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| <h1>OTDT 2.3 - New and Noteworthy</h1> |
| <div class="navigation">On this page: |
| <!--a href="#metrics">• Metrics Plug-in</a--> |
| <!--a href="#configuration">• Configuration</a--> |
| <!--a href="#views">• Views/Dialogs</a--> |
| <!--a href="#assist">• Content Assist</a--> |
| <!--a href="#refactor">• Refactoring</a--> |
| <!--a href="#formatting">• Formatting</a--> |
| <!--a href="#debug">• Run/Debug</a--> |
| <a href="#language">• Language</a> |
| <!--a href="#api">• API</a--> |
| <!--a href="#compiler">• Compiler</a--> |
| <a href="#otre">• Runtime</a> |
| <a href="#otequinox">• OT/Equinox</a> |
| <!--a href="#releng">• Release Engineering</a--> |
| </div> |
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| <col width="20%"> |
| <col width="80%"> |
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| <tbody> |
| <!-- |
| <tr><td colspan="2" id="NAME"><h2>HEADING</h2></td></tr> |
| <tr> |
| <td><p align="right"><b>DESC</b><br> |
| <span class="since">since 0.7.1</span><br> |
| <a class="buglink" title="TITLE" href="https://bugs.eclipse.org/308029">308029</a></p></td> |
| <td><p> |
| |
| </p> |
| <p><img alt="TEXT" src="../images/screenshots/NN07/.png"></p> |
| <p></p> |
| </td> |
| </tr> |
| <div class="listbox"><div class="listing"><pre><code class="keyword">public team class</code> <font color="blue">MyTeam</font> { |
| }</pre></div></div> |
| --> |
| <tr><td colspan="2" id="language"><h2>Language</h2></td></tr> |
| <tr> |
| <td id="java8"><a href="PLUGINS_ROOT/org.eclipse.jdt.doc.user/whatsNew/jdt_whatsnew.html#JavaCompiler"><img align="right" src="../images/java8.png"/></a><br/> |
| <p align="right"><b>Adopt Java 8</b><br/> |
| <br/> |
| <!--span class="since">since 2.3</span><br--> |
| <a class="buglink" target="_blank" title="[java8] adopt and merge implementation of Java 8 from JDT's BETA_JAVA8 branch " href="https://bugs.eclipse.org/384991">384991</a></p></td> |
| <td> |
| <div style="background-color:#fffce4;padding:4px;border:solid 2px #e0e0f0;color:#300080;"><strong>OT/J has been fully integrated with Java™ 8.</strong><br/> |
| This means that lambda expressions, method references, default methods, type annotations etc. can all be used in OT/J programs. |
| Additionally, roles in OT/J can bind to Java 8 classes containing any of these new features. |
| </div> |
| <h3>Grammar challenge</h3> |
| <p>Syntactically, some of the new features in Java 8 look surprisingly similar to OT/J:</p> |
| <ul> |
| <li>The arrow "<code>-></code>" used for lambda expressions is the same token that |
| OT/J uses for <a class="otjldlink" href="OTJLD/s3.html">callout bindings</a> and |
| <a class="otjldlink" href="OTJLD/s3.html#s3.2">role-to-base parameter mappings</a> |
| (see also <a class="otjldlink" href="OTJLD/s4.html#s4.4">4.4</a>).</li> |
| <li>The "<code>@</code>" token used for type annotations (JSR 308) is the same that |
| OT/J uses to denote a <a class="otjldlink" href="OTJLD/s1.html#s1.2.2.b">team anchor</a></li> |
| </ul> |
| <h3>Clean integration</h3> |
| <p> |
| Despite these syntactic similarities, it was not necessary to change OT/J in order to harmonize |
| with the syntax of Java 8. So with the minimal, inevitable restrictions ("team" and "within" |
| are unconditional keywords in OT/J) every legal Java 8 program is also a legal OT/J program. |
| Conversely, every legal OT/J program from earlier versions, is still a legal OT/J program. |
| </p> |
| <h3>Feature interaction</h3> |
| <p> |
| For the most part, the new features in Java 8 can be regarded as orthogonal to features |
| introduced by OT/J: |
| </p> |
| <ul> |
| <li>Lambda expressions in Java 8 are about the details of implementing algorithms</li> |
