Develop JPA 2.x applications for a Java SE environment

Prepare persistence applications to test outside of the application server container in a Java SE environment.

When we use these JPA command tools, run them from the profile_root/bin directory, rather than from the app_server_root/bin directory to make sure that we have the latest version of the commands for your release level.

For this task, specify the com.ibm.ws.jpa-2.1.thinclient_9.0.jar stand-alone JAR file in the classpath for compiling with JPA 2.1 interfaces. To compile with JPA 2.0 interfaces, specify the com.ibm.ws.jpa-2.0.thinclient_9.0.jar in your class path. This stand-alone JAR file is available from the installation images. The location of these files on the server installation image is in the ${app_server_root}/runtimes/ directory.

Important: Java Persistence API (JPA) applications require different configuration techniques from applications that use container-managed persistence (CMP) or bean-managed persistence (BMP). They do not follow the typical deployment techniques associated with applications that implement CMP or BMP. In JPA applications, define a persistence unit and configure the appropriate properties in the persistence.xml file to ensure that the applications can run in a Java SE environment.

There are some considerations for running JPA applications in a Java SE environment:

• Resource injection is not available. Configure these services specifically or programmatically.

• The life cycle of the EntityManagerFactory and EntityManager are managed by the application. Applications control the creation, manipulation, and deletion of these constructs programmatically.

Tasks

1. Generate your entities classes.

   These are Plain Old Java Object (POJO) entities. Depending upon the development model, we might use some or all of the JPA tools:

   Top-down mapping

   You start from scratch with the entity definitions and the object-relational mappings, and then you derive the database schemas from that data. If we use this approach, we are most likely concerned with creating the architecture of our object model and then writing your entity classes. These entity classes would eventually drive the creation of our database model. If we are using a top-down mapping of the object model to the relational model, develop the entity classes and then use your persistence provider's functionality to generate the database tables that are based on the entity classes. The wsmapping tool would help with this approach when we use OpenJPA as your persistence provider.

   Bottom-up mapping

   You start with the data model, which are the database schemas, and then you work upwards to your entity classes. The wsreversemapping tool would help with this approach when we use OpenJPA as your persistence provider.

   Meet in the middle mapping

   Probably the most common development model. We have a combination of the data model and the object model partially complete. Depending on the goals and requirements, we must negotiate the relationships to resolve any differences. Both the wsmapping tool and the wsreversemapping tool would help with this approach when we use OpenJPA as your persistence provider.

   The JPA solution for the application server provides several tools that help with developing JPA applications. Combining these tools with IBM Rational Application Developer provides a solid development environment for either Java EE or Java SE applications. Rational Application Developer includes GUI tools to insert annotations, a customizedpersistence.xml file editor, a database explorer, and other features. Another alternative is the Eclipse Dali project. More information about Rational Application Developer or the Eclipse Dali plug-in can be found at their respective websites.

2. Compile the entity classes.

   Compile the entities as we would any Java class, unless we are using the Criteria API. If we are using the Criteria API, we must also generate the Criteria API metamodel classes.

   The following are examples of how we use this option.

   Use EclipseLink, provide the following arguments with the javac command:

   -processor 
   org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor 
   -Aeclipselink.persistencexml= persistence.xml_location 
   

   app_server_root/java/bin/javac 
   -classpath app_server_root/runtimes/com.ibm.ws.jpa-2.1.thinclient_9.0.0.jar 
   -processor
   org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor 
   -Aeclipselink.persistencexml=app_location/src/META-INF/persistence.xml mypackage\MyEntity.java 
   

   Use OpenJPA or WSJPA, provide the following arguments with the javac command:

   -Aopenjpa.metamodel=true 
   

   app_server_root/java/bin/javac 
   -Aopenjpa.metamodel=true 
   -classpath app_server_root/runtimes/com.ibm.ws.jpa-2.0.thinclient_9.0.0.jar  
   mypackage/MyEntity.java 
   

3. Enhance the entity classes using the JPA enhancer tool, or specify the Java agent to perform dynamic enhancement at run time.
   • Use the eclenhancer tool for EclipseLink or use wsenhancer tool for OpenJPA.

