+ you don't compile java.lang with ajc.</li>
+
+ <li>The ability to, without access to the caller, capture entry to
+ a particular method, but not super calls.</li>
+
+ <li>A code-size-improvement performance optimization.</li>
+ </ul>
+
+ <p> What are the possibilities for the future?</p>
+
+ <ul>
+ <li>AspectJ 1.1.1 could expand its capture of call join points,
+ possibly at the expense of separate compilation clarity,
+ possibly not. </li>
+
+ <li>AspectJ 1.1.1 could re-introduce reception join points from
+ AspectJ 0.7 (what callee-side call join points actually are):
+ though they would never ever be taught in a tutorial or
+ entry-level description of the model, they may have specialized
+ uses.</li>
+ </ul>
+
+ <p> How will this affect developers?</p>
+ <ul>
+ <li>When using the call PCD but only supplying the callee
+ code, supply the calling code or use the execution PCD instead.
+ </li>
+ </ul>
+
+ <h3><a name="OTHER_X_OPTIONS">Various -X options</a></h3>
+
+ <p> The AspectJ 1.0 compiler supported a number of options that
+ started with X, for "experimental". Some of them will not be
+ supported in 1.1, either because the "experiment" succeeded (in
+ which case it's part of the normal functionality) or failed.
+ Others will be supported as is (or nearly so) in 1.1:
+ </p>
+
+ <ul>
+ <li>-XOcodeSize: This is no longer necessary because inlining
+ of around advice is on by default. We support its inverse,
+ <a href="#XNOINLINE"><code>-XnoInline</code></a>.
+ </li>
+
+ <li><a href="#XNOWEAVE">-XnoWeave, a compiler option to suppress
+ weaving</a></li>
+
+ <li>-XtargetNearSource: Not supported in this release. </li>
+
+ <li>-XserializableAspects: Supported. </li>
+
+ <li>-XaddSafePrefix: This option will not be supported in 1.1 at
+ all because we're now always using (what we believe to be) safe
+ prefixes. </li>
+
+ <li>-Xlint: Still supported, with <a href="#XLINT">various
+ options</a>. </li>
+ </ul>
+
+ <h3><a name="ERROR_MESSAGES">Some confusing error messages</a></h3>
+
+ <p>Building on the eclipse compiler has given us access to a very
+ sophisticated problem reporting system as well as highly optimized
+ error messages for pure Java code. Often this leads to noticeably
+ better error messages than from ajc-1.0.6. However, when we don't
+ handle errors correctly this can sometimes lead to cascading error
+ messages where a single small syntax error will produce dozens of
+ other messages. Please report any very confusing error messages as
+ bugs.</p>
+
+
+ <h3><a name="MESSAGE_CONTEXT">Source code context is not shown
+ for errors and warnings detected during bytecode weaving</a></h3>
+
+ <p>For compiler errors and warnings detected during bytecode weaving,
+ source code context will not be displayed. In particular, for declare
+ error and declare warning statements, the compiler now only emits the
+ file and line. We are investigating ways to overcome this in cases
+ where the source code is available; in cases where source code is
+ not available, we might specify the signature of the offending code.
+ For more information, see bug 31724.</p>
+
+
+ <h3><a name="XLINT">The -Xlint option</a></h3>
+
+ <p><code>-Xlint:ignore,error,warning</code> will set the level for
+ all Xlint warnings. <code>-Xlint</code>, alone, is an
+ abbreviation for <code>-Xlint:warning</code>.</p>
+
+ <p>The <code>-Xlintfile:lint.properties</code> allows fine-grained
+ control. In tools.jar, see
+ <code>org/aspectj/weaver/XlintDefault.properties</code> for the
+ default behavior and a template to copy. </p>
+
+ <p> More <code>-Xlint</code> warnings are supported now, and
+ we may add disabled warnings in subsequent bug-fix releases of 1.1.
