Lazy-Loading Entities with Single-Valued Relationships

The JPA specification defines the EAGER and LAZY fetch types.

The SAP implementation of JPA supports lazy loading of single-valued and collection-valued relationships. For downward compatibility with releases prior to SAP NetWeaver 7.3, lazy loading of single-valued relationships must be enabled explicitly, as described below. Otherwise, such entities are loaded eagerly.

For more information about fetch types, refer to the Java Persistence API specification.

You have:

1. Created a project (for example, JPA, EJB, or Dynamic Web) to store the entities with the Java Persistence facet enabled

   For more information, see Creating JPA Projects in the Developer Studio .

2. Added the project containing your entities to an Enterprise Application (EAR) project

   For more information, see Assembling Components into Enterprise Applications .

Lazy loading of entities with single-valued relationships requires generation of proxy classes for the lazily loadable entities.

1. In the persistence.xml , enable generation of proxy classes.

                     <property name="com.sap.jpa.execution.generate-proxies" value="true" />
                  

2. In the application-j2ee-engine.xml , set a reference to the cglib_nodep_22 library.

                     <reference reference-type="hard">
           <reference-target provider-name="sap.com" target-type="library">cglib_nodep_22</reference-target>
   </reference>
                  

   For more information, see Editing the application-j2ee-engine.xml .

The EntityManager.getReference method now returns lazily loadable instances.