| <li>Type annotations in Java 8 are about improving the type system</li> |
| <li>Roles and Teams in OT/J are about composing individual objects into a system</li> |
| </ul> |
| <p>With respect to <strong>type checking</strong> the following features required significant |
| work behind the scenes to reconcile the various type rules: generics with enhanced type inference, |
| type annotations and finally: role types, all contribute to a very rich notion of types. |
| Given that type inference in the Eclipse Compiler for Java was completely re-written, |
| adopting that re-write for OT/J required intimate knowledge about that implementation.</p> |
| <p><strong>Inheritance</strong> now has more options due to the introduction of default methods. |
| This poses a new challenge in combination with OT/J's |
| <a href="OTJLD/s1.html#s1.3.1">implicit inheritance</a>, |
| some details of which may still require more work after the 2.3 release. |
| Technically, OT/J now supports two different styles of multiple inheritance, |
| but from the details it is clear that both concepts pursue entirely different goals. |
| It is not expected that these concepts compete for solving any real world design task. |
| </p> |
| </td> |
| </tr> |
| |
| <tr><td colspan="2" id="otre"><h2>Object Teams Runtime Environment</h2></td></tr> |
| <tr> |
| <td><p align="right"><b>New byte code weaver</b><br> |
| <br> |
| <a class="buglink" target="_blank" title="Support runtime weaving " href="https://bugs.eclipse.org/398232">398232</a></p></td> |
| <td><p>Starting with 2.3, OTDT ships with a new byte code weaver as an alternative to the traditional |
| <a href="PLUGINS_ROOT/org.eclipse.objectteams.otdt.doc/guide/features.html#execution">OTRE</a>.</p> |
| <p>This weaver, called "<strong>Object Teams Dynamic Runtime Environment (OTDRE)</strong>" |
| has been developed with the goal to support <strong>runtime weaving</strong>, |
| i.e., to support the integration of roles and teams that are not known during application launch. |
| This capability has been fully implemented, but infrastructure to fully leverage the new flexibility |
| still needs to be developed (think, i.e., of a monitoring console that allows runtime deployment |
| of new monitoring team classes).</p> |
| <p>The OTDRE is implemented using the byte code library <strong>ASM</strong>, |
| as opposed to the BCEL-based implementation of the OTRE. |
| ASM follows a more modern approach, which results in better weaving performance. |
| ASM is also actively maintained, which, unfortunately, is no longer true of BCEL.</p> |
| </td></tr> |
| <tr> |
| <td class="noborder"><a href="#java8"><img align="right" src="../images/java8.png"/></a></td> |
| <td class="noborder"><p>By using the latest version of ASM, the OTDRE is capable of processing class files even of <strong>Java 8</strong>, |
| which is not possible using BCEL. |
| Therefore, the OTDRE is shipped with the specific goal to support Java 8, although it has not yet reached exactly |
| the maturity, which the OTRE has obtained over the years.</p> |
| <p>Both weavers are supported by the compiler, by generating specific infrastructure to be invoked |
| from woven code. Due to the fundamental difference in <strong>weaving schemes</strong>, |
| it is necessary to selected at compile time, which weaver should be targeted. Please see the section on |
| <a href="PLUGINS_ROOT/org.eclipse.objectteams.otdt.doc/guide/weavingscheme.html">target weaving schemes</a> in the developers' guide.</p> |
| </td> |
| </tr> |
| |
| <tr><td colspan="2" id="otequinox"><h2>OT/Equinox</h2></td></tr> |
| <tr> |
| <td><p align="right"><b>Migrate to new Equinox implemen­tation</b><br> |
