org.springframework.orm.toplink.SessionReadCallback Maven / Gradle / Ivy
/*
* Copyright 2002-2005 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;
import oracle.toplink.sessions.UnitOfWork;
/**
* Convenient abstract implementation of the TopLinkCallback interface,
* exposing either the plain TopLink Session or the TopLink UnitOfWork
* (which extends the Session interface) to code that reads persistent objects.
*
* Exposes the UnitOfWork if there is an active one (that is, if we're running
* within a non-read-only transaction); else exposes the Session itself.
* This allows to modify returned objects within a transaction, which is
* often desired, while the same code will return shared cache objects
* if running outside a transaction.
*
*
If "enforceReadOnly" is demanded, the callback will always expose the
* Session itself, avoiding the UnitOfWork overhead in any case.
*
* @author Juergen Hoeller
* @since 1.2
* @see oracle.toplink.sessions.Session#getActiveUnitOfWork()
* @see #readFromSession(oracle.toplink.sessions.Session)
*/
public abstract class SessionReadCallback implements TopLinkCallback {
private final boolean enforceReadOnly;
/**
* Create a new SessionReadCallback, not enforcing read-only objects.
*/
public SessionReadCallback() {
this.enforceReadOnly = false;
}
/**
* Create a new SessionReadCallback, enforcing read-only objects if demanded.
* @param enforceReadOnly whether to enforce returning read-only objects,
* even if running within a non-read-only transaction
*/
public SessionReadCallback(boolean enforceReadOnly) {
this.enforceReadOnly = enforceReadOnly;
}
/**
* Determines the Session to work on (either the active UnitOfWork
* or the plain Session) and delegates to readFromSession.
* @see #readFromSession(oracle.toplink.sessions.Session)
*/
public final Object doInTopLink(Session session) throws TopLinkException {
Session sessionToUse = session;
if (!this.enforceReadOnly) {
UnitOfWork unitOfWork = session.getActiveUnitOfWork();
if (unitOfWork != null) {
sessionToUse = unitOfWork;
}
}
return readFromSession(sessionToUse);
}
/**
* Called with a Session to work on, either the active UnitOfWork
* or the plain Session (as determined by the transaction status).
* @param session the TopLink Session to perform read operations on
* @return a result object, or null if none
* @throws TopLinkException in case of TopLink errors
*/
protected abstract Object readFromSession(Session session) throws TopLinkException;
}