Entity listener examples
You can write EntityListeners based on your requirements. Several example scripts follow.
EntityListeners example using annotations
The following example shows the life-cycle callback method invocations and order of the invocations. Assume an entity class Employee and two entity listeners exist: EmployeeListener and EmployeeListener2.@Entity
@EntityListeners({EmployeeListener.class, EmployeeListener2.class})
public class Employee {
@PrePersist
public void checkEmployeeID() {
....
}
}
public class EmployeeListener {
@PrePersist
public void onEmployeePrePersist(Employee e) {
....
}
}
public class PersonListener {
@PrePersist
public void onPersonPrePersist(Object person) {
....
}
}
public class EmployeeListener2 extends PersonListener {
@PrePersist
public void onEmployeePrePersist2(Object employee) {
....
}
}
If a PrePersist event occurs on an Employee instance,
the following methods are called in order:
- onEmployeePrePersist method
- onPersonPrePersist method
- onEmployeePrePersist2 method
- checkEmployeeID method
Entity listeners example using XML
The following example shows how to set an entity listener on an entity using the entity descriptor XML file:<entity
class-name="com.ibm.websphere.objectgrid.sample.Employee"
name="Employee" access="FIELD">
<attributes>
<id name="id" />
<basic name="value" />
</attributes>
<entity-listeners>
<entity-listener
class-name="com.ibm.websphere.objectgrid.sample.EmployeeListener">
<pre-persist method-name="onListenerPrePersist" />
<post-persist method-name="onListenerPostPersist" />
</entity-listener>
</entity-listeners>
<pre-persist method-name="checkEmployeeID" />
</entity>
The entity Employee is configured with a com.ibm.websphere.objectgrid.sample.EmployeeListener entity
listener class , which has two life-cycle callback methods defined.
The onListenerPrePersist method is for the PrePersist
event, and the onListenerPostPersist method is
for the PostPersist event. Also, the checkEmployeeID method
in the Employee class is configured to listen for the PrePersist event.