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+© Copyright 2009 Contributors.
+All rights reserved.
+</small></div>
+
+<h1>AspectJ 1.6.4 Readme</h1>
+
+<ul>
+<li><a href="#compilation">Compilation times</a></li>
+<li><a href="#language">Language enhancements</a></li>
+<li><a href="#bugsfixed">Bugs fixed</a></li>
+<li><a href="#whatsnext">What's next?</a></li>
+</ul>
+<hr>
+<a name="compilation"/>
+<H4>Compilation times</h4>
+<p>In AspectJ 1.6.4 the goal was to improve the IDE experience, through a combination of improved compilation speed (both full
+builds and incremental builds), improved support for multiple-project configurations, and improved feedback in the editor. The
+following sections go into details on each of those topics.</p>
+
+<p><B>Full Compilation</b></p>
+<p>As an example project, all the measurements here are based on the modified JDT compiler that AspectJ uses internally. It is
+1100 source files and includes aspects that affect around 850 join points. Here are the full build times in AJDT:
+</p>
+<p>
+<code><pre>
+AJDT 1.6.3 (uses AspectJ 1.6.3)
+21352ms
+21597ms
+
+AJDT 1.6.5dev builds (use AspectJ 1.6.4)
+19802ms
+19504ms
+</pre></code>
+</p>
+<p>
+About 1.5-2 seconds faster for this example.
+</p>
+<p><b>Incremental Compilation and multi-project scenarios</b></p>
+<p>In most common project configurations there are multiple eclipse projects in some kind of dependency hierarchy. Depending on
+what changes in a top level project, those downstream may need to be rebuilt. The analysis around this area has greatly improved
+in AspectJ 1.6.4, and this has resulted in much reduced incremental build times. The example timed here is around 20 AspectJ
+projects in a hierarchy, and a change is made to a source file in the top level project and build times are observed for the
+downstream projects.</p>
+<p>The timings reported here are accessible to anyone with AJDT installed - just open the 'AJDT Event Trace View' and it will
+report ongoing information about what the compiler/weaver and AJDT are up to. Be aware that data is only recorded in this view
+if it is open - so for optimal performance it should be shutdown, but it is useful for debugging scenarios or collecting
+basic benchmark numbers. Within the event trace view output, the time recorded for 'time spent in AJDE' represents the time
+spent in the compiler: analysing what has changed on the classpath, building code, weaving code.
+</p>
+<p>Initially this is using AJDT 1.6.2 (which embeds AspectJ 1.6.3):</p>
+<p>
+<code><pre>
+Type of change: adding a new method to a type
+Project build times (first one is the compile of our change, the rest are for downstream projects):
+462ms, 4ms, 145ms, 8ms, 9ms, 287ms, 471ms, 222ms, 1028ms, 143ms, 505ms, 199ms, 261ms, 1224ms,
+321ms, 704ms, 75ms, 233ms, 257ms
+Summary: Total time spent in the compiler for that change: <b>6558ms</b>
+---
+Type of change: whitespace change (adding just a harmless space character)
+Project build times (first one is the compile of our change, the rest are for downstream projects):
+229ms, 5ms, 10ms, 9ms, 10ms, 79ms, 43ms, 62ms, 80ms, 37ms, 64ms, 32ms, 79ms,
+154ms, 94ms, 189ms, 72ms, 144ms, 205ms
+Summary: Total time spent in the compiler for that change: <b>1597ms</b>
+</pre></code>
+</p>
+<p>Now with AspectJ 1.6.5 dev builds (which embed AspectJ 1.6.4):</p>
+<p>
+<code><pre>
+Type of change: adding a new method to a type
+Project build times (first one is the compile of our change, the rest are for downstream projects):
+288ms, 3ms, 143ms, 2ms, 2ms, 162ms, 244ms, 89ms, 489ms, 113ms, 277ms, 108ms, 143ms, 626ms,
+135ms, 260ms, 2ms, 96ms, 6ms
+Summary: Total time spent in the compiler for that change: <b>3188ms</b> down from 6558ms
+
+Type of change: whitespace change (adding just a harmless space character)
+Project build times (first one is the compile of our change, the rest are for downstream projects):
+101ms, 1ms, 1ms, 1ms, 0ms, 1ms, 1ms, 1ms, 1ms, 1ms, 0ms, 1ms, 1ms, 2ms, 0ms, 1ms, 0ms, 2ms, 2ms
+Summary: Total time spent in the compiler for that change: <b>118ms</b> (down from 1597ms)
+</pre></code>
+</p>
+<p>
+Improvements all round, and almost instant builds now for whitespace changes, even in large
+project setups.
+</p>
+<p>In addition the compilation times are also improved in situations where AspectJ projects depend upon Java projects and
+where aspectpath is used.
+</p>
+<h4>Better editor feedback</h4>
+<p>Under <a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=246393">bug 246393</a> the problem has been addressed where
+sometimes spurious errors would appear throughout the editor for a file in AJDT when just one single simple syntax errors exists. More
+detail on this problem can be found
+<a href="http://andrewclement.blogspot.com/2009/02/aspectj-fixing-reverse-cascade-errors.html">here</a>.
