【0】README

1）本文部分文字描述转自：“深入剖析tomcat”，旨在学习“tomcat(19)Manager应用程序的servlet类” 的相关知识；

2）Manager应用程序用来管理已经部署的web 应用程序；在tomcat7中，manager应用程序位于 %CATALINA_HOME%webapps 目录中；

【1】使用Manager应用程序

1）Manager应用程序中的主servlet类是 ManagerServlet类。在tomcat4中， 该类位于 org.apache.catalina.servlets包下； 而在tomcat5中，该类位于 org.apache.catalina.manager下，是作为 WEB-INF/lib 目录下的一个JAR 文件部署的；

<?xml version="1.0" encoding="ISO-8859-1"?>
<!-- tomcat7 下面的 web.xml -->Licensed to the Apache Software Foundation (ASF) under one or morecontributor license agreements.  See the NOTICE file distributed withthis work for additional information regarding copyright ownership.The ASF licenses this file to You under the Apache License, Version 2.0(the "License"); you may not use this file except in compliance withthe License.  You may obtain a copy of the License athttp://www.apache.org/licenses/LICENSE-2.0Unless required by applicable law or agreed to in writing, softwaredistributed under the License is distributed on an "AS IS" BASIS,WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.See the License for the specific language governing permissions andlimitations under the License.
--><web-app xmlns="http://java.sun.com/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/javaeehttp://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"version="3.0"metadata-complete="true"><display-name>Tomcat Manager Application</display-name><description>A scriptable management web application for the Tomcat Web Server;Manager lets you view, load/unload/etc particular web applications.</description><servlet><servlet-name>Manager</servlet-name><servlet-class>org.apache.catalina.manager.ManagerServlet</servlet-class><init-param><param-name>debug</param-name><param-value>2</param-value></init-param></servlet><servlet><servlet-name>HTMLManager</servlet-name><servlet-class>org.apache.catalina.manager.HTMLManagerServlet</servlet-class><init-param><param-name>debug</param-name><param-value>2</param-value></init-param><!-- Uncomment this to show proxy sessions from the Backup manager or aStoreManager in the sessions list for an application<init-param><param-name>showProxySessions</param-name><param-value>true</param-value></init-param>--><multipart-config><!-- 50MB max --><max-file-size>52428800</max-file-size><max-request-size>52428800</max-request-size><file-size-threshold>0</file-size-threshold></multipart-config></servlet><servlet><servlet-name>Status</servlet-name><servlet-class>org.apache.catalina.manager.StatusManagerServlet</servlet-class><init-param><param-name>debug</param-name><param-value>0</param-value></init-param></servlet><servlet><servlet-name>JMXProxy</servlet-name><servlet-class>org.apache.catalina.manager.JMXProxyServlet</servlet-class></servlet><!-- Define the Manager Servlet Mapping --><servlet-mapping><servlet-name>Manager</servlet-name><url-pattern>/text/*</url-pattern></servlet-mapping><servlet-mapping><servlet-name>Status</servlet-name><url-pattern>/status/*</url-pattern></servlet-mapping><servlet-mapping><servlet-name>JMXProxy</servlet-name><url-pattern>/jmxproxy/*</url-pattern></servlet-mapping><servlet-mapping><servlet-name>HTMLManager</servlet-name><url-pattern>/html/*</url-pattern></servlet-mapping><filter><filter-name>SetCharacterEncoding</filter-name><filter-class>org.apache.catalina.filters.SetCharacterEncodingFilter</filter-class><init-param><param-name>encoding</param-name><param-value>UTF-8</param-value></init-param></filter><filter-mapping><filter-name>SetCharacterEncoding</filter-name><url-pattern>/*</url-pattern></filter-mapping><filter><filter-name>CSRF</filter-name><filter-class>org.apache.catalina.filters.CsrfPreventionFilter</filter-class><init-param><param-name>entryPoints</param-name><param-value>/html,/html/,/html/list,/index.jsp</param-value></init-param></filter><filter-mapping><filter-name>CSRF</filter-name><servlet-name>HTMLManager</servlet-name><servlet-name>jsp</servlet-name></filter-mapping><!-- Define a Security Constraint on this Application --><!-- NOTE:  None of these roles are present in the default users file --><security-constraint><web-resource-collection><web-resource-name>HTML Manager interface (for humans)</web-resource-name><url-pattern>/html/*</url-pattern></web-resource-collection><auth-constraint><role-name>manager-gui</role-name></auth-constraint></security-constraint><security-constraint><web-resource-collection><web-resource-name>Text Manager interface (for scripts)</web-resource-name><url-pattern>/text/*</url-pattern></web-resource-collection><auth-constraint><role-name>manager-script</role-name></auth-constraint></security-constraint><security-constraint><web-resource-collection><web-resource-name>JMX Proxy interface</web-resource-name><url-pattern>/jmxproxy/*</url-pattern></web-resource-collection><auth-constraint><role-name>manager-jmx</role-name></auth-constraint></security-constraint><security-constraint><web-resource-collection><web-resource-name>Status interface</web-resource-name><url-pattern>/status/*</url-pattern></web-resource-collection><auth-constraint><role-name>manager-gui</role-name><role-name>manager-script</role-name><role-name>manager-jmx</role-name><role-name>manager-status</role-name></auth-constraint></security-constraint><!-- Define the Login Configuration for this Application --><login-config><auth-method>BASIC</auth-method><realm-name>Tomcat Manager Application</realm-name></login-config><!-- Security roles referenced by this web application --><security-role><description>The role that is required to access the HTML Manager pages</description><role-name>manager-gui</role-name></security-role><security-role><description>The role that is required to access the text Manager pages</description><role-name>manager-script</role-name></security-role><security-role><description>The role that is required to access the HTML JMX Proxy</description><role-name>manager-jmx</role-name></security-role><security-role><description>The role that is required to access to the Manager Status pages</description><role-name>manager-status</role-name></security-role><error-page><error-code>401</error-code><location>/WEB-INF/jsp/401.jsp</location></error-page><error-page><error-code>403</error-code><location>/WEB-INF/jsp/403.jsp</location></error-page><error-page><error-code>404</error-code><location>/WEB-INF/jsp/404.jsp</location></error-page></web-app>

