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https://issues.apache.org/jira/browse/LUCENE-4808?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13590422#comment-13590422
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Uwe Schindler commented on LUCENE-4808:
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One note: Code that's already compiled and calling isAnnotationPresent() will
not break java, as the runtime is emulating default method calls in hotspot.
It's only javac with -source 1.6 that breaks. So if you download older Lucene
versions as binary and compile your code against it, e.g. SolrJ will still
work, although it calls this method. But You are no longer able to compile
Lucene/Solr with JDK8 -> and thats the regression.
> Add workaround for a JDK 8 "class library bug" which is still under
> discussion any may *not* be fixed
> -----------------------------------------------------------------------------------------------------
>
> Key: LUCENE-4808
> URL: https://issues.apache.org/jira/browse/LUCENE-4808
> Project: Lucene - Core
> Issue Type: Bug
> Components: general/build
> Affects Versions: 4.1, 5.0
> Reporter: Uwe Schindler
> Assignee: Uwe Schindler
>
> With JDK8 build 78 there was introduced a backwards compatibility regression
> which may not be fixed until release, because Oracle is possibly accepting
> this backwards break regarding cross-compilation to JDK6.
> The full thread on the OpenJDK mailing list:
> [http://mail.openjdk.java.net/pipermail/compiler-dev/2013-February/005737.html]
> (continues in next month:
> http://mail.openjdk.java.net/pipermail/compiler-dev/2013-March/005748.html)
> *In short:* JDK 8 adds so called default implementations on interfaces (means
> you can add a new method to an interface and provide a "default"
> implementation, so code implementing this interface is not required to
> implement the new method. This is really cool and would also help Lucene to
> make use of Interfaces instead of abstract classes which don't allow
> polymorphism).
> In Lucene we are still compatible with Java 7 and Java 6. So like millions of
> other open source projects, we use "-source 1.6 -target 1.6" to produce class
> files which are Java 1.6 conform, although you use a newer JDK to compile. Of
> course this approach has problem (e.g. if you use older new methods, not
> available in earliert JDKs). Because of this we must at least compile Lucene
> with a JDK 1.6 legacy JDK and also release the class files with this version.
> For 3.6, the RM has to also install JDK 1.5 (which makes it impossible to do
> this on Mac). So -source/-target is a alternative to at least produce 1.6/1.5
> compliant classes. According to Oracle, this is *not* the correct way to do
> this: Oracle says, you have to use: -source, -target and -Xbootclasspath to
> really crosscompile -> and the last thing is what breaks here. To correctly
> set the bootclasspath, you need to have an older JDK installed or you should
> be able to at least download it from maven (which is not available to my
> knowledge).
> The problem with JDK8 is now: If you compile with -source/-target but not the
> bootclasspath, it happens that the compiler does no longer understand new
> JDK8 class file structures in the new rt.jar, so producing compile failures.
> In the case of this bug: AnnotatedElement#isAnnotationPresent() exists since
> Java 1.5 in the interface, but all implementing classes have almost the same
> implementation: "return getAnnotation(..) != null;". So the designers of the
> class library decided to move that method as so called default method into
> the interface itsself, removing code duplication. If you then compile code
> with "-source 1.6 -target 1.6" using that method, the javac compier does not
> know about the new default method feature and simply says: "Method not found
> in java.lang.Class":
> {noformat}
> [javac] Compiling 113 source files to C:\Users\Uwe
> Schindler\Projects\lucene\trunk-lusolr3\lucene\build\test-framework\classes\java
> [javac] C:\Users\Uwe
> Schindler\Projects\lucene\trunk-lusolr3\lucene\test-framework\src\java\org\apache\lucene\util\TestRuleSetupAndRestoreClassEnv.java:134:
> error: cannot find symbol
> [javac] if (targetClass.isAnnotationPresent(SuppressCodecs.class)) {
> [javac] ^
> [javac] symbol: method isAnnotationPresent(Class<SuppressCodecs>)
> [javac] location: variable targetClass of type Class<?>
> [javac] Note: Some input files use or override a deprecated API.
> [javac] Note: Recompile with -Xlint:deprecation for details.
> [javac] 1 error
> {noformat}
> But until the Oracle people have a good workaround (I suggested to still
> implement the method on the implementation classes like Class/Method/... but
> delegate to the interface's default impl), we can quickly commit a
> replacement of this broken method call by (getAnnotation(..) != null). I want
> to do this, so we can enable jenkins builds with recent JDK 8 again.
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