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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