Java Data Objects

Deleting Instances

You can call one of the following PersistenceManager methods to delete one or more persistent instances from the datastore:

void deletePersistent(Object obj);
void deletePersistentAll(Object[] objs);
void deletePersistentAll(Collection objs);

They must be called in the context of an active transaction, or a JDOUserException is thrown. The representation of the instance in the datastore is deleted when it is flushed to the datastore (via commit( ) or evict( )). Chapter 13 covers the evict( ) method. These methods have no effect on instance parameters that are already deleted in the transaction. They throw a JDOUserException if a parameter is transient or managed by a different PersistenceManager.

The following application is used to delete a customer from the datastore. This includes deleting all the customer’s transactions. Line [1] accesses the Customer instance. If line [2] determines that Rental instances are still associated with the Customer instance, the application prints an error message and returns without removing any data. Otherwise, it deletes the Customer instance and its associated Address and Transaction instances.

package com.mediamania.store; import java.util.Set; import java.util.List; import com.mediamania.MediaManiaApp; public class DeleteCustomer extends MediaManiaApp { private String lastName; private String firstName; public DeleteCustomer(String fname, String lname) { lastName = lname; firstName = fname; } public static void main(String[] ...