Eclipselink 2.5 Metamodel Generation using Maven - maven

Question

I would like to know how to generate static metamodels using Maven and Eclipselink 2.5. It worked fine by adding this lines to pom.xml when running Eclipselink 2.4.
// Generate meta model for eclipselink 2.4 (does not work for 2.5)
<plugin>
<groupId>org.bsc.maven</groupId>
<artifactId>maven-processor-plugin</artifactId>
<version>1.3.1</version>
<executions>
<execution>
<id>process</id>
<goals>
<goal>process</goal>
</goals>
<phase>generate-sources</phase>
<configuration>
<compilerArguments>-Aeclipselink.persistencexml=src/main/resources/META-INF/persistence.xml</compilerArguments>
<processors>
<processor>org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor</processor>
</processors>
<outputDirectory>${project.build.directory}/generated-sources/meta-model</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
But it seems like something has changed since 2.4 cause I get following error:
[INFO] javac option: -proc:only
[INFO] javac option: -Aeclipselink.persistencexml=src/main/resources/META-INF/persistence.xml
[INFO] javac option: -processor
[INFO] javac option: org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor
[INFO] javac option: -s
[INFO] javac option: /home/asdf/target/generated-sources/meta-model
[INFO] diagnostic error: Annotation processor 'org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor' not found
[INFO] diagnostic warning: Annotation processing without compilation requested but no processors were found.
[ERROR] execute error
java.lang.Exception: error during compilation
at org.bsc.maven.plugin.processor.AbstractAnnotationProcessorMojo.executeWithExceptionsHandled(AbstractAnnotationProcessorMojo.java:183)
at org.bsc.maven.plugin.processor.AbstractAnnotationProcessorMojo.execute(AbstractAnnotationProcessorMojo.java:96)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
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:320)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
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:409)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)
Can you guys out there help me? =)
B.R

Answer 1

It appears that they've moved the CanonicalModelProcessor class to it's own maven artifact:
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
<version>2.5.0</version>
</dependency>
The following maven-processor-plugin configuration works for me:
<plugin>
<groupId>org.bsc.maven</groupId>
<artifactId>maven-processor-plugin</artifactId>
<version>2.2.4</version>
<executions>
<execution>
<id>eclipselink-jpa-metamodel</id>
<goals>
<goal>process</goal>
</goals>
<phase>generate-sources</phase>
<configuration>
<processors>
<processor>org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor</processor>
</processors>
<outputDirectory>${project.build.directory}/generated-sources/meta-model</outputDirectory>
</configuration>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
<version>2.5.0</version>
<scope>provided</scope>
</dependency>
</dependencies>
</plugin>
Very important note: the metamodel is generated only if the entities are declared in the persistence unit. It doesn't work with discovered entities.

Answer 2

For me using maven-compiler-plugin from org.apache.maven.plugins resulted in MojoFailureException when using other command than mvn clean install.
The tested the solutions with org.eclipse.persistence.jpa.modelgen.processor 2.6.0.
The configuration in both cases is quite similar.
The main issue which I had with org.bsc.maven was to properly configure the compilerArguments parts. That is why I post (both) the solutions below.
The documentation is available: HERE.
Solution using maven-compiler-plugin from org.bsc.maven
For me this one worked better
<plugin>
<groupId>org.bsc.maven</groupId>
<artifactId>maven-processor-plugin</artifactId>
<executions>
<execution>
<id>eclipselink-jpa-metamodel</id>
<goals>
<goal>process</goal>
</goals>
<configuration>
<compilerArguments>
-Aeclipselink.persistencexml=${basedir}/src/main/resources/META-INF/persistence.xml
</compilerArguments>
<processors>
<processor>org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor
</processor>
</processors>
</configuration>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
<version>${eclipselink.version}</version>
<scope>compile</scope>
</dependency>
</dependencies>
</plugin>
Solution using maven-compiler-plugin from org.apache.maven.plugins
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
<version>${eclipselink.version}</version>
<scope>compile</scope>
</dependency>
...
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<compilerArgs>
<arg>-Aeclipselink.persistencexml=src/main/resources/META-INF/persistence.xml</arg>
</compilerArgs>
</configuration>
</plugin>

Answer 3

To make configuration a lot simpler I would recommend you test: https://github.com/ethlo/eclipselink-maven-plugin. You will not even be required to keep an updated persistence.xml file.
<plugin>
<groupId>com.ethlo.persistence.tools</groupId>
<artifactId>eclipselink-maven-plugin</artifactId>
<version>[version]</version>
<executions>
<execution>
<id>weave</id>
<phase>process-classes</phase>
<goals>
<goal>weave</goal>
</goals>
</execution>
<execution>
<id>modelgen</id>
<phase>generate-sources</phase>
<goals>
<goal>modelgen</goal>
</goals>
</execution>
</executions>
</plugin>
Note: I'm the author of the plugin.

Answer 4

2017 UPDATE:
Main answer to this question is now outdated.
You now need to perform the following steps in order to have it work.
1) Import the required dependency:
<!-- https://mvnrepository.com/artifact/org.eclipse.persistence/org.eclipse.persistence.jpa.modelgen.processor -->
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
<version>2.5.2</version>
<scope>compile</scope>
</dependency>
2) Specify persistence.xml location (this is a workaround for an EL bug. Please note that your path may vary from the one specified in this example):
<build>
<pluginManagement>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.5.1</version>
<executions>
<execution>
<id>default-compile</id>
<phase>compile</phase>
<goals>
<goal>compile</goal>
</goals>
</execution>
[...]
</executions>
<configuration>
<source>1.7</source>
<target>1.7</target>
<compilerArgs>
<arg>-Aeclipselink.persistencexml=src/main/resources/META-INF/persistence.xml</arg>
</compilerArgs>
</configuration>
</plugins>
[...]
</pluginManagement>
[...]
</build>
3) Finally refer to the following item in order to trigger the execution with Maven's new Lifecycle Mappings:
Usage of maven Build Helper Maven Plugin

Answer 5

you're likely to get the following error:
java.lang.RuntimeException: java.lang.SecurityException: class "org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProperties"'s signer information does not match signer information of other classes in the same package
Because of the unresolved bug compilation is broken, modelgen jar is signed in maven repository, the version must be set to 2.5.0-SNAPSHOT for now.

Answer 6

This is what I used
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>javax.persistence</artifactId>
<version>2.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>eclipselink</artifactId>
<version>2.5.1</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
<version>2.5.1</version>
<scope>provided</scope>
</dependency>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
<compilerArguments>
<endorseddirs>${endorsed.dir}</endorseddirs>
</compilerArguments>
</configuration>
<executions>
<execution>
<id>generate-entity-metamodel</id>
<phase>generate-sources</phase>
<goals>
<goal>
compile
</goal>
</goals>
<configuration>
<source>1.6</source>
<target>1.6</target>
<optimize>true</optimize>
<showDeprecation>true</showDeprecation>
<showWarnings>true</showWarnings>
<proc>only</proc>
<!--<compilerArgument>-Aeclipselink.metamodel=true</compilerArgument>
<generatedSourcesDirectory>${basedir}/src/main/java</generatedSourcesDirectory>-->
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>1.8</version>
<executions>
<execution>
<id>add-modelgen-generated-sources-directory</id>
<phase>generate-sources</phase>
<goals>
<goal>add-source</goal>
</goals>
<configuration>
<sources>
<source>${project.build.directory}/target/generated-sources/annotations</source>
</sources>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
the add-sources part is for netbeans 8 to understand it to put it in classpath
:)