session同步

做过weblogic集群环境的人应该都清楚，要想实现session同步，必须满足两个条件：第一，在weblogic.xml里面增加session同步相关的代码；第二，所有放入session的类都要序列化。

    但是，我终于还是栽了。两个条件明明都满足了，但就是“有些”对象就是不能同步。经过5个小时的奋战，终于让我找到了问题所在。我称之为“第三个条件”。

    我以前使用session是这样的：

Customer customer = (Customer)session.getAttribute(KEY_CUSTOMER);
customer.setName("funcreal");

Customer customer = (Customer)session.getAttribute(KEY_CUSTOMER);
customer.setName("funcreal");

    这样写完以后，在单机环境下，session中的变量customer的name属性就被更改了。然而在集群环境下，仅仅这样做是不能触发session同步机制的。必须要把customer变量在重新放入session中，即：

session.setAttibute(KEY_CUSTOMER, customer);

session.setAttibute(KEY_CUSTOMER, customer);

   后来我从weblogic的售后工程师那里也确认了这一点。一点点经验，和大家分享。

 

在weblogic的文档中又翻出了以下内容，要是之前认真看了就好了：

Use setAttribute to Change Session State：
In an HTTP servlet that implements javax.servlet.http.HttpSession, use HttpSession.setAttribute (which replaces the deprecated putValue) to change attributes in a session object. If you set attributes in a session object with setAttribute, the object and its attributes are replicated in a cluster using in-memory replication. If you use other set methods to change objects within a session, WebLogic Server does not replicate those changes. Every time a change is made to an object that is in the session, setAttribute() should be called to update that object across the cluster.