| <span class="since">since 2.3M2</span><br> |
| <a class="buglink" target="_blank" title="migrate OT/Equinox to the standard OSGi WeavingHook" href="https://bugs.eclipse.org/406518">406518</a></p></td> |
| <td><h3>A mostly compatible re-implementation</h3> |
| <p>The implementation of OT/Equinox has been re-written, |
| which became necessary when Equinox withdrew an "inofficial API" called "Adapter Hooks", |
| on which OT/Equinox had relied for many years.</p> |
| <p>At the surface this should hardly be visible to regular clients of the OT/Equinox technology; |
| the existing extension point |
| <a href="PLUGINS_ROOT/org.eclipse.objectteams.otdt.doc/reference/extension-points/org_eclipse_objectteams_otequinox_aspectBindings.html"><code>aspectBindings</code></a> |
| is supported unchanged.</p> |
| <p>The single surface change regards the way how visibility between a base class and an adapting team is established: |
| In the new implementation each aspect bundle must <strong>export all packages containing one or more team classes</strong>. |
| This is a hard requirement and missing exports will be flagged as an error. |
| A new <strong><a href="#qfAddExport">quick fix</a></strong> is provided to support this task.</p> |
| <h3>Current limitations</h3> |
| <p>A few add-on features of OT/Equinox are currently unimplemented and are planned to be re-added in Luna service releases:</p> |
| <ul> |
| <li><a href="PLUGINS_ROOT/org.eclipse.objectteams.otdt.doc/reference/extension-points/org_eclipse_objectteams_otequinox_aspectBindings.html#e.forcedExports">Forced Exports</a></li> |
| <li><a href="PLUGINS_ROOT/org.eclipse.objectteams.otdt.doc/reference/extension-points/org_eclipse_objectteams_otequinox_liftingParticipant.html">Lifting Participants</a> |
| <li><a href="PLUGINS_ROOT/org.eclipse.objectteams.otdt.doc/reference/extension-points/org_eclipse_objectteams_otequinox_aspectBindingNegotiators.html">Aspect Binding Negotiation</a> |
| </ul> |
| <h3>Details</h3> |
| <p>Previously, we had given advice that OT/Equinox can be <strong>disabled</strong> by removing a particular line |
| from the file <code>configuration/config.ini</code>. This line no longer exists. |
| Instead, OT/Equinox can now be disabled using the following Java property:</p> |
| <pre> -Dot.equinox=false</pre> |
| <p>The new implementation also plays better with Equinox' <strong>lazy loading</strong>: |
| previously, loading and activation of teams was triggered whenever the affected base <em>bundle</em> was activated. |
| Given that team loading/activation could in turn trigger other bundles to be loaded/activated, |
| a lot of loading activity could be observed right during system launch, which was not strictly necessary. |
| The new implementation waits until actually an affected base <em>class</em> is accessed, |
| which is the latest possible point for activating corresponding teams. |
| As a result the impact on the loading sequence could be significantly reduced.</p> |
| <h3>Portability</h3> |
| <p>The new implementation no longer depends on "inofficial API", but relies on the OSGi standard <strong>WeavingHook</strong>. |
| This way, the basic functionality of OT/Equinox should in fact work on other OSGi containers, as well. |
| Of course, using extension points for declaring teams to be activated still depends on Equinox, |
| but this is a well isolated concern and porting this to any other means for configuration |
| should be straight-forward.</p> |
| <h3>Visualization unchanged</h3> |
| <p>As a (partial) proof of compatibility, the existing <strong>OT/Equinox Monitor</strong> view works |
| on top of the new implementation without a single line of code changed.</p> |