+ Because the configurability allows users to turn off
+ warnings, we will be able to warn about more potentially
+ dangerous situations, such as the potentially unsafe casts used by
+ very polymorphic uses of proceed in around advice. </p>
+
+ <h3><a name="NO_SOURCE">Source-specific options</a></h3>
+
+ <p> Because AspectJ 1.1 does not generate source code after
+ weaving, the source-code-specific options -preprocess, -usejavac,
+ -nocomment and -workingdir options are meaningless and so not
+ supported. </p>
+
+ <h3><a name="NO_STRICT_LENIENT">The -strict and -lenient
+ options</a></h3>
+
+ <p> Because AspectJ 1.1 uses the Eclipse compiler, which has its
+ own mechanism for changing strictness, we no longer support the
+ -strict and -lenient options. </p>
+
+ <h3><a name="NO_PORTING">The -porting option</a></h3>
+
+ <p> AspectJ 1.1 does not have a -porting option.</p>
+
+ <h3><a name="13_REQUIRED">J2SE 1.3 required</a></h3>
+
+ <p>Because we build on Eclipse, the compiler will no longer run
+ under J2SE 1.2. You must run the compiler (and all tools based on
+ the compiler) using J2SE 1.3 or later. The code generated by the
+ compiler can still run on Java 1.1 or later VM's if compiled against
+ the correct runtime libraries.</p>
+
+ <h3><a name="DEFAULT_CONSTRUCTOR_CONFLICT">Default
+ constructors</a></h3>
+
+ <p> AspectJ 1.1 does not allow the inter-type definition of a
+ zero-argument constructor on a class with a visible default
+ constructor. So this is no longer allowed: </p>
+
+ <PRE>
+ class C {}
+
+ aspect A {
+ C.new() {} // was allowed in 1.0.6
+ // is a "multiple definitions" conflict in 1.1
+ }
+ </PRE>
+
+ <p> In the Java Programming Language, a class defined without a
+ constructor actually has a "default" constructor that takes no
+ arguments and just calls <code>super()</code>. </p>
+
+ <p> This default constructor is a member of the class like any other
+ member, and can be referenced by other classes, and has code generated
+ for it in classfiles. Therefore, it was an oversight that AspectJ
+ 1.0.6 allowed such an "overriding" inter-type constructor definition.
+ </p>
+
+ <h3><a name="SUPER_IFACE_INITS">Initialization join points for
+ super-interfaces</a></h3>
+
+ <p> In AspectJ, interfaces may have non-static members due to
+ inter-type declarations. Because of this, the semantics of AspectJ
+ defines the order that initializer code for interfaces is run.
+ </p>
+
+ <p> In the semantics document for AspectJ 1.0.6, the following
+ promises were made about the order of this initialization:
+ </p>
+
+ <ol>
+ <li>a supertype is initialized before a subtype</li>
+ <li>initialized code runs only once</li>
+ <li>initializers for supertypes run in left-to-right order</li>
+ </ol>
+
+ <p> The first two properties are important and are preserved in
+ AspectJ 1.1, but the third property is and was ludicrous, and was
+ never properly implemented (and never could be) in AspectJ 1.0.6.
+ Consider: </p>
+
+ <PRE>
+ interface Top0 {}
+ interface Top1 {}
+ interface I extends Top0, Top1 {}
+ interface J extends Top1, Top0 {}
+
+ class C implements I, J {}
+ // I says Top0's inits must run before Top1's
+ // J says Top1's inits must run before Top0's
+
+ aspect A {
+ int Top0.i = foo("I'm in Top0");
+ int Top1.i = foo("I'm in Top1");
+ static int foo(String s) {
+ System.out.println(s);
+ return 37;
+ }
+ }
+ </PRE>
+
+ <p> This was simply a bug in the AspectJ specification. The correct
+ third rule is:
+ </p>
+
+ <blockquote>the initializers for a type's superclass are run before the
+ initializers for its superinterfaces.
