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Developing Persistence Architectures Using EclipseLink Database Web Services, Release 2.5
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Beta Draft: 2013-04-15

Using an EclipseLink SessionCustomizer

When using an EclipseLink SessionCustomizer with DBWS, you can access to the EclipseLink API to retrieve the OR (object-relational) or OX (object-XML) mapping descriptors from the session. You can then use the descriptors to add, change, or delete mappings.

For more information, see "Session Customization in the EclipseLink documentation:
http://wiki.eclipse.org/Introduction_to_EclipseLink_Sessions_%28ELUG%29#Session_Customization

Example

This example illustrates how to implement an EclipseLink SessionCustomizer:

package some.java.package;
 
import org.eclipse.persistence.config.SessionCustomizer; 
import org.eclipse.persistence.sessions.Session; 
import org.eclipse.persistence.sessions.DatabaseLogin; 
 
public class MySessionCustomizer implements SessionCustomizer {
 
  public MySessionCustomizer() {
  }
 
  public void customize(Sesssion session) { 
    DatabaseLogin login = (DatabaseLogin)session.getDatasourceLogin();
    // enable 'dirty' reads
    login.setTransactionIsolation(DatabaseLogin.TRANSACTION_READ_UNCOMMITTED); 
  } 
}
 

In the DBWSBuilder configuration file, you must use the orSessionCustomizerClassName or oxSessionCustomizerClassName to specify if the customization applies to the ORM or ORX project (respectively), as shown here:

Example 2-3 ORM Project

<?xml version="1.0" encoding="UTF-8"?> 
<dbws-builder xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
  <properties>
    <property name="projectName">customize_test</property>
     ...
    <property name="orSessionCustomizerClassName">some.java.package.MyORSessionCustomizer</property>
 

Example 2-4 ORX Project

<?xml version="1.0" encoding="UTF-8"?> 
<dbws-builder xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
  <properties>
    <property name="projectName">customize_test</property>
     ...
    <property name="oxSessionCustomizerClassName">some.java.package.MyOXSessionCustomizer</property>
 

Advanced Customization

You can further customize an EclipseLink DBWS service by creating your own EclipseLink project.xml and sessions.xml files. Using your preferred utility, you can:

  • map your objects to your relational database in an EclipseLink relational project

  • map your objects to your XML schema in an EclipseLink XML project

  • create an EclipseLink sessions.xml file that references both projects.

In this way, you can control all aspects of the relational and XML mapping. This approach is best when you want to customize most or all details.

In Example 2-5, a DBWS service is constructed from existing EclipseLink project maps with identical case-sensitive aliases (for Descriptors that are common between the projects).

Example 2-5 Sample DBWS Service

<?xml version="1.0" encoding="UTF-8"?>
<object-persistence version="Eclipse Persistence Services - some version (some build date)" xmlns="http://www.eclipse.org/eclipselink/xsds/persistence" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:eclipselink="http://www.eclipse.org/eclipselink/xsds/persistence">
   <name>SomeORProject</name>
   <class-mapping-descriptors>
      <class-mapping-descriptor xsi:type="relational-class-mapping-descriptor">
         <class>some.package.SomeClass</class>
         <alias>SomeAlias</alias>
...
 

<?xml version="1.0" encoding="UTF-8"?>
<object-persistence version="Eclipse Persistence Services - some version (some build date)" xmlns="http://www.eclipse.org/eclipselink/xsds/persistence" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:eclipselink="http://www.eclipse.org/eclipselink/xsds/persistence">
   <name>SomeOXProject</name>
   <class-mapping-descriptor xsi:type="xml-class-mapping-descriptor">
      <class>some.package.SomeClass</class>
      <alias>SomeAlias</alias>
...
 

NoteNote:

When building a DBWS web service in this way (that is, without the DBWSBuilder Utility) be sure to create all the necessary deployment artifacts.


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