Future changes for JDK9

[Shredder121]

jdk9 label.

According to JEP 220, the new way of providing extra functionality is using 'modules'.
This means there will be no tools.jar, and there will probably have to be some changes regarding guiding users to solve having the tools on the classpath.

[schauder]

When building a project that uses this plugin with JDK, I get the following exception:

[INFO] --- apt-maven-plugin:1.1.3:process (default) @ spring-data-jpa-showcase ---

[ERROR] execute error
java.util.concurrent.ExecutionException: java.lang.RuntimeException: java.lang.NoClassDefFoundError: javax/annotation/Generated
at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
at com.mysema.maven.apt.AbstractProcessorMojo.execute(AbstractProcessorMojo.java:346)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:154)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:146)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:117)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:81)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:309)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:194)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:107)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:993)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:345)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:191)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:563)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: java.lang.RuntimeException: java.lang.NoClassDefFoundError: javax/annotation/Generated
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.handleExceptions(JavacTaskImpl.java:158)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.doCall(JavacTaskImpl.java:96)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:90)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:71)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1161)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: java.lang.NoClassDefFoundError: javax/annotation/Generated
at com.querydsl.codegen.EntitySerializer.introImports(EntitySerializer.java:423)
at com.querydsl.codegen.EntitySerializer.intro(EntitySerializer.java:269)
at com.querydsl.codegen.EntitySerializer.serialize(EntitySerializer.java:594)
at com.querydsl.apt.AbstractQuerydslProcessor.serialize(AbstractQuerydslProcessor.java:574)
at com.querydsl.apt.AbstractQuerydslProcessor.serializeMetaTypes(AbstractQuerydslProcessor.java:513)
at com.querydsl.apt.AbstractQuerydslProcessor.process(AbstractQuerydslProcessor.java:94)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:968)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(JavacProcessingEnvironment.java:884)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.access$2200(JavacProcessingEnvironment.java:108)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(JavacProcessingEnvironment.java:1206)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1315)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1246)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:922)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.lambda$doCall$0(JavacTaskImpl.java:100)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.handleExceptions(JavacTaskImpl.java:142)
... 7 more
Caused by: java.lang.ClassNotFoundException: javax.annotation.Generated
at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:466)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:553)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:486)
... 22 more

I was able to fix that with

export MAVEN_OPTS='--add-modules java.xml.ws.annotation'  

It would be nice to at least be able to specify that in the plugin configuration. See also: http://stackoverflow.com/a/43574427/66686