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);