Generating QueryDSL classes with maven fails since 3.1.0

Question

When generating QueryDSL's Q... classes with the apt-maven-plugin the maven build fails with a NullPointerException in SimpleSerializerConfig - but only for maven versions since 3.1.0.

We already tried debugging into the maven build but that did not lead to any conclusions.

The maven configuration looks like this:

<plugin>
    <groupId>com.mysema.maven</groupId>
    <artifactId>apt-maven-plugin</artifactId>
    <version>1.1.1</version>
    <executions>
        <execution>
            <goals>
                <goal>process</goal>
            </goals>
            <configuration>
                <outputDirectory>target/generated-sources/java</outputDirectory>
                <processor>com.mysema.query.apt.jpa.JPAAnnotationProcessor</processor>
                <logOnlyOnError>true</logOnlyOnError>
            </configuration>
        </execution>
    </executions>
    <dependencies>
        <dependency>
            <groupId>com.mysema.querydsl</groupId>
            <artifactId>querydsl-apt</artifactId>
            <version>${querydsl.version}</version>
        </dependency>
        <dependency>
            <groupId>com.mysema.querydsl</groupId>
            <artifactId>querydsl-jpa</artifactId>
            <classifier>apt</classifier>
            <version>${querydsl.version}</version>
        </dependency>
    </dependencies>
</plugin>

with ${querydsl.version} being 2.9.0 - using a newer version does not fix the problem.

The exact stacktrace is

java.lang.RuntimeException: java.lang.NullPointerException
    at com.sun.tools.javac.main.Main.compile(Main.java:469)
    at com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:132)
    at com.mysema.maven.apt.AbstractProcessorMojo.execute(AbstractProcessorMojo.java:314)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:106)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:318)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:153)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:555)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:214)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:158)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:414)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:357)
Caused by: java.lang.NullPointerException
    at com.mysema.query.codegen.SimpleSerializerConfig.getConfig(SimpleSerializerConfig.java:29)
    at com.mysema.query.apt.DefaultConfiguration.<init>(DefaultConfiguration.java:129)
    at com.mysema.query.apt.jpa.JPAConfiguration.<init>(JPAConfiguration.java:69)
    at com.mysema.query.apt.jpa.JPAAnnotationProcessor.createConfiguration(JPAAnnotationProcessor.java:46)
    at com.mysema.query.apt.AbstractQuerydslProcessor.process(AbstractQuerydslProcessor.java:102)
    at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:793)
    at com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(JavacProcessingEnvironment.java:722)
    at com.sun.tools.javac.processing.JavacProcessingEnvironment.access$1700(JavacProcessingEnvironment.java:97)
    at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(JavacProcessingEnvironment.java:1029)
    at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1163)
    at com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1108)
    at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:824)
    at com.sun.tools.javac.main.Main.compile(Main.java:439)
    ... 23 more

Answer 1

This exception usually happens when there is a dependency conflict in the build. Try disabling the apt execution and see if there are other issues in the build.