     The enhancer post-processes the bytecode generated by the Java compiler and adds the fields and methods necessary to implement the persistence features. For examples on how to use the eclenhancer tool, see the eclenhancer command topic. For examples on how to use the wsenhancer tool, see the wsenhancer command topic.

   • We can specify the Java agent mechanism to perform the dynamic enhancement at run time. For example, type the following at the command prompt:

     For EclipseLink:

     java -javaagent:${app_client_root}/runtimes/com.ibm.ws.jpa-2.1.thinclient_9.0.jar com.xyz.Main  
     

     For OpenJPA:

     java -javaagent:${app_client_root}/runtimes/com.ibm.ws.jpa-2.0.thinclient_9.0.jar com.xyz.Main  
     

     We can either run an enhancer tool or specify the javaagent command. We do not need to do both.

4. Optional: If we are not using the development model for bottom-up mapping, generate or update our database tables automatically or using the eclenhancer tool or the wsmapping tool.
   • By default, the object-relational mapping does not occur automatically, but we can configure the application server to provide that mapping with the eclipselink.ddl-generation property for EclipseLink, or the openjpa.jdbc.SynchronizeMappings property For OpenJPA. These properties can accelerate development by automatically ensuring that the database tables match the object model. To enable automatic mapping, include the following line in the persistence.xml file:

     For EclipseLink:

     <property name="eclipselink.ddl-generation" value="create-tables"/>  
     

     For Open JPA:

     <property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)"/> 
     

     JPA 2.1 standard:

     <property name="javax.persistence.schema-generation.database.action" value="create"/> 
     

     To enable automatic object-relational mapping at run time, all of our persistent classes must be listed in the Java .class file, mapping file, and JAR file elements in XML format.

   • To manually update or generate the database tables, run the JPA mapping tool for the application server from the command line to create the tables in the database. For examples on how to run the eclenhancer tool, see the eclenhancer command topic. For examples of how to use the wsmapping tool, see the wsmapping command topic.

5. Optional: If we are using OpenJPA and DB2 and want to use static Structured Query Language (SQL), run the wsdbgen command. To use the wsdbgen command, IBM Optim PureQuery Run time must be installed. The wsdbgen command creates the persistence_unit_name.pdqxml file under the same META-INF directory where your persistence.xml file is located. If we have multiple persistence units, the wsdbgen command must be run for each persistence unit.

   When multiple pdqxml files are referenced by an application, use the Merge utility to combine them into a single pdqxml file. Specify the combined pdqxml file as pureQueryXml property of pdqProperties. See the Merge utility documentation in the IBM Integrated Data Management information center.

   Applications that utilize JPA and are configured to run static SQL can experience various exceptions. These exceptions might occur with the wsdbgen command, which we can use to prepare the application, or when the application is running and calls a JPA method. To resolve this problem, complete the following:

   1. Install the program temporary fixes (PTF) for the iSeries JDBC Driver V5R4. Install PTF numbers SI32561 and SI32562. We can find the PTFs through the IBM System i Support: PTF Cover Letters website.

   2. If we use DB2 Universal Database for iSeries V6R1 or V5R3, visit the fix web site for the appropriate release.

   3. Install the required level of IBM Optim PureQuery Run time, which is Version 1.3.100 or later. See IBM Data Studio pureQuery Runtime website. Install the latest JCC drivers, which is Version 3.52.95 or later, with the fix for APAR PK65069. The latest JCC drivers are part of the IBM DB2 software package.

   4. For DB2 on a z/OS server, install PTF UK39204 for the V8 alternate driver or PTF UK39205 for V9, and install the fix for APAR PK67706.

   For examples on how to run this command, see the topic, wsdbgen command.

