zabbix应用之proxy分布式部署(2)

Spring, Springmodules, JBPM持久化集成--摆脱
LazyInitializationException(Part2)
Spring, Springmodules, JBPM持久化集成理解系列三
【本系列如需转载，请注明作者及出处】

到此，如果有朋友还是比较清醒的话，应该还会有疑问，在OpenSessionInViewFilter里如果是isSingleSession为true，并没有看到session的关闭，到底是在什么地方关闭了呢？它其实是在OpenSessionInViewInterceptor里关闭了的。

 

public void afterCompletion(WebRequest request, Exception ex) throws DataAccessException {
String participateAttributeName = getParticipateAttributeName();
Integer count = (Integer) request.getAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
if (count != null) {
// Do not modify the Session: just clear the marker.
if (count.intValue() > 1) {
request.setAttribute(participateAttributeName, new Integer(count.intValue() - 1), WebRequest.SCOPE_REQUEST);
}
else {
request.removeAttribute(participateAttributeName, WebRequest.SCOPE_REQUEST);
}
}
else {
if (isSingleSession()) {
// single session mode
SessionHolder sessionHolder =
(SessionHolder) TransactionSynchronizationManager.unbindResource(getSessionFactory());
logger.debug("Closing single Hibernate Session in OpenSessionInViewInterceptor");
SessionFactoryUtils.closeSession(sessionHolder.getSession());
}
else {
// deferred close mode
SessionFactoryUtils.processDeferredClose(getSessionFactory());
}
}
}

 
 
 
总结一下：OpenSessionInViewFilter首先会确保sessionFactory的存在，如果启用了session延迟关闭策略，也就是isSingleSession为false，session的创建和打开会在HibernateTemplate的execute里发生，而关闭会统一在OpenSessionInViewFilter返回时。  如果isSingleSession为true时，session的打开会在OpenSessionInViewFilter里或者之前的某个时候，而关闭会在OpenSessionInViewInterceptor里。  这样我们就可用自己在Junit或者其他应用场景使用延迟关闭策略来使我们的程序收益。以下附带前面篇章提及到的BaseTestCase，如果存在SessionFactory，则激活延迟关闭session策略。各位可用参考使用。 

package com.cabernet;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.FlushMode;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.orm.hibernate3.SessionFactoryUtils;
import org.springframework.orm.hibernate3.SessionHolder;
import org.springframework.test.AbstractDependencyInjectionSpringContextTests;
import org.springframework.transaction.support.TransactionSynchronizationManager;

/**
* Supports OpenSessionInViewFilter like Hibernate Lazy-loading when
* SessionFactory is present
*
* @author ginge
*
* @see OpenSessionInViewFilter
*/
public class BaseTestCase extends AbstractDependencyInjectionSpringContextTests
{
protected Log				log			= LogFactory.getLog(this.getClass());

private FlushMode			flushMode	= FlushMode.MANUAL;

protected SessionFactory	sessionFactory;

@Override
protected void prepareTestInstance() throws Exception
{
// TODO Auto-generated method stub
super.prepareTestInstance();

if (isSessionFactoryPresent())
{
afterSessionFactorySet();
SessionFactoryUtils.initDeferredClose(sessionFactory);
TransactionSynchronizationManager.bindResource(sessionFactory, new SessionHolder(this.getSession()));
}
}

@Override
protected void onTearDown() throws Exception
{
// TODO Auto-generated method stub

if (isSessionFactoryPresent())
{
SessionFactoryUtils.processDeferredClose(sessionFactory);
TransactionSynchronizationManager.unbindResource(sessionFactory);
}

super.onTearDown();
}

private boolean isSessionFactoryPresent()
{
return this.sessionFactory != null;
}

protected void afterSessionFactorySet()
{

}

public SessionFactory getSessionFactory()
{
return sessionFactory;
}

public void setSessionFactory(SessionFactory sessionFactory)
{
this.sessionFactory = sessionFactory;
}

@Override
protected String[] getConfigLocations()
{
return new String[] { "classpath*:applicationContext-resources.xml" };
}

protected Session getSession() throws DataAccessResourceFailureException
{
Session session = SessionFactoryUtils.getSession(sessionFactory, true);
FlushMode flushMode = getFlushMode();
if (flushMode != null)
{
session.setFlushMode(flushMode);
}
return session;
}

private FlushMode getFlushMode()
{
return this.flushMode;
}
}

 
 
 
 
到了这个时刻，我们回到Jbpm跟Springmodules, Spring的持久化集成上来，虽然Jbpm本身提供了JbpmContextFilter，它的功能是在Filter开始打开JbpmContext，Filter返回时关闭JbpmContext。但是在前面的篇章中，我们知道JbpmTemplate中会在操作开始前注入session。因此，使用了OpenSessionInViewFilter和JbpmTemplate之后，JbpmContextFilter将会英雄无用武之地。这个OpenSessionInViewFilter必须配置在其他Filter之前以确保在进入其他Filter之前激活延迟关闭策略或者绑定Session到当前线程中。
 
 
（完结）