+ </blockquote>
+
+
+ <h3><a name="VOID_FIELD_SET">Field Set Join Points</a></h3>
+
+ <p> In AspectJ 1.0.6, the join point for setting a field F had, as a
+ return type, F's type. This was "java compatible" because
+ field assignment in java, such as "Foo.i = 37", is in fact an
+ expression, and does in fact return a value, the value that the
+ field is assigned to.
+ </p>
+
+ <p> This was never "java programmer compatible", however, largely
+ because programmers have absorbed the good style of rarely using an
+ assignment statement in a value context. Programmers typically expect
+ "Foo.i = 37" not to return a value, but to simply assign a value. </p>
+
+ <p> Thus, programmers typically wanted to write something like:
+ </p>
+
+ <PRE>
+ void around(): set(int Foo.i) {
+ if (theSetIsAllowed()) {
+ proceed();
+ }
+ }
+ </PRE>
+
+ <p> And were confused by it being a compile-time error. They weren't
+ confused for long, and soon adapted to writing:
+ </p>
+
+ <PRE>
+ int around(): set(int Foo.i) {
+ if (theSetIsAllowed()) {
+ return proceed();
+ } else {
+ return Foo.i;
+ }
+ }
+ </PRE>
+
+ <p> But there was definitely a short disconnect. </p>
+
+ <p> On top of that, we were never shown a convincing use-case for
+ returning an interesting value from a set join point. When we
+ revisited this issue, in fact, we realized we had a long-standing bug
+ in 1.0.6 dealing with the return value of pre-increment expressions
+ (such as ++Foo.i) that nobody had found because nobody cares about the
+ return value of such join points.
+ </p>
+
+ <p> So, because it's easier to implement, and because we believe that
+ this is the last possibility to make the semantics more useful, we
+ have made set join points have a void return type in 1.1. </p>
+
+ <h3><a name="XNOINLINE">The -XnoInline Option</a></h3>
+
+ <p> The <code>-XnoInline</code>
+ option to indicate that no inlining of any kind should be done. This
+ is purely a compiler pragma: No program semantics (apart from stack
+ traces) will be changed by the presence or absence of this option.
+ </p>
+
+ <h3><a name="TARGET_TYPES_MADE_PUBLIC">Target types made
+ public</a></h3>
+
+ <p> Even in 1.0.6, the AspectJ compiler has occasionally needed to
+ convert the visibility of a package-level class to a public one. This
+ was previously done in an ad-hoc basis that took whole-program
+ analysis into account. With the incremental compilation model of
+ AspectJ 1.1, we can now specify the occasions when the compiler makes
+ these visibility changes.
+ </p>
+
+ <p> In particular, the types used in the <code>this</code>,
+ <code>target</code>, and <code>args</code> pointcuts are made public,
+ as are the super-types from <code>declare parents</code> and the
+ exception type from <code>declare soft</code>.
