Use JPA with Maven projects in Eclipse

Want to build your own metamodel in Eclipse?

Prerequisite: use EclipseLink
Add the following to your pom.xml file:

        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>eclipselink</artifactId>
            <version>2.5.1</version>
            <scope>provided</scope>
        </dependency>

First step: Modify your pom.xml file
The pom.xml file has to be modified to include the following plugin:

            <plugin>
                <groupId>org.bsc.maven</groupId>
                <artifactId>maven-processor-plugin</artifactId>
                <version>2.2.4</version>
                <executions>
                    <execution>
                        <id>process</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>2.6.1</version>
                    </dependency>
                </dependencies>
            </plugin>

Second step: add the Generated-sources folder
Then, open the project properties and move to Java Build Path. In the "Source" tab, select "Add folder" and then add "target/generated-sources".
Build the project.

Third step: compile
Finally, again in project properties, select the JPA menu, select EclipseLink as a platform, allow Discover annotated classes automatically, and then press Apply. From this point on, the generated-sources folder should contain your compiled metamodel.