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<h1>AspectJ 1.9.0.RC1 Readme</h1>

<p>The full list of resolved issues in 1.9.0 is available 
<a href="https://bugs.eclipse.org/bugs/buglist.cgi?bug_status=RESOLVED&bug_status=VERIFIED&bug_status=CLOSED&f0=OP&f1=OP&f3=CP&f4=CP&j1=OR&list_id=16866879&product=AspectJ&query_format=advanced&target_milestone=1.9.0">here</a></h2>.</p>

<ul>
<li>1.9.0.RC1 available 20-Oct-2017
</ul>

<p>Available from this maven repository as 1.9.0.RC1:
<pre><code>
&lt;repository&gt;
    &lt;id&gt;repo.spring.io&lt;/id&gt;
    &lt;name&gt;Spring milestones&lt;/name&gt;
    &lt;url&gt;http://repo.spring.io/milestone&lt;/url&gt;
&lt;/repository&gt;
</code></pre>

<br>
<p>Or downloadable from the <a href="https://eclipse.org/aspectj/downloads.php">download page</a>.

<h2>Notable changes</h2>

<p>This is the first release candidate of AspectJ 1.9.0 - the version of AspectJ to be based on Java9.  It includes
a recent version of the Eclipse Java9 compiler (from jdt core, commit #062ac5d7a6bf9).</p>


<h3>Automatic Modules</h3>
<p>AspectJ can now be used with the new module system available in Java9. The key jars in AspectJ have been given automatic module names.

The automatic module name is <tt>org.aspectj.runtime</tt> for the <tt>aspectjrt</tt> module:</p>
<pre><code>
$ java --module-path &lt;pathto&gt;/lib/aspectjrt.jar --list-modules | grep aspectj

org.aspectj.runtime file:///&lt;pathto&gt;/lib/aspectjrt.jar automatic

</code></pre>

<p>And similarly <tt>org.aspectj.weaver</tt> and <tt>org.aspectj.tools</tt> for <tt>aspectjweaver</tt> and <tt>aspectjtools</tt> respectively:</p>

<pre><code>
$ java --module-path &lt;pathto&gt;/lib/aspectjweaver.jar --describe-module org.aspectj.weaver

org.aspectj.weaver file:///&lt;pathto&gt;/lib/aspectjweaver.jar automatic
requires java.base mandated
contains aj.org.objectweb.asm
contains aj.org.objectweb.asm.signature
contains org.aspectj.apache.bcel
contains org.aspectj.apache.bcel.classfile
contains org.aspectj.apache.bcel.classfile.annotation
contains org.aspectj.apache.bcel.generic
contains org.aspectj.apache.bcel.util
contains org.aspectj.asm
contains org.aspectj.asm.internal
...
</code></pre>

<h3>Building woven modules</h3>
<p>AspectJ understands module-info.java source files and building modules that include aspects. Here is an example:</p>

<pre><code>
<b>module-info.java</b>

module demo {
	exports pkg;
	requires org.aspectj.runtime;
}


<b>pkg/Demo.java</b>

package pkg;

public class Demo {
	public static void main(String[] argv) {
		System.out.println("Demo running");
	}
}


<b>otherpkg/Azpect.java</b>

package otherpkg;

public aspect Azpect {
	before(): execution(* *(..)) && !within(Azpect) {
		System.out.println("Azpect running");
	}
}

</code></pre>

<p>We can now build those into a module:</p>

<pre><code>
$ ajc -1.9 module-info.java otherpkg/Azpect.java pkg/Demo.java -outjar demo.jar

...
module-info.java:3 [error] org.aspectj.runtime cannot be resolved to a module
...
</code></pre>

<p>Wait, that failed!  Yes, <tt>aspectjrt.jar</tt> (which includes the required <tt>org.aspectj.weaver</tt> module) wasn't supplied.
We need to pass it on the module-path:</p>

<pre><code>
$ ajc -1.9 --module-path &lt;pathto&gt;/aspectjrt.jar module-info.java otherpkg/Azpect.java pkg/Demo.java -outjar demo.jar

</code></pre>

<p>Now we have a demo module we can run:</p>

<pre><code>
$ java --module-path &lt;pathto&gt;/aspectjrt.jar:demo.jar --module demo/pkg.Demo

Azpect running
Demo running
</code></pre>

<p>That's it!</p>


<h3>Binary weaving with modules</h3>

<p>A module is really just a jar with a module-info descriptor. As such you can simply pass a module on the <tt>inpath</tt>
and binary weave it with other aspects.  Take the module we built above, let's weave into it again:</p>

<pre><code>extra/AnotherAzpect.java

package extra;

public aspect AnotherAzpect {
	before(): execution(* *(..)) && !within(*Azpect) {
		System.out.println("AnotherAzpect running");
	}
}
</code></pre>

<pre><code>
$ ajc -inpath demo.jar AnotherAzpect.java -outjar newdemo.jar</code></pre>

<p>Notice how there was no complaint here that the <tt>org.aspectj.runtime</tt> module hadn't been passed in. That is because <tt>inpath</tt>
was being used which doesn't treat specified jars as modules (and so does not check dependencies). There is no <tt>module-inpath</tt> right now.

