tomcat共享多个web应用会话的实现方法


            tomcat共享多个web应用会话的实现方法

问题

今天有位朋友问了个问题，大致是：tomcat下两个Java web，一个是商城，一个是直播，从商城登录后，再跳转到直播，发现处于非登录状态。

解决思路



  将session抽出来成一个session服务，统一通过该服务操作session。

  tomcat内部用会话管理器获取会话时遍历所有context内的会话。

  



方案1

重写获取session方法即可。

方案2

找了源码发现已经支持类似遍历所有context内的会话的形式，首先获取session时，如果cressContext属性为true，则会在获取不到时尝试遍历所有context是否存在该sessionid，如果存在则在本context根据sessionid创建自己的session对象。





 public HttpSession getSession(boolean create) {



    if (crossContext) {



      // There cannot be a session if no context has been assigned yet

      if (context == null)

        return (null);



      // Return the current session if it exists and is valid

      if (session != null && session.isValid()) {

        return (session.getSession());

      }



      HttpSession other = super.getSession(false);

      if (create && (other == null)) {

        // First create a session in the first context: the problem is

        // that the top level request is the only one which can 

        // create the cookie safely

        other = super.getSession(true);

      }

      if (other != null) {

        Session localSession = null;

        try {

          localSession =

            context.getManager().findSession(other.getId());

          if (localSession != null && !localSession.isValid()) {

            localSession = null;

          }

        } catch (IOException e) {

          // Ignore

        }

        if (localSession == null && create) {

          localSession = 

            context.getManager().createSession(other.getId());

        }

        if (localSession != null) {

          localSession.access();

          session = localSession;

          return session.getSession();

        }

      }

      return null;



    } else {

      return super.getSession(create);

    }



  }







context（web应用）获取跨应用session时通过类似下面操作获取：





request.getSession().getServletContext().getContext("/app2").getAttribute("att2"); 



这是因为request会根据cookies的sessionid获取到session对象，这时不会报找不到，因为前面已经根据其他sessionid创建了一个session对象，然后getContext操作会获取对应url的context，接着进行会话操作。





public ServletContext getContext(String uri) {



    // Validate the format of the specified argument

    if (uri == null || !uri.startsWith("/")) {

      return null;

    }



    Context child = null;

    try {

      // Look for an exact match

      Container host = context.getParent();

      child = (Context) host.findChild(uri);



      // Non-running contexts should be ignored.

      if (child != null && !child.getState().isAvailable()) {

        child = null;

      }



      // Remove any version information and use the mapper

      if (child == null) {

        int i = uri.indexOf("##");

        if (i > -1) {

          uri = uri.substring(0, i);

        }

        // Note: This could be more efficient with a dedicated Mapper

        //    method but such an implementation would require some

        //    refactoring of the Mapper to avoid copy/paste of

        //    existing code.

        MessageBytes hostMB = MessageBytes.newInstance();

        hostMB.setString(host.getName());



        MessageBytes pathMB = MessageBytes.newInstance();

        pathMB.setString(uri);



        MappingData mappingData = new MappingData();

        ((Engine) host.getParent()).getService().findConnectors()[0].getMapper().map(

            hostMB, pathMB, null, mappingData);

        child = (Context) mappingData.context;

      }

    } catch (Throwable t) {

      ExceptionUtils.handleThrowable(t);

      return null;

    }



    if (child == null) {

      return null;

    }



    if (context.getCrossContext()) {

      // If crossContext is enabled, can always return the context

      return child.getServletContext();

    } else if (child == context) {

      // Can still return the current context

      return context.getServletContext();

    } else {

      // Nothing to return

      return null;

    }

  }







如有疑问请留言或者到本站社区交流讨论，感谢阅读，希望能帮助到大家，谢谢大家都对本站的支持！