How to generate JPA 2.0 metamodel?

问题

In the spirit of type safety associated with the CriteriaQuery JPA 2.0 also has an API to support Metamodel representation of entities.

Is anyone aware of a fully functional implementation of this API (to generate the Metamodel as opposed to creating the metamodel classes manually)? It would be awesome if someone also knows the steps for setting this up in Eclipse (I assume it\'s as simple as setting up an annotation processor, but you never know).

EDIT: Just stumbled across Hibernate JPA 2 Metamodel Generator . But the issue remains since I can\'t find any download links for the jar.

EDIT 2: Awhile has passed since I asked this question, but I thought I\'d come back and add a link to the Hibernate JPA Model Generator project on SourceForge

回答1:

It would be awesome if someone also knows the steps for setting this up in Eclipse (I assume it's as simple as setting up an annotation processor, but you never know)

Yes it is. Here are the implementations and instructions for the various JPA 2.0 implementations:

EclipseLink

org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor

Hibernate

org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor
http://in.relation.to/2009/11/09/hibernate-static-metamodel-generator-annotation-processor

OpenJPA

org.apache.openjpa.persistence.meta.AnnotationProcessor6
http://openjpa.apache.org/builds/2.4.1/apache-openjpa/docs/ch13s04.html

DataNucleus

org.datanucleus.jpa.JPACriteriaProcessor
http://www.datanucleus.org/products/accessplatform_2_1/jpa/jpql_criteria_metamodel.html

The latest Hibernate implementation is available at:

https://mvnrepository.com/artifact/org.hibernate/hibernate-jpamodelgen/

An older Hibernate implementation is at:

http://repository.jboss.com/maven2/org/hibernate/hibernate-jpamodelgen/1.0.0.Final/hibernate-jpamodelgen-1.0.0.Final.jar

回答2:

Please take a look at jpa-metamodels-with-maven-example.

Hibernate

We need org.hibernate.org:hibernate-jpamodelgen.
The processor class is org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor.

Hibernate as a dependency

    <dependency>
      <groupId>org.hibernate.orm</groupId>
      <artifactId>hibernate-jpamodelgen</artifactId>
      <version>${version.hibernate-jpamodelgen}</version>
      <scope>provided</scope>
    </dependency>

Hibernate as a processor

      <plugin>
        <groupId>org.bsc.maven</groupId>
        <artifactId>maven-processor-plugin</artifactId>
        <executions>
          <execution>
            <goals>
              <goal>process</goal>
            </goals>
            <phase>generate-sources</phase>
            <configuration>
              <compilerArguments>-AaddGeneratedAnnotation=false</compilerArguments> <!-- suppress java.annotation -->
              <processors>
                <processor>org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor</processor>
              </processors>
            </configuration>
          </execution>
        </executions>
        <dependencies>
          <dependency>
            <groupId>org.hibernate.orm</groupId>
            <artifactId>hibernate-jpamodelgen</artifactId>
            <version>${version.hibernate-jpamodelgen}</version>
          </dependency>
        </dependencies>
      </plugin>

OpenJPA

We need org.apache.openjpa:openjpa.
The processor class is org.apache.openjpa.persistence.meta.AnnotationProcessor6.
OpenJPA seems require additional element <openjpa.metamodel>true<openjpa.metamodel>.

OpenJPA as a dependency

  <dependencies>
    <dependency>
      <groupId>org.apache.openjpa</groupId>
      <artifactId>openjpa</artifactId>
      <scope>provided</scope>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <compilerArgs>
            <arg>-Aopenjpa.metamodel=true</arg>
          </compilerArgs>
        </configuration>
      </plugin>
    </plugins>
  </build>

OpenJPA as a processor

      <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>
              <processors>
                <processor>org.apache.openjpa.persistence.meta.AnnotationProcessor6</processor>
              </processors>
              <optionMap>
                <openjpa.metamodel>true</openjpa.metamodel>
              </optionMap>
            </configuration>
          </execution>
        </executions>
        <dependencies>
          <dependency>
            <groupId>org.apache.openjpa</groupId>
            <artifactId>openjpa</artifactId>
            <version>${version.openjpa}</version>
          </dependency>
        </dependencies>
      </plugin>

EclipseLink

We need org.eclipse.persistence:org.eclipse.persistence.jpa.modelgen.processor.
The processor class is org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor.
EclipseLink requires persistence.xml.

EclipseLink as a dependency

  <dependencies>
    <dependency>
      <groupId>org.eclipse.persistence</groupId>
      <artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
      <scope>provided</scope>
    </dependency>

EclipseLink as a processor

    <plugins>
      <plugin>
        <groupId>org.bsc.maven</groupId>
        <artifactId>maven-processor-plugin</artifactId>
        <executions>
          <execution>
            <goals>
              <goal>process</goal>
            </goals>
            <phase>generate-sources</phase>
            <configuration>
              <processors>
                <processor>org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor</processor>
              </processors>
              <compilerArguments>-Aeclipselink.persistencexml=src/main/resources-${environment.id}/META-INF/persistence.xml</compilerArguments>
            </configuration>
          </execution>
        </executions>
        <dependencies>
          <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
            <version>${version.eclipselink}</version>
          </dependency>
        </dependencies>
      </plugin>

DataNucleus

We need org.datanucleus:datanucleus-jpa-query.
The processor class is org.datanucleus.jpa.query.JPACriteriaProcessor.

DataNucleus as a dependency

  <dependencies>
    <dependency>
      <groupId>org.datanucleus</groupId>
      <artifactId>datanucleus-jpa-query</artifactId>
      <scope>provided</scope>
    </dependency>
  </dependencies>

DataNucleus as a processor

      <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>
              <processors>
                <processor>org.datanucleus.jpa.query.JPACriteriaProcessor</processor>
              </processors>
            </configuration>
          </execution>
        </executions>
        <dependencies>
          <dependency>
            <groupId>org.datanucleus</groupId>
            <artifactId>datanucleus-jpa-query</artifactId>
            <version>${version.datanucleus}</version>
          </dependency>
        </dependencies>
      </plugin>

回答3:

Eclipse's JPA 2.0 support through Dali (which is included in "Eclipse IDE for JEE Developers") has its own metamodel generator integrated with Eclipse.

Select your project in the Package Explorer
Go to Properties -> JPA dialog
Select source folder from Canonical metamodel (JPA 2.0) group
Click Apply button to generate metamodel classes in the selected source folder

This should work on any JPA provider as the generated classes are standard.

Also see here.

回答4:

For eclipselink, only the following dependency is sufficient to generate metamodel. Nothing else is needed.

    <dependency>
        <groupId>org.eclipse.persistence</groupId>
        <artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
        <version>2.5.1</version>
        <scope>provided</scope>
    </dependency>

回答5:

For Hibernate as provider which is most common IMHO:

In case of build tools like Gradle, Maven you need to have Hibernate JPA 2 Metamodel Generator jar in the classpath and compiler level>=1.6 that is all you need build the project and metamodel will be generated automatically.

In case of IDE Eclipse 1. goto Project->Properties->Java Compiler->Annotation Processing and enable it. 2. Expand Annotation Processing->Factory Path-> Add External Jar add Hibernate JPA 2 Metamodel Generator jar check the newly added jar and say OK. Clean and Build done!

Link Hibernate JPA 2 Metamodel Generator jar link from maven repo https://mvnrepository.com/artifact/org.hibernate/hibernate-jpamodelgen

来源：https://stackoverflow.com/questions/3037593/how-to-generate-jpa-2-0-metamodel

标签

java

jpa

jpa-2.0

metamodel

annotation-processing