ginge

Spring, Springmodules, JBPM持久化集成理解系列三

public final void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
			throws ServletException, IOException;

protected void doFilterInternal(
			HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		//1，	先把SessionFactory取出来。
		SessionFactory sessionFactory = lookupSessionFactory(request);
		boolean participate = false;

		//2.1	如果是设置了isSingleSession为true，则整个request请求中都会只使用一个session。
		if (isSingleSession()) {
			// single session mode
			//2.2 再看看当前线程是不是已经存在一个可用的session
			if (TransactionSynchronizationManager.hasResource(sessionFactory)) {
				// Do not modify the Session: just set the participate flag.
				participate = true;
			}
			else {
				logger.debug("Opening single Hibernate Session in OpenSessionInViewFilter");
				//2.3	没有就创建一个
				Session session = getSession(sessionFactory);
				TransactionSynchronizationManager.bindResource(sessionFactory, new SessionHolder(session));
			}
		}
		else {
			// deferred close mode
			//3.1 如果已经延迟关闭策略已经被激活，则什么事情也不做
			if (SessionFactoryUtils.isDeferredCloseActive(sessionFactory)) {
				// Do not modify deferred close: just set the participate flag.
				participate = true;
			}
			else {
				//3.2  如果为false，则激活延迟关闭session策略
				SessionFactoryUtils.initDeferredClose(sessionFactory);
			}
		}

		try {
			filterChain.doFilter(request, response);
		}

		finally {
			//4.1，	filter返回后，如果在进入该filter之前延迟关闭已经被激活，该filter不负责关闭session，
			if (!participate) {
				if (isSingleSession()) {
					// single session mode
					SessionHolder sessionHolder =
							(SessionHolder) TransactionSynchronizationManager.unbindResource(sessionFactory);
					logger.debug("Closing single Hibernate Session in OpenSessionInViewFilter");
					closeSession(sessionHolder.getSession(), sessionFactory);
				}
				else {
					//4.2  如延迟关闭是该filter激活的，就在此关闭session
					// deferred close mode
					SessionFactoryUtils.processDeferredClose(sessionFactory);
				}
			}
		}
	}

SessionFactoryUtils.closeSessionOrRegisterDeferredClose(session, getSessionFactory());就像它字面要表达的，如果延迟关闭策略处于激活状态，则只是将session注册到一个容器里，到某个时刻再统一关闭，例如在OpenSessionInViewFilter返回时。