Revision as of 08:43, 20 October 2009

Canonical model generation

JPA 2.0 Root | bug 267391

Discussion

Issue Summary

With the new Criteria API from the JPA 2.0 spec, EclipseLink will provide a way to produce static metamodel classes corresponding to the entities, mapped superclasses, and embeddable classes in the persistence unit. A static metamodel class models the persistent state and relationships of the corresponding managed class.

For portability, EclipseLink will generate the canonical metamodel as defined in section 6.2.1.1.

General solution

EclipseLink will employ the annotation processor tool (APT) in conjunction with its existing metadata processing of annotations and XML to generate the static metamodel classes.

For more information on APT, see: http://java.sun.com/j2se/1.5.0/docs/guide/apt/GettingStarted.html

Metadata processing

Configuring and using within Eclipse Galileo

The following steps outline how to configure the metamodel generation within the Eclipse IDE.

1. Select Project - Properties
2. Select Java Compiler and ensure you are using JDK 1.6+
3. Expand Java Compiler and select Annotation Processing.
4. On the right, select the checkbox Enable annotation processing
5. In the text box for Generated Source Directory enter the name of the directory to which you would like to generate the metamodel classes
6. By default, Processor options are not needed. However, EclipseLink provides you with custom generation options if you would like to configure you metamodel classes differently then defined in the spec. See section ?? for valid processor options that can be used.
7. Expand Annotation Processing and select Factory Path
   1. Here you must add three libraries/jars for the processor to work (see 1.2.0 RC4 Library names below):
      1. The eclipselink.jar
      2. The java persistence 2.0 preview jar
      3. A special jar containing an enabling services file that specifies the name of the annotation processor tool.

Configuring and using within ANT

EclipseLink custom processor options

1.2.0 RC4 Library names

Currently the target release of EclipseLink 1.2.0 is RC4 which uses the following jar files names in the ZIP installer. Please note that the ZIP installer is the only distribution of EclipseLink including the modelgen JAR file.

1. Services file (enables the processor).

\eclipselink\jlib\jpa\eclipselink-jpa-modelgen_1.2.0.v20091016-r5565.jar

1. javax.persistence library

\eclipselink\jlib\jpa\javax.persistence_2.0_preview.jar

1. EclipseLink jar

\eclipselink\jlib\eclipselink.jar

Troubleshooting

After following the configuration steps above if no classes are generated, check the following.

1. Ensure you have a persistence.xml. The default is META-INF/persistence.xml. If your persistence XML file is named differently or located elsewhere, you'll need to add the eclipselink.persistencexml processor option.

Work schedule

Future