The first step in creating an application is to build the Java POJO class or classes, depending on the application that will be persisted to the database. Configuration; public class Manage Employee $java Manage Employee .......
Let us consider our Employee class with get XXX and set XXX methods to make it Java Beans compliant class.
Finally, we will create our application class with the main() method to run the application.
We will use this application to save few Employee's records and then we will apply CRUD operations on those records.
In addition Entity B would be managed by Entity Manager X due to 3.2.4 Spec 3.24 ===================== The semantics of the flush operation, applied to an entity X are as follows: Btw. So you agree with me that it is a BUG that Open JPA tries to INSERT the entity and throws an exception due to the duplicate key? The behavior is undefined if the same Java instance is made managed in more than one persistence context.
Now Entity B would be managed by Entity Manager Y due to the cascading behavior you cited. And I come to the conclusion, that the only way to interpret it, is that managed entities of the SAME persistence context are meant. The spec also spelled out the following; ================================= 3.2.8 Managed Instances It is the responsibility of the application to insure that an instance is managed in only a single persistence context.
A POJO (Plain Old Java Object) is a Java object that doesn't extend or implement some specialized classes and interfaces respectively required by the EJB framework. When you design a class to be persisted by Hibernate, it's important to provide Java Beans compliant code as well as one attribute which would work as index like id attribute in the Employee class.
This could be an object read through a different persistence context, or an object that was cloned or serialized. This is not an introduction to Hibernate and you should already know the basics of configuration, object-relational mapping and working with entity instances.For an introductory article to Hibernate, visit our tutorial on Hibernate 4 with Spring. We should also understand the history of Hibernate development that led to some partly duplicated API methods.• If X is a managed entity, it is ignored by the merge operation, however, the merge operation is cascaded to entities referenced by relationships from X if these relationships have been annotated with the cascade element value cascade=MERGE or cascade=ALL annotation. If you wants to merge changed content in A to a different persistence context, you may have to do: I am just pointing out that merge() is meant for merging DETACHED entity into a persistence context.==================== merge() is for "detached" entity only. Per Spec: ==================== 184.108.40.206 Merging Detached Entity State The merge operation allows for the propagation of state from detached entities onto persistent entities managed by the entity manager. If an entity is managed by the SAME persistence context, there is nothing to merge since the state of X is already maintained, hence the merge operation is ignored.