The OpenJPA distribution comes with a number of examples that illustrate the usage of various features.

This sample demonstrates how to combine JDO and JPA in a single application. The MachineMain.java program uses both EntityManagers and PersistenceManagers in a single transaction including persist, delete and query operations. The sample includes both annotated persistent classes as well as JDOR metadata information. The application can switch to either system simply by changing the bootstrap mechanism. Depending on which configuration system you use, OpenJPA will read the corresponding metadata format. You can override some or all of this behavior using OpenJPA's configuration options, such as openjpa.MetaDataFactory. To use this sample, you should ensure that either a jdo.properties or persistence.xml are in the META-INF directory in your CLASSPATH. The rest of the files for this sample are located in the samples/mixed directory of the OpenJPA installation. This tutorial requires JDK 5. To run this tutorial: Ensure that your environment is set properly as described in the README and that your current path is in the mixed sample directory. You may want to edit ConnectionURL to point to an absolute URL (e.g. C:/openjpa/mixed-sample-db) if using a file-based database like HSQL. Include the list of persistent classes in your configuration file. For JPA, you will want to add the following lines to persistence.xml before the <property> lines: <class>samples.mixed.Machine</class> <class>samples.mixed.Crane</class> <class>samples.mixed.Bulldozer</class> <class>samples.mixed.Operator</class> If you are using JDO, point the metadata factory at the .jdo resource containing your persistent classes: openjpa.MetaDataFactory: Resources=samples/mixed/package.jdo Compile the classes: javac *.java You should then proceed to pass in the configuration file you are using to the enhancer: java org.apache.openjpa.enhance.PCEnhancer -p persistence.xml Machine.java Crane.java Bulldozer.java Operator.java Similarly, you should pass in the same argument to org.apache.openjpa.jdbc.meta.MappingTool: java org.apache.openjpa.jdbc.meta.MappingTool -p persistence.xml -a buildSchema Machine.java Crane.java Bulldozer.java Operator.java or java org.apache.openjpa.jdbc.meta.MappingTool -p jdo.properties -a buildSchema Machine.java Crane.java Bulldozer.java Operator.java You can now run the sample application. The first argument is which operation you want the program to run. The second argument tells the application which bootstrap system to use: java samples.mixed.MachineMain <create | delete> <jdo | jpa>

The files for this sample are located in the samples/persistence/models/humres directory of the OpenJPA installation. This sample demonstrates the mapping of an example "Human Resources" schema. The following concepts are illustrated in this sample: Value Mappings One to One Mappings One to Many Mappings (with and without inverses)