Network Deployment (Distributed operating systems), v8.0 > Develop and deploying applications > Develop EJB applications > Develop applications that use the Java Persistence API

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.

Attention: When you use these JPA command tools, run them from the $PROFILE_ROOT/bin directory, rather than from the WAS_HOME/bin directory to make sure that we have the latest version of the commands for your release level.

For this task, you must specify the com.ibm.ws.jpa.thinclient_8.0.0.jar stand-alone Java archive (JAR) file in your class path. This stand-alone JAR file is available from the installation images. The location of this file on the server installation image is ${ WAS_HOME}/runtimes/com.ibm.ws.jpa.thinclient_8.0.0.jar..

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 that are 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.

Procedure

1. Generate your entities classes.

   These are Plain Old Java Object (POJO) entities. Depending upon your development model, you 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 you use this approach, you are most likely concerned with creating the architecture of your object model and then writing your entity classes. These entity classes would eventually drive the creation of your database model. If you are using a top-down mapping of the object model to the relational model, develop the entity classes and then use OpenJPA functionality to generate the database tables that are based on the entity classes. The wsmapping tool would help with this approach.
   Bottom-up mapping
   You start with your data model, which are the database schemas, and then you work upwards to your entity classes. The wsreversemapping tool would help with this approach.
   Meet in the middle mapping
   Probably the most common development model. You have a combination of the data model and the object model partially complete. Depending on the goals and requirements, negotiate the relationships to resolve any differences. Both the wsmapping tool and the wsreversemapping tool would help with this approach.

   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 you would any Java class, unless you are using the Criteria API. If you are using the Criteria API, also generate the Criteria API metamodel classes by including the following option with the javac command:

   -Aopenjpa.metamodel=true
   

   The following are examples of how you use this option.

   (AIX) (Solaris)

   WAS_HOME/java/bin/javac
   -Aopenjpa.metamodel=true
   -classpath WAS_HOME/runtimes/com.ibm.ws.jpa.thinclient_8.0.0.jar
   mypackage/MyEntity.java
   
   

   (Windows)

   WAS_HOME\java\bin\javac
   -Aopenjpa.metamodel=true
   -classpath WAS_HOME\runtimes\com.ibm.ws.jpa.thinclient_8.0.0.jar
    mypackage\MyEntity.java
   
   

   For more information about using Criteria API and AnnotationProcessor6, refer to the Apache OpenJPA User Guide, Chapter 11: JPA Criteria and Chapter 4: Generation of Canonical Metamodel classes for AnnotationProcessor6 options and the information center topic, Criteria API.

3. Enhance the entity classes using the JPA enhancer tool, or specify the Java agent to perform dynamic enhancement at run time.

   • Use the wsenhancer tool. The enhancer post-processes the bytecode that is generated by the Java compiler and adds the fields and methods that are necessary to implement the persistence features. For example examples on how to use the wsenhancer tool, see the topic, wsenhancer command.
   • We can specify the Java agent mechanism to perform the dynamic enhancement at run time. For example, type the following at the command prompt:

     java -javaagent:${
     APP_CLIENT_ROOT}/runtimes/com.ibm.ws.jpa.thinclient_8.0.0.jar com.xyz.Main
     

     Attention: We can either run the wsenhancer tool or specify the javaagent command. You do not need to do both.

4. Optional: If you are not using the development model for bottom-up mapping, generate or update your database tables automatically or by using the wsmapping tool.
   • By default, the object-relational mapping does not occur automatically, but you can configure the application server to provide that mapping with the openjpa.jdbc.SynchronizeMappings property. This property 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:

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

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

   • To manually update or generate your 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 wsmapping tool, see the topic, wsmapping command.

5. Optional: If you are using 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.

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

6. Optional: If you are using application-managed identity, generate an application-managed identity class with the wsappid tool. When you 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:

<?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> 

What to do next

For more information about any of the commands, classes or other OpenJPA information, refer to the Apache OpenJPA User Guide.
Task overview: Storing and retrieving persistent data with the JPA API
Associate persistence providers and data sources
Task overview: IBM Optim pureQuery Runtime
Configure JDBC providers to use pureQuery to access DB2
Configure pureQuery to use multiple DB2 package collections
Configure JPA to work in the environment
Configure JDBC providers to use pureQuery to access Informix

Related

wsappid command
wsenhancer command
wsjpaversion command
wsmapping command
wsreversemapping command
wsschema command
Merge utility
Troubleshoot JPA applications
Assembly tools
Apache OpenJPA User Guide: JPA
Apache OpenJPA User Guide: JPA Criteria
Dali Java Persistence Tools

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