根据sessionId获取Session对象

Servlet2.1之后不支持SessionContext里面getSession(String id)方法。

但是，我们可以通过HttpSessionListener监听器和全局静态map自己实现一个SessionContext。

MySessionContext.java:

public class MySessionContext {

private static HashMap mymap = new HashMap();

public static synchronized void AddSession(HttpSession session) {

if (session != null) {

mymap.put(session.getId(), session);

}

}

public static synchronized void DelSession(HttpSession session) {

if (session != null) {

mymap.remove(session.getId());

}

}

public static synchronized HttpSession getSession(String session_id) {

if (session_id == null)

return null;

return (HttpSession) mymap.get(session_id);

}

}

MySessionListener.java:

public class MySessionListener implements HttpSessionListener {

public void sessionCreated(HttpSessionEvent httpSessionEvent) {

MySessionContext.AddSession(httpSessionEvent.getSession());

}

public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {

HttpSession session = httpSessionEvent.getSession();

MySessionContext.DelSession(session);

}

}

web.xml添加一个监听器：

<listener>

<listener-class>listener.MySessionListener</listener-class>

</listener>

根据sessionId获取Session对象：

String sessionId = request.getParameter("sessionId");

HttpSession session = MySessionContext.getSession(sessionId);