| <img src="../images/screenshots/otequinoxMonitor.png" width="519" alt="OT/Equinox Montitor View"/> |
| <p>In fact this view can be used to observe the non-impact of OT/Equinox in two regards:</p> |
| <ul> |
| <li>Teams whose base classes have not yet been loaded will not be known / shown. |
| To see the highlighted BrandingAdaptor, it is necessary to open an about dialog like |
| <code class="UI">Help > Installation Details > Plug-ins</code></li> |
| <li>Role instances adapting a base instance that has been garbage-collected are also removed from memory |
| and hence no longer show in the monitor view (cf. the many zeros in the "# roles" column).</li> |
| </ul> |
| </td> |
| </tr> |
| <tr> |
| <td id="qfAddExport"><p align="right"><b>Quick fix to add aspect export</b><br> |
| <span class="since">since 2.3M2</span><br> |
| <a class="buglink" target="_blank" title="migrate OT/Equinox to the standard OSGi WeavingHook" href="https://bugs.eclipse.org/406518#c37">406518#c37</a></p></td> |
| <td><p>The new implementation of OT/Equinox requires to export all packages containing teams (see above). |
| When this export is missing, an error is flagged against the plugin's manifest and a quick fix is |
| offered for adding the required export in the recommended format. |
| </p> |
| <a href="../images/screenshots/NN23/QFAddAspectExport.png"><img src="../images/screenshots/NN23/QFAddAspectExport.png" width=519 alt="Quick fix to add required aspect export"/></a> |
| <p>Applying the quick fix produces this result:</p> |
| <a href="../images/screenshots/NN23/QFAddAspectExport1.png"><img src="../images/screenshots/NN23/QFAddAspectExport1.png" width=519 alt="Result of the quick fix"/></a> |
| <p id="ot-aspect-host">The screenshot shows a package export with a <em>recommended</em> property <code>ot-aspect-host</code>, |
| which marks the export as intended for the sole purpose of letting woven code call into the team. |
| Additionally, the value of this property identifies the declaring aspect bundle, |
| which is internally used to uniquely identify this package even in situations of split packages. |
| </p> |
| <p>Finally, the export may use one of <code>x-internal</code> or <code>x-friends</code> |
| for preventing unintended use of this package. |
| </p> |
| <p> Once we re-implement the Forced Exports concept (see above), we may consider to remove the |
| additional requirement to export all packages containing teams. |
| </p> |
| </td> |
| </tr> |
| |
| <!-- |
| |
| <tr><td colspan="2" id="debug"><h2>Run / Debug</h2></td></tr> |
| <tr> |
| <td><p align="right"><b>HEADING</b><br> |
| <span class="since">since 2.1M6</span><br> |
| <a class="buglink" title="TITLE" href="https://bugs.eclipse.org/301314">301314</a></p></td> |
| <td><p>PARA</p> |
| </td> |
| </tr> |
| |
| <tr><td colspan="2" id="api"><h2>API</h2></td></tr> |
| <tr> |
| <td><p align="right"><b>HEADING</b><br> |
| <span class="since">since 2.1M6</span><br> |
| <a class="buglink" title="TITLE" href="https://bugs.eclipse.org/301314">301314</a></p></td> |
| <td><p>PARA</p> |
| </td> |
| </tr> |
| |
| <tr><td colspan="2" id="compiler"><h2>Compiler</h2></td></tr> |
| <tr> |
| <td><p align="right"><b>HEADING</b><br> |
| <span class="since">since 2.1M6</span><br> |
| <a class="buglink" title="TITLE" href="https://bugs.eclipse.org/301314">301314</a></p></td> |
| <td><p>PARA</p> |
| </td> |
| </tr> |
| |
| |
| <tr><td colspan="2" id="releng"><h2>Release Engineering</h2></td></tr> |
| <tr> |
| <td><p align="right"><b>HEADING</b><br> |
| <span class="since">since 2.1M6</span><br> |
| <a class="buglink" title="TITLE" href="https://bugs.eclipse.org/301314">301314</a></p></td> |
| <td><p>PARA</p> |
| </td> |
| </tr> |
| --> |
| </table> |
| </body> |
