Generate the JPA metamodel files using maven-processor-plugin - What is a convenient way for re-generation?

March 2018 Answer with Hibernate 5

As described on https://docs.jboss.org/hibernate/orm/5.0/topical/html/metamodelgen/MetamodelGenerator.html:

Simply add this to <project> <dependencies> ... </dependencies> </project> in your pom.xml:

<!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-jpamodelgen -->
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-jpamodelgen</artifactId>
    <version>5.2.16.Final</version>
    <scope>provided</scope>
</dependency>

There is nothing else that should be necessary for you to do. If you run into issues, visit the jboss page at the top of this answer.

The version included in this snippet is the latest version as of March, 2018, but check the artifact page (https://mvnrepository.com/artifact/org.hibernate/hibernate-jpamodelgen) for the latest version.

This is not intended to be an original answer, but should prove helpful to anyone who wants a simple, straightforward copy-pastable solution.

The proper solution is that generated sources should be in the target folder and shouldn't be put into the source-folders nor your SCM system.

Of course, by putting your generated sources into target, you would face the problem within your IDE because the related code can't be found. Therefore you can add the build-helper-maven-plugin to dynamically add the folder from the target directory.

<plugin>
    <groupId>org.bsc.maven</groupId>
    <artifactId>maven-processor-plugin</artifactId>
    <executions>
        <execution>
            <id>process</id>
            <goals>
                <goal>process</goal>
            </goals>
            <phase>generate-sources</phase>
            <configuration>
                <!-- source output directory -->
                <outputDirectory>${project.build.directory}/generated-sources/java/jpametamodel</outputDirectory>
                <processors>
                    <processor>org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor</processor>
                </processors>
                <overwrite>true</overwrite>
            </configuration>
        </execution>
    </executions>
</plugin>
<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>build-helper-maven-plugin</artifactId>
    <executions>
        <execution>
            <id>add-source</id>
            <phase>generate-sources</phase>
            <goals>
                <goal>add-source</goal>
            </goals>
            <configuration>
                <sources>
                    <source>${project.build.directory}/generated-sources/java/jpametamodel</source>
                </sources>
            </configuration>
        </execution>
    </executions>
 </plugin>

i have also a working solution and i want to share this one with others. so i hope that is the correct place for this.

the code can be found at GitHub https://github.com/StefanHeimberg/jpa21-maven-metagen

features:

• JPA 2.1
• Example with Hibernate Metamodel Generator
• Example with EclipseLink Metamodel Generator
• Minimal Maven configuration for IntelliJ (Tested with 14.1.4) and NetBeans (Tested with 8.1)
• M2E Workaround for Eclipse (Tested with 4.5.1) (Automatic profile activation)

pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.github.stefanheimberg</groupId>
    <artifactId>jpa21-maven-metagen</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

    <profiles>
        <profile>
            <id>hibernate</id>
            <activation>
                <activeByDefault>true</activeByDefault>
            </activation>
            <properties>
                <hibernate.version>5.0.3.Final</hibernate.version>
            </properties>
            <dependencies>
                <dependency>
                    <groupId>org.hibernate</groupId>
                    <artifactId>hibernate-jpamodelgen</artifactId>
                    <version>${hibernate.version}</version>
                    <scope>provided</scope>
                </dependency>
            </dependencies>
        </profile>

        <profile>
            <id>eclipselink</id>
            <activation>
                <activeByDefault>false</activeByDefault>
            </activation>
            <properties>
                <eclipselink.version>2.6.1</eclipselink.version>
            </properties>
            <dependencies>
                <dependency>
                    <groupId>org.eclipse.persistence</groupId>
                    <artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
                    <version>${eclipselink.version}</version>
                    <scope>provided</scope>
                </dependency>
            </dependencies>
        </profile>

        <profile>
            <id>m2e</id>
            <activation>
                <property>
                    <name>m2e.version</name>
                </property>
            </activation>
            <build>
                <pluginManagement>
                    <plugins>
                        <!--This plugin's configuration is used to store Eclipse m2e settings 
                        only. It has no influence on the Maven build itself. -->
                        <plugin>
                            <groupId>org.eclipse.m2e</groupId>
                            <artifactId>lifecycle-mapping</artifactId>
                            <version>1.0.0</version>
                            <configuration>
                                <lifecycleMappingMetadata>
                                    <pluginExecutions>
                                        <pluginExecution>
                                            <pluginExecutionFilter>
                                                <groupId>
                                                    org.codehaus.mojo
                                                </groupId>
                                                <artifactId>
                                                    build-helper-maven-plugin
                                                </artifactId>
                                                <versionRange>
                                                    [1.9.1,)
                                                </versionRange>
                                                <goals>
                                                    <goal>add-source</goal>
                                                </goals>
                                            </pluginExecutionFilter>
                                            <action>
                                                <execute>
                                                    <runOnConfiguration>true</runOnConfiguration>
                                                    <runOnIncremental>true</runOnIncremental>
                                                </execute>
                                            </action>
                                        </pluginExecution>
                                    </pluginExecutions>
                                </lifecycleMappingMetadata>
                            </configuration>
                        </plugin>
                    </plugins>
                </pluginManagement>
                <plugins>
                    <plugin>
                        <groupId>org.codehaus.mojo</groupId>
                        <artifactId>build-helper-maven-plugin</artifactId>
                        <version>1.9.1</version>
                        <executions>
                            <execution>
                                <id>add-source</id>
                                <phase>generate-sources</phase>
                                <goals>
                                    <goal>add-source</goal>
                                </goals>
                                <configuration>
                                    <sources>
                                        <source>${project.build.directory}/generated-sources/annotations/</source>
                                    </sources>
                                </configuration>
                            </execution>
                        </executions>
                    </plugin>
                </plugins>
            </build>
        </profile>
    </profiles>
</project>