/*
* Copyright 2002-2009 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.orm.jdo;
import javax.jdo.JDOException;
import javax.jdo.PersistenceManager;
/**
* Callback interface for JDO code. To be used with {@link JdoTemplate}'s
* execution methods, often as anonymous classes within a method implementation.
* A typical implementation will call PersistenceManager CRUD to perform
* some operations on persistent objects.
*
* <p>Note that JDO works on bytecode-modified Java objects, to be able to
* perform dirty detection on each modification of a persistent instance field.
* In contrast to Hibernate, using returned objects outside of an active
* PersistenceManager poses a problem: To be able to read and modify fields
* e.g. in a web GUI, one has to explicitly make the instances "transient".
* Reassociation with a new PersistenceManager, e.g. for updates when coming
* back from the GUI, isn't possible, as the JDO instances have lost their
* identity when turned transient. This means that either value objects have
* to be used as parameters, or the contents of the outside-modified instance
* have to be copied to a freshly loaded active instance on reassociation.
*
* @author Juergen Hoeller
* @since 03.06.2003
* @see JdoTemplate
* @see JdoTransactionManager
*/
public interface JdoCallback<T> {
/**
* Gets called by <code>JdoTemplate.execute</code> with an active JDO
* <code>PersistenceManager</code>. Does not need to care about activating
* or closing the <code>PersistenceManager</code>, or handling transactions.
*
* <p>Note that JDO callback code will not flush any modifications to the
* database if not executed within a transaction. Thus, you need to make
* sure that JdoTransactionManager has initiated a JDO transaction when
* the callback gets called, at least if you want to write to the database.
*
* <p>Allows for returning a result object created within the callback,
* i.e. a domain object or a collection of domain objects.
* A thrown custom RuntimeException is treated as an application exception:
* It gets propagated to the caller of the template.
*
* @param pm active PersistenceManager
* @return a result object, or <code>null</code> if none
* @throws JDOException if thrown by the JDO API
* @see JdoTemplate#execute
* @see JdoTemplate#executeFind
*/
T doInJdo(PersistenceManager pm) throws JDOException;
}
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