/*
* Copyright 2002-2006 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.toplink;
import oracle.toplink.exceptions.TopLinkException;
import oracle.toplink.sessions.Session;
/**
* Callback interface for TopLink code. To be used with {@link TopLinkTemplate}'s
* execution methods, often as anonymous classes within a method implementation.
* A typical implementation will call TopLink Session CRUD to perform some
* operations on persistent objects.
*
* <p>The <code>Session</code> that gets passed into the <code>doInTopLink</code> method
* is usually a thread-safe <code>ClientSession</code>. Since this provides access to the
* TopLink shared cache, it is possible for implementations of this interface to return
* references to <i>read-only objects from the shared cache</i>. These objects
* <i>must not be modified</i> by application code outside of the DAO layer.
* If persistent objects need to be edited, they should be loaded from (or registered with)
* a TopLink UnitOfWork, or they should be explicitly copied and merged back into a
* <code>UnitOfWork</code> at a later point of time.
*
* <p>Users can access a <code>UnitOfWork</code> by using the <code>getActiveUnitOfWork</code>
* method on the <code>Session</code>. Normally, this will only be done when there is an
* active non-read-only transaction being managed by Spring's {@link TopLinkTransactionManager}
* or by an external transaction controller (usually a J2EE server's JTA provider,
* configured in TopLink). The <code>getActiveUnitOfWork</code> method will return
* <code>null</code> outside of a managed transaction.
*
* @author Juergen Hoeller
* @author <a href="mailto:@james.x.clark@oracle.com">James Clark</a>
* @see TopLinkTemplate
* @see TopLinkTransactionManager
*/
public interface TopLinkCallback {
/**
* Gets called by <code>TopLinkTemplate.execute</code> with an active
* <code>Session</code>. Does not need to care about activating or closing
* the TopLink <code>Session</code>, or handling transactions.
*
* <p>Note that write operations should usually be performed on the active
* <code>UnitOfWork</code> within an externally controlled transaction, through
* calling <code>getActiveUnitOfWork</code>. However, an implementation can also
* choose to use <code>acquireUnitOfWork</code> to create an independent
* <code>UnitOfWork</code>, which it needs to commit at the end of the operation.
*
* <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 session active TopLink Session
* @return a result object, or <code>null</code> if none
* @throws TopLinkException if thrown by the TopLink API
* @see oracle.toplink.sessions.Session#getActiveUnitOfWork()
* @see oracle.toplink.sessions.Session#acquireUnitOfWork()
* @see TopLinkTemplate#execute
* @see TopLinkTemplate#executeFind
*/
Object doInTopLink(Session session) throws TopLinkException;
}