+</p>
+<hr>
+<a name="language"/>
+<H4>Language Enhancements</h4>
+<p><b>Optimizing support for maintaining per join point state</b></p>
+<p>The traditional way to maintain state on a per join point basis involves using the JoinPoint.StaticPart as a key
+into a map:
+<code><pre>
+aspect X pertypewithin(*) {
+ Map<JoinPoint.StaticPart,Timer> timerMap = ...
+
+ Object around(): execution(public * *(..)) {
+ Timer timerToUse = timerMap.get(thisJoinPointStaticPart);
+ timerToUse.start();
+ Object o = proceed();
+ timerToUse.stop();
+ return o;
+ }
+}
+</pre></code>
+<p>These map lookups are slow. In AspectJ 1.6.4 there is a new getId() method on the JoinPoint.StaticPart object.
+The ids for all affected join points within a target type are unique (and start from 0) - they are ideal for
+array lookups. So using this the above aspect can be rewritten:
+</p>
+
+<code><pre>
+aspect X pertypewithin(*) {
+ Timer timerArray = ...
+
+ Object around(): execution(public * *(..)) {
+ Timer timerToUse = timerArray[thisJoinPointStaticPart.getId()];
+ timerToUse.start();
+ Object o = proceed();
+ timerToUse.stop();
+ return o;
+ }
+}
+</pre></code>
+<p>much faster. Just be aware that the ids are only unique within an affected target type - hence the use of pertypewithin
+in this example to ensure there is an aspect instance (and so a different array) for each advised type.</p>
+<p>See related <a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=89009">bug 89009</a> for the full discussion</p>
+
+<h4>@DeclareMixin</h4>
+<p>The annotation style declare parents support (@DeclareParents) has been (rightly) criticized because it really does not offer
+an equivalent to what is possible with code style declare parents, it really offers a mixin strategy. It also has limitations
+such as the delegate instance used to satisfy any method invocations on an affected target cannot access the object instance for
+which it is acting as a delegate. To address these concerns a proper mixin notation has been introduced that makes it more clear
+that a mixin strategy is being employed and it addresses the problem of the mixin delegate accessing the affected target instance.
+</p>
+<p>
+The @DeclareMixin annotation is attached to a factory method which returns instances of the delegate. Here is a basic example:
+</p>
+<code><pre>
+ // The factory method that can build the delegate instance is annotated with @DeclareMixin.
+ // The annotation value defines the type pattern for targets of the mixin.
+ // The parameter is the object for which a delegate is being constructed.
+ // The interface that will be mixed in is the return value of the factory method.
+ @DeclareMixin("org.xyz..*")
+ public static SomeInterface createDelegate(Object instance) {
+ return new SomeImplementation(instance);
+ }
+</pre></code>
+<p>More examples are <a href="http://www.eclipse.org/aspectj/doc/released/adk15notebook/ataspectj-itds.html">here in the online
+documentation</a>.</p>
+<p>Going forward attempts will be made to try and make @DeclareParents behave more like code style - if this cannot
+be done it is likely to be deprecated.</p>
+<hr>
+<a name="bugsfixed"/>
+<h4>Bugs fixed</h4>
+<p>The complete list of issues resolved for AspectJ 1.6.4 (more than 70) can be found with
+this bugzilla query:
+<ul>
+<li><a href="https://bugs.eclipse.org/bugs/buglist.cgi?query_format=advanced&short_desc_type=allwordssubstr&short_desc=&product=AspectJ&target_milestone=1.6.4&long_desc_type=allwordssubstr&long_desc=&bug_file_loc_type=allwordssubstr&bug_file_loc=&status_whiteboard_type=allwordssubstr&status_whiteboard=&keywords_type=allwords&keywords=&bug_status=RESOLVED&bug_status=VERIFIED&bug_status=CLOSED&emailtype1=substring&email1=&emailtype2=substring&email2=&bugidtype=include&bug_id=&votes=&chfieldfrom=&chfieldto=Now&chfieldvalue=&cmdtype=doit&order=Reuse+same+sort+as+last+time&field0-0-0=noop&type0-0-0=noop&value0-0-0=">Bugs resolved</a>
+</ul>
+<hr>
+<a name="whatsnext"/>
+<h4>What's next?</h4>
+<p><b>More incremental build enhancements</b></p>
+<p>A number of situations still exist where incremental compile speeds still needs optimizing, particular when capabilities
+like aspectpath or inpath are used.</p>
+<p><b>Build state persistence</b></p>
+<p>Between restarts of Eclipse the state of each project is not recorded - hence full builds are required upon restart. The
+state (and associated relationship model) should be persisted between restarts, but both of these need a review first to ensure
+they are not larger than they need to be.
+</p>
+<p><b>Memory consumption</b</p>
+<p>Both for source compilation and load-time weaving scenarios. The size of the model in the IDE needs reviewing, and also the
+type map within the weaver. Although the type map uses Weak/Soft references to try and better control how it uses memory, the JVM
+policies for managing these references vary wildly and so some work needs to be done to allow for these differences.
+<hr>
+
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