<p>Because the new jar produced includes the compiled aspect, the module-info specification inside is still correct, so we can run it
exactly as before:</p>

<pre><code>$ java --module-path ~/installs/aspectj190rc1/lib/aspectjrt.jar:newdemo.jar --module demo/pkg.Demo

Azpect running
AnotherAzpect running
Demo running
</code></pre>

<h3>Faster Spring AOP</h3>
<p>Dave Syer recently created a series of benchmarks for checking the speed of Spring-AspectJ: 
<tt><a href="https://github.com/dsyer/spring-boot-aspectj">https://github.com/dsyer/spring-boot-aspectj</a></tt>

<p>Here we can see the numbers for AspectJ 1.8.11 (on an older Macbook Pro):

<pre><code>
Benchmark                 (scale)  Mode  Cnt   Score   Error  Units
StartupBenchmark.ltw          N/A  avgt   10   2.553 ~ 0.030   s/op
StartupBenchmark.ltw_100      N/A  avgt   10   2.608 ~ 0.046   s/op
StartupBenchmark.spring     v0_10  avgt   10   2.120 ~ 0.148   s/op
StartupBenchmark.spring     v1_10  avgt   10   2.219 ~ 0.066   s/op
StartupBenchmark.spring    v1_100  avgt   10   2.244 ~ 0.030   s/op
StartupBenchmark.spring    v10_50  avgt   10   2.950 ~ 0.026   s/op
StartupBenchmark.spring    v20_50  avgt   10   3.854 ~ 0.090   s/op
StartupBenchmark.spring   v20_100  avgt   10   4.003 ~ 0.038   s/op
StartupBenchmark.spring     a0_10  avgt   10   2.067 ~ 0.019   s/op
StartupBenchmark.spring     a1_10  avgt   10   2.724 ~ 0.023   s/op
StartupBenchmark.spring    a1_100  avgt   10   2.778 ~ 0.057   s/op
StartupBenchmark.spring    a10_50  avgt   10   7.191 ~ 0.134   s/op
StartupBenchmark.spring   a10_100  avgt   10   7.191 ~ 0.168   s/op
StartupBenchmark.spring    a20_50  avgt   10  11.541 ~ 0.158   s/op
StartupBenchmark.spring   a20_100  avgt   10  11.464 ~ 0.157   s/op
</code></pre>

<p>So this is the average startup of an app affected by aspects applying to the beans involved.
Where numbers are referenced the first is the number of aspects/pointcuts and the second
is the number of beans.  The 'a' indicates an annotation based pointcut vs a non-annotation 
based pointcut ('v'). Notice things are much worse for annotation based pointcuts.  At 20
pointcuts and 50 beans the app is 9 seconds slower to startup.
<br>

<p>In AspectJ 1.8.12 and 1.9.0.RC1 some work has been done here. The key change is to recognize that the use
of annotations with runtime retention is much more likely than annotations with class level
retention. Retrieving annotations with class retention is costly because we must open the
bytes for the class file and dig around in there (vs runtime retention which are immediately
accessible by reflection on the types). In 1.8.11 the actual type of the annotation involved
in the matching is ignored and the code will fetch *all* the annotations on the type/method/field
being matched against. So even if the match is looking for a runtime retention annotation, we
were doing the costly thing of fetching any class retention annotations. In 1.8.12/1.9.0.RC1
we take the type of the match annotation into account - allowing us to skip opening the classfiles
in many cases. There is also some deeper work on activating caches that were not previously
being used correctly but the primary change is factoring in the annotation type.

<p>What difference does that make?

AspectJ 1.9.0.RC1:
<pre><code>
Benchmark                 (scale)  Mode  Cnt  Score   Error  Units
StartupBenchmark.ltw          N/A  avgt   10  2.568 ~ 0.035   s/op
StartupBenchmark.ltw_100      N/A  avgt   10  2.622 ~ 0.075   s/op
StartupBenchmark.spring     v0_10  avgt   10  2.096 ~ 0.054   s/op
StartupBenchmark.spring     v1_10  avgt   10  2.206 ~ 0.031   s/op
StartupBenchmark.spring    v1_100  avgt   10  2.252 ~ 0.025   s/op
StartupBenchmark.spring    v10_50  avgt   10  2.979 ~ 0.071   s/op
StartupBenchmark.spring    v20_50  avgt   10  3.851 ~ 0.058   s/op
StartupBenchmark.spring   v20_100  avgt   10  4.000 ~ 0.046   s/op
StartupBenchmark.spring     a0_10  avgt   10  2.071 ~ 0.026   s/op
StartupBenchmark.spring     a1_10  avgt   10  2.182 ~ 0.032   s/op
StartupBenchmark.spring    a1_100  avgt   10  2.272 ~ 0.024   s/op
StartupBenchmark.spring    a10_50  avgt   10  2.557 ~ 0.027   s/op
StartupBenchmark.spring   a10_100  avgt   10  2.598 ~ 0.040   s/op
StartupBenchmark.spring    a20_50  avgt   10  2.961 ~ 0.043   s/op
StartupBenchmark.spring   a20_100  avgt   10  3.093 ~ 0.098   s/op
</code></pre>

<p>Look at the a20_100 case - instead of impacting start time by 9 seconds, it impacts it by 1 second.

<h3>More to come...</h3>

<ul>
<li><p>Eclipse JDT Java 9 support is still being actively worked on and lots of fixes will be coming through over the next few months
and included in AspectJ 1.9.X revisions.</p>

<li><p>AspectJ does not currently modify <tt>module-info.java</tt> files. An aspect from one module applying to code in
another module clearly introduces a dependency between those two modules. There is no reason - other than time! - that
this can't be done. (<a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=526244">Issue 526244</a>)</p>

<li><p>Related to that AspectJ, on detection of aspects should be able to automatically introduce the <tt>requires org.aspectj.runtime</tt> to
the <tt>module-info</tt>. (<a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=526242">Issue 526242</a>)</p>

<li><p>Module aware variants of AspectJ paths: <tt>--module-inpath</tt>, <tt>--module-aspectpath</tt>. (<a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=526243">Issue 526243</a>)</p>
</ul>

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