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;
        }
      }
    
    

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