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<title>AspectJ 1.9.19 Readme</title>
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<div align="right"><small>&copy; Copyright 2022 Contributors. All rights reserved.</small></div>

<h1>AspectJ 1.9.19</h1>

<p>
  Please note that Bugzilla for issue management is deprecated and new issues should be filed as
  <a href="https://github.com/eclipse/org.aspectj/issues/new">GitHub issues</a>.
  The list of issues addressed for 1.9.19 can be found here:
  <ul>
    <li><a href="https://github.com/eclipse/org.aspectj/issues?q=is%3Aissue+is%3Aclosed++milestone%3A1.9.19">GitHub 1.9.19</a></li>
    <li><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=1.9.19">Bugzilla 1.9.19</a></li>
  </ul>
</p>

<h2>New features</h2>

<p>
  AspectJ 1.9.19 supports <a href="https://openjdk.java.net/projects/jdk/19/">Java 19</a> and its final, preview and
  incubator features, such as:
</p>
<ul>
  <li>Record patterns (preview)</li>
  <li>Virtual threads (preview)</li>
  <li>Pattern matching for <tt>switch</tt> (preview 3)</li>
  <li>Structured concurrency (incubator)</li>
</ul>

<p>
  Please note that the upstream Eclipse Java Compiler (ECJ) which the AspectJ Compiler (AJC) is a fork of still has some
  open issues concerning Java 19 preview feature support, see the list in
  <a href="https://github.com/eclipse/org.aspectj/issues/184#issuecomment-1272254940">this comment</a>. AJC therefore
  inherits the same problems for the specific cases described in the linked issues.
</p>

<h2>Improvements</h2>

<ul>
  <li>
    Improve condy (constant dynamic) support. Together with some custom compilation or weaving options, this helps to
    avoid a problem when using JaCoCo together with AspectJ, see
    <a href="https://github.com/eclipse/org.aspectj/issues/170#issuecomment-1214163297">this comment in #170</a> for
    more details.
  </li>
</ul>

<h2>Code examples</h2>

<p>
  You can find some sample code in the AspectJ test suite under the respective AspectJ version in which the features
  were first supported (possibly as JVM preview features):
</p>
<ul>
  <li>
    <a href="https://github.com/eclipse/org.aspectj/tree/master/tests/features198/java17">
      Pattern matching for switch (preview 1)
    </a>
  </li>
  <li>
    <a href="https://github.com/eclipse/org.aspectj/tree/master/tests/features199/java18">
      Pattern matching for switch (preview 2)
    </a>
  </li>
  <li>
    <a href="https://github.com/eclipse/org.aspectj/tree/master/tests/features1919/java19">
      Pattern matching for switch (preview 3), record patterns (preview 1)
    </a>
  </li>
  <li>
    Please note that presently there is no specific sample code for virtual threads and structured concurrency in the
    AspectJ code base, because these are just new APIs, no Java language features. You can find sample code for these
    concurrency features elsewhere, e.g. in the corresponding JEPs. In AspectJ, they should just work transparently
    like any other Java API.
  </li>
</ul>

<h2>Other changes and bug fixes</h2>

<ul>
  <li>
    Fix (or rather work around) an old bug occurring when compiling or weaving code using ITD to declare annotations
    with <tt>SOURCE</tt> retention on types, methods, constructors or fields. While declaring such annotations does not
    make sense to begin with, at least the AspectJ weaver or compiler should handle the situation gracefully, which now
    it does by simply ignoring errors caused by it. See <a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=366085">
    Bugzilla #366085</a> and <a href="https://github.com/eclipse/org.aspectj/pull/196">pull request #196</a>. Better
    than this workaround would be for the compiler or weaver to actually print a warning when meeting source level
    annotations in declare statements. Hence, follow-up issue
    <a href="https://github.com/eclipse/org.aspectj/issues/201">#201</a> was created.
  </li>
  <li>
    Remove legacy AspectJ Browser code and documentation.
  </li>
  <li>
    Thanks to Andrey Turbanov for several clean code contributions.
  </li>
</ul>

<h2>AspectJ usage hints</h2>

<h3>AspectJ compiler build system requirements</h3>

<p>
  Since 1.9.7, the AspectJ compiler <tt>ajc</tt> (contained in the <tt>aspectjtools</tt> library) no longer works on
  JDKs 8 to 10. The minimum compile-time requirement is now JDK 11 due to upstream changes in the Eclipse Java Compiler
  (subset of JDT Core), which AspectJ is a fork of. You can still compile to legacy target versions as low as Java 1.3
  when compiling plain Java code or using plain Java ITD constructs which do not require the AspectJ runtime
  <tt>aspectjrt</tt>, but the compiler itself needs JDK 11+. Just like in previous AspectJ versions, both the runtime
  <tt>aspectjrt</tt> and the load-time weaver <tt>aspectjweaver</tt> still only require JRE 8+.
</p>

<h3>Use LTW on Java 16+</h3>

<p>
  Please note that if you want to use load-time weaving on Java 16+, the weaving agent collides with
  <a href="https://openjdk.java.net/jeps/396">JEP 396 (Strongly Encapsulate JDK Internals by Default)</a> and related
  subsequent JEPs. Therefore, you need to set the JVM parameter <tt>--add-opens java.base/java.lang=ALL-UNNAMED</tt> in
  order to enable aspect weaving. This is due to the fact that the weaver uses internal APIs for which we have not found
  an adequate replacement yet when defining classes in different classloaders.
</p>

<h3>Compile with Java preview features</h3>

<p>
  For features marked as preview on a given JDK, you need to compile with <tt>ajc --enable-preview</tt> and run with
  <tt>java --enable-preview</tt> on that JDK.
</p>
<p>
  Please note that you cannot run code compiled with preview features on any other JDK than the one used for
  compilation. For example, records compiled with preview on JDK 15 cannot be used on JDK 16 without recompilation. This
  is a JVM limitation unrelated to AspectJ. Also, e.g. sealed classes are preview-1 on JDK 15 and preview-2 on JDK 16.
  You still need to recompile, no matter what.
</p>

<hr>

<p>
  <b>Available:</b> 1.9.19 on 21-Dec-2022
</p>

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