Java通过sessionId获取Session

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);