tomcat共享多个web应用会话的实现方法

Shun

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！