+ </p>
+
+ <p> We believe the visibility changes could be avoided in the future
+ with various implementation tricks if they become a serious
+ concern, but did not encounter them as such a concern when they were
+ done in the 1.0.6 implementation. </p>
+
+<h3><a name="STRINGBUFFER">String + now advised</a></h3>
+
+<p> In Java, the + operator sometimes results in StringBuffer objects
+being created, appended to, and used to generate a new String. Thus,
+</p>
+
+<PRE>
+class Foo {
+ String makeEmphatic(String s) {
+ return s + "!";
+ }
+}
+</PRE>
+
+<p> is approximately the same at runtime as
+</p>
+
+<PRE>
+class Foo {
+ String makeEmphatic(String s) {
+ return new StringBuffer(s).append("!").toString();
+ }
+}
+</PRE>
+
+
+<p> In the design process of AspectJ 1.0.6 we didn't expose those
+StringBuffer methods and constructors as join points (though we did
+discuss it), but in 1.1 we do. </p>
+
+<p> This change is likely to affect highly wildcarded aspects, and can
+do so in surprising ways. In particular:
+</p>
+
+<PRE>
+class A {
+ before(int i): call(* *(int)) && args(i) {
+ System.err.println("entering with " + i);
+ }
+}
+</PRE>
+
+<p> may result in a stack overflow error, since the argument to
+println is really </p>
+
+<PRE>
+new StringBuffer("entering with ").append(i).toString()
+</PRE>
+
+<p> which has a call to StringBuffer.append(int). In such cases, it's
+worth restricting your pointcut, with something like one of:
+</p>
+
+<PRE>
+call(* *(int)) && args(i) && !within(A)
+call(* *(int)) && args(i) && !target(StringBuffer)
+</PRE>
+
+<h3><a name="ONE_FOUR_METHOD_SIGNATURES">The -1.4 flag and method signatures</a></h3>
+
+<p> Consider the following aspect
+</p>
+
+<PRE>
+public aspect SwingCalls {
+
+ pointcut callingAnySwing(): call(* javax.swing..*+.*(..));
+
+ before(): callingAnySwing() {
+ System.out.println("Calling any Swing");
+ }
+}
+</PRE>
+
+<p> And then consider the two statements
+</p>
+
+<PRE>
+ JFrame frame = new JFrame();
+ frame.setTitle("Title");
+</PRE>
+
+<p> According to the Java Language Specification version 2, the call
+to <code>frame.setTitle("Title")</code> should always produce the
+bytecode for a call to <code>javax.swing.JFrame.setTitle</code>.
+However, older compilers (and eclipse when run without the
+<code>-1.4</code> flag) will generate the bytecode for a call to
+<code>java.awt.Frame.setTitle</code> instead since this method is not
+overriden by JFrame. The AspectJ weaver depends on the correctly
+generated bytecode in order to match patterns like the one you show
+correctly. </p>
+
+<p> This is a good example of why the pattern <code>call(* *(..)) &&
+target(JFrame)</code> is the recommended style. In general, OO
+programmers don't want to care about the static type of an object at a
+call site, but only want to know the dynamic instanceof behavior which
+is what the target matching will handle. </p>
+
+
+<h2><a name="knownLimitations">Known limitations</a></h2>
+
+<p>The AspectJ 1.1.0 release contains a small number of known limitations
+relative to the AspectJ 1.1 language.
+For the most up-to-date information about known limitations in an
+AspectJ 1.1 release, see the bug database at
+ <a href="http://bugs.eclipse.org/bugs">http://bugs.eclipse.org/bugs</a>,
+especially the open bugs for the
+<a href="http://bugs.eclipse.org/bugs/buglist.cgi?product=AspectJ&component=Compiler&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED">
+ compiler</a>,
+<a href="http://bugs.eclipse.org/bugs/buglist.cgi?product=AspectJ&component=IDE&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED">
+ IDE support</a>,
+<a href="http://bugs.eclipse.org/bugs/buglist.cgi?product=AspectJ&component=Doc&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED">
+ documentation</a>, and
+<a href="http://bugs.eclipse.org/bugs/buglist.cgi?product=AspectJ&component=Ant&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED">
+ Ant tasks</a>.
+Developers should know about bugs marked with the "info" keyword
+because those bugs reflect failures to implement the 1.1 language perfectly.
+These might be fixed during the 1.1 release cycle; find them using the query
+ <a href="http://bugs.eclipse.org/bugs/buglist.cgi?product=AspectJ&keywords=info">
+ http://bugs.eclipse.org/bugs/buglist.cgi?product=AspectJ&keywords=info</a>
+
+For ajc's 1.1 implementation limitations, see
+ <a href="progguide/implementation.html">
+ Programming Guide Appendix: "Implementation Notes"</a>.
+
+</p>
+</body> </html>
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