Tomcat8.x Servlet应用 Session的机制（初始化、读取、序列化）
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// 《Tomcat8.x Servlet应用 Session的机制 》// ----------------------------------// 创建Session管理器，Session的初始化 -------------1// ----------------------------------class org.apache.catalina.core.StandardContext{protected synchronized void startInternal() throws LifecycleException {// Acquire clustered manager Manager contextManager = null; Manager manager = getManager(); if (manager == null) { if ( (getCluster() != null) && distributable) { // 如果有配置集群/并且启动了分布式 try { contextManager = getCluster().createManager(getName()); } catch (Exception ex) { log.error("standardContext.clusterFail", ex); ok = false; } } else { contextManager = new StandardManager(); // 上下文管理器，Session管理器 } } // Configure default manager if none was specified if (contextManager != null) { setManager(contextManager); // 设置上下文管理器，Session管理器 } // Start manager Manager manager = getManager(); if (manager instanceof Lifecycle) { // org.apache.catalina.session.StandardManager ((Lifecycle) manager).start(); // 启动上下文管理器，即启动Session管理器，加载服务器上的Session文件 }}}// Session管理器class org.apache.catalina.session.StandardManager{protected synchronized void startInternal() throws LifecycleException { super.startInternal(); // Load unloaded sessions, if any load(); // 加载服务器上的Session文件 setState(LifecycleState.STARTING); }// 加载服务器上的Session文件public void load() throws ClassNotFoundException, IOException { doLoad(); // 加载服务器上的Session文件 }// 加载服务器上的Session文件protected void doLoad() throws ClassNotFoundException, IOException { // Initialize our internal data structures sessions.clear(); // Open an input stream to the specified pathname, if any File file = file();//!!! 在临时目录中读取Session信息 if (file == null) { return; } Loader loader = null; ClassLoader classLoader = null; Log logger = null; try (FileInputStream fis = new FileInputStream(file.getAbsolutePath()); BufferedInputStream bis = new BufferedInputStream(fis)) { // org.apache.catalina.core.StandardContext Context c = getContext(); loader = c.getLoader(); logger = c.getLogger(); if (loader != null) { classLoader = loader.getClassLoader(); } if (classLoader == null) { classLoader = getClass().getClassLoader(); } // Load the previously unloaded active sessions synchronized (sessions) { // 解析Session文件内容 try (ObjectInputStream ois = new CustomObjectInputStream(bis, classLoader, logger, getSessionAttributeValueClassNamePattern(), getWarnOnSessionAttributeFilterFailure())) { // 读取d:/a/b/tomcat8.x/work/Catalina/localhost/test/SESSIONS.ser Integer count = (Integer) ois.readObject(); // 读取Session对象 int n = count.intValue(); for (int i = 0; i < n; i++) { // org.apache.catalina.session.StandardSession StandardSession session = getNewSession(); // 创建StandardSession session.readObjectData(ois); // 解析Session文件 session.setManager(this); sessions.put(session.getIdInternal(), session); session.activate(); if (!session.isValidInternal()) { // 检查是否失效 // If session is already invalid, // expire session to prevent memory leak. session.setValid(true); session.expire(); } sessionCounter++; } } finally { // Delete the persistent storage file if (file.exists()) { file.delete(); } } } } }// 查找Session文件protected File file() { if (pathname == null || pathname.length() == 0) { return null; } File file = new File(pathname);// SESSIONS.ser if (!file.isAbsolute()) { // context === org.apache.catalina.core.StandardContext Context context = getContext(); ServletContext servletContext = context.getServletContext(); File tempdir = (File) servletContext.getAttribute(ServletContext.TEMPDIR); if (tempdir != null) { file = new File(tempdir, pathname); // 从临时目录中加载Session文件 } } return file; }}// ----------------------------------// Session 的调用 -------------2// ----------------------------------HttpSession httpSession = req.getSession();httpSession.setAttribute("userInfo", "userInfo_Value");httpSession.getAttribute("userInfo");class org.apache.catalina.connector.RequestFacade{public HttpSession getSession() { return getSession(true); }public HttpSession getSession(boolean create) { return request.getSession(create); }}class org.apache.catalina.connector.Request{public HttpSession getSession(boolean create) { Session session = doGetSession(create);//!!! if (session == null) { return null; } return session.getSession(); }protected Session doGetSession(boolean create) { // There cannot be a session if no context has been assigned yet Context context = getContext(); // org.apache.catalina.core.StandardContext if (context == null) { return (null); } // Return the current session if it exists and is valid if ((session != null) && !session.isValid()) { // 如果Session已经过期,从session管理中删除本对象,就返回空 session = null; } if (session != null) { return (session); } // Return the requested session if it exists and is valid // org.apache.catalina.session.StandardManager Manager manager = context.getManager(); if (manager == null) { return (null); // Sessions are not supported } if (requestedSessionId != null) { try { // manager === org.apache.catalina.session.StandardManager //查找SessionID是否已经存在 session = manager.findSession(requestedSessionId); } catch (IOException e) { session = null; } if ((session != null) && !session.isValid()) { // 如果Session已经过期,从session管理中删除本对象,就返回空 session = null; } if (session != null) { session.access(); return (session); } } // Create a new session if requested and the response is not committed if (!create) { return (null); } if (response != null && context.getServletContext() .getEffectiveSessionTrackingModes() .contains(SessionTrackingMode.COOKIE) && response.getResponse().isCommitted()) { // 如果在cookie发送之前已经发送了其他响应内容了，就报错 throw new IllegalStateException( sm.getString("coyoteRequest.sessionCreateCommitted")); } String sessionId = getRequestedSessionId(); if (requestedSessionSSL) { // If the session ID has been obtained from the SSL handshake then // use it. } else if (("/".equals(context.getSessionCookiePath()) && isRequestedSessionIdFromCookie())) { if (context.getValidateClientProvidedNewSessionId()) { boolean found = false; for (Container container : getHost().findChildren()) { Manager m = ((Context) container).getManager(); if (m != null) { try { if (m.findSession(sessionId) != null) { found = true; break; } } catch (IOException e) { // Ignore. Problems with this manager will be // handled elsewhere. } } } if (!found) { sessionId = null; } } } else { sessionId = null; } // manager == org.apache.catalina.session.StandardManager session = manager.createSession(sessionId);//!!!! 创建Session对象 // Creating a new session cookie based on that session if (session != null && context.getServletContext() .getEffectiveSessionTrackingModes() .contains(SessionTrackingMode.COOKIE)) { // 创建Session的Cookie Cookie cookie = ApplicationSessionCookieConfig.createSessionCookie( context, session.getIdInternal(), isSecure()); // 添加响应Cookie response.addSessionCookieInternal(cookie); } if (session == null) { return null; } session.access();//!!! // 访问次数+1 return session; }}// ----------------------------------// Session 的调用 -------------的保存（序列化）// ----------------------------------class org.apache.catalina.core.StandardContext{protected synchronized void stopInternal() throws LifecycleException {// 保存Session信息// manager == org.apache.catalina.session.StandardManager Manager manager = getManager(); if (manager instanceof Lifecycle && ((Lifecycle) manager).getState().isAvailable()) { ((Lifecycle) manager).stop(); }}}class org.apache.catalina.session.StandardManager{protected synchronized void stopInternal() throws LifecycleException { setState(LifecycleState.STOPPING); // Write out sessions try { unload(); // 保存Session数据到文件中 } catch (Throwable t) { } // Expire all active sessions 让活动中的Session全部失效 Session sessions[] = findSessions(); for (int i = 0; i < sessions.length; i++) { Session session = sessions[i]; if (session.isValid()) { session.expire(); // } } // Require a new random number generator if we are restarted super.stopInternal(); }// 保存Session数据到文件中public void unload() throws IOException { doUnload(); }protected void doUnload() throws IOException { // Open an output stream to the specified pathname, if any File file = file(); if (file == null) { return; } // Keep a note of sessions that are expired ArrayList<StandardSession> list = new ArrayList<>(); try (FileOutputStream fos = new FileOutputStream(file.getAbsolutePath()); BufferedOutputStream bos = new BufferedOutputStream(fos); ObjectOutputStream oos = new ObjectOutputStream(bos)) { // 写入d:/a/b/tomcat8.x/work/Catalina/localhost/test/SESSIONS.ser synchronized (sessions) { // Write the number of active sessions, followed by the details oos.writeObject(Integer.valueOf(sessions.size())); Iterator<Session> elements = sessions.values().iterator(); while (elements.hasNext()) { StandardSession session = (StandardSession) elements.next(); list.add(session); session.passivate(); session.writeObjectData(oos); // 写入Session的数据 } } } // Expire all the sessions we just wrote Iterator<StandardSession> expires = list.iterator(); while (expires.hasNext()) { // org.apache.catalina.session.StandardSession StandardSession session = expires.next(); try { session.expire(false); } catch (Throwable t) { ExceptionUtils.handleThrowable(t); } finally { session.recycle(); } } }protected File file() { if (pathname == null || pathname.length() == 0) { return null; } File file = new File(pathname);// SESSIONS.ser if (!file.isAbsolute()) { // context === org.apache.catalina.core.StandardContext Context context = getContext(); ServletContext servletContext = context.getServletContext(); File tempdir = (File) servletContext.getAttribute(ServletContext.TEMPDIR); if (tempdir != null) { file = new File(tempdir, pathname); // 从临时目录中加载Session文件 } } return file; }} 0 0
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