6. Optional: If we are using OpenJPA and application-managed identity, generate an application-managed identity class with the wsappid tool. When we use an application-managed identity, one or more of the fields must be an identity field. Use an identity class if your entity has multiple identity fields and at least one of the fields is related to another entity. The application-managed identity tool generates Java code that uses the identity class for any persistent type that implements application-managed identity.

   For examples on how to use the wsappid tool, see the topic wsappid command.

Example

The following is a sample persistence.xml file for the Java SE Environment:

For EclipseLink:

<?xml version="1.0" encoding="UTF-8"?>  
<persistence xmlns="http://java.sun.com/xml/ns/persistence"      
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.1"
     xsi:schemaLocation="http://java.sun.com/xml/ns/persistence         
          http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">          
     <persistence-unit name="TheWildZooPU" transaction-type="RESOURCE_LOCAL">
          <!-- additional Mapping file, in addition to orm.xml>
         <mapping-file>META-INF/JPAorm.xml</mapping-file>
          <class>com.company.bean.jpa.PersistebleObjectImpl</class>
          <class>com.company.bean.jpa.Animal</class>
          <class>com.company.bean.jpa.Dog</class>
          <class>com.company.bean.jpa.Cat</class>
          <properties>
             <property name="javax.persistence.jdbc.driver"
                        value="org.apache.derby.jdbc.EmbeddedDriver"/>
             <property name="javax.persistence.jdbc.url"
                       value="jdbc:derby:target/database/jpa-test-database;create=true" />
             <property name="javax.persistence.schema-generation.database.action"
                        value="create" />
             <property name="javax.persistence.jdbc.user"
                        value="user" />
             <property name="javax.persistence.jdbc.password"
                        value="password"/>
          </properties>
     </persistence-unit>
</persistence>
      

For OpenJPA:

<?xml version="1.0" encoding="UTF-8"?>  
<persistence xmlns="http://java.sun.com/xml/ns/persistence"               
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      version="2.0"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
                       http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
            <persistence-unit name="TheWildZooPU" transaction-type="RESOURCE_LOCAL">
              <!-- additional Mapping file, in addition to orm.xml>
              <mapping-file>META-INF/JPAorm.xml</mapping-file>
              <class>com.company.bean.jpa.PersistebleObjectImpl</class>
              <class>com.company.bean.jpa.Animal</class>
              <class>com.company.bean.jpa.Dog</class>
              <class>com.company.bean.jpa.Cat</class>
                   <properties>
                        <property name="openjpa.ConnectionDriverName"
                                value="org.apache.derby.jdbc.EmbeddedDriver" />
                        <property name="openjpa.ConnectionURL"
                                value="jdbc:derby:target/database/jpa-test-database;create=true" />
                        <property name="openjpa.Log"
                                value="DefaultLevel=INFO,SQL=TRACE,File=./dist/jpaEnhancerLog.log,Runtime=INFO,Tool=INFO" />
                        <property name="openjpa.ConnectionFactoryProperties"
                                value="PrettyPrint=true,PrettyPrintLineLength=72" />
                        <property name="openjpa.jdbc.SynchronizeMappings"
                                value="buildSchema(ForeignKeys=true)" />
                        <property name="openjpa.ConnectionUserName"
                                value="user" />
                        <property name="openjpa.ConnectionPassword"
                                value="password"/>
                        </properties>
            </persistence-unit>
</persistence>
    

Related:

Development and assembly tools

Task overview: Store and retrieve persistent data with the JPA API

Associating persistence providers and data sources

IBM Optim pureQuery Runtime

Configure JDBC providers to use pureQuery to access DB2

Configure pureQuery to use multiple DB2 package collections

Configure JDBC providers to use pureQuery to access Informix

Troubleshoot JPA applications

wsappid command

wsenhancer command

wsjpaversion command

wsmapping command

wsreversemapping command

wsschema command

Criteria API

Merge utility

Dali Java Persistence Tools