对以上代码的分析（Analysis）：

2）在部署描述符中，还有 security-constraint 元素：（also tomcat7）

 <!-- Define a Security Constraint on this Application --><!-- NOTE:  None of these roles are present in the default users file --><security-constraint><web-resource-collection><web-resource-name>HTML Manager interface (for humans)</web-resource-name><url-pattern>/html/*</url-pattern></web-resource-collection><auth-constraint><role-name>manager-gui</role-name></auth-constraint></security-constraint><security-constraint><web-resource-collection><web-resource-name>Text Manager interface (for scripts)</web-resource-name><url-pattern>/text/*</url-pattern></web-resource-collection><auth-constraint><role-name>manager-script</role-name></auth-constraint></security-constraint><security-constraint><web-resource-collection><web-resource-name>JMX Proxy interface</web-resource-name><url-pattern>/jmxproxy/*</url-pattern></web-resource-collection><auth-constraint><role-name>manager-jmx</role-name></auth-constraint></security-constraint><security-constraint><web-resource-collection><web-resource-name>Status interface</web-resource-name><url-pattern>/status/*</url-pattern></web-resource-collection><auth-constraint><role-name>manager-gui</role-name><role-name>manager-script</role-name><role-name>manager-jmx</role-name><role-name>manager-status</role-name></auth-constraint></security-constraint>

对上述代码的分析（Analysis）：

3）在tomcat中，用户和角色列表都存储在 tomcat-users.xml 中，该文件位于 %CATALINA_HOME%/conf 目录下。因此，要访问 Manager应用程序，必须添加一个 manager角色（如manager-gui）和一个拥有该角色的用户， 例如：

<tomcat-users><role rolename="<span style="font-family: Arial, Helvetica, sans-serif;">manager-gui</span><span style="font-family: Arial, Helvetica, sans-serif;">"/></span><user username="tomcat" password="tomcat" roles="manager-gui"/>
</tomcat-users>

对以上代码的分析（Analysis）：通过这个 tomcat-users.xml 文件，就可以以tomcat为用户名，以tomcat为密码来访问 Manager 应用程序了；

【2】ContainerServlet接口（org.apache.catalina.ContainerServlet接口）

1）intro：实现该接口的 servlet类可以访问表示该 servlet实例的StandardWrapper对象，通过访问该Wrapper实例，它也就可以访问表示当前 web 应用程序的Context实例，以及该Context实例内的部署器（StandardHost类的实例）等对象；

public interface ContainerServlet {   public Wrapper getWrapper();public void setWrapper(Wrapper wrapper);
} 

2）Catalina实例会调用实现了 ContainerServlet接口的servlet类的 setWrapper方法：将该引用传递给表示该servlet类 的 StandardWrapper实例；

【3】初始化 ManagerServlet

1）intro：servlet 对象由一个 org.apache.catalina.core.StandardWrapper 实例表示，第一次调用servlet实例时，会调用 StandardWrapper.loadServlet()方法，然后调用 servlet实例的init()方法；

（下面的图片借用自tomcat(5)servlet容器 章节5.7）

【4】列出已经部署的web 应用程序 

1）通过 http://localhost:8888/manager/list 列出已经部署的web 应用程序；

2）上面的URL 会调用 ManagerServlet.list()方法， 源码如下：

 protected void list(PrintWriter writer) { // org.apache.catalina.manager.ManagerServlet.list().if (debug >= 1)log("list: Listing contexts for virtual host '" +deployer.getName() + "'");writer.println(sm.getString("managerServlet.listed",deployer.getName()));String contextPaths[] = deployer.findDeployedApps();for (int i = 0; i < contextPaths.length; i++) {Context context = deployer.findDeployedApp(contextPaths[i]);String displayPath = contextPaths[i];if( displayPath.equals("") )displayPath = "/";if (context != null ) {if (context.getAvailable()) {writer.println(sm.getString("managerServlet.listitem",displayPath,"running","" + context.getManager().findSessions().length,context.getDocBase()));} else {writer.println(sm.getString("managerServlet.listitem",displayPath,"stopped","0",context.getDocBase()));}}}}

对以上代码的分析（Analysis）：

【5】启动web 应用程序

1）使用如下URL 来启动某个web 应用程序： http://localhost:8888/manager/start?path=ContextPath ， 而ContextPath是想要启动web 应用程序的路径；

2）在接收到该URL后，会调用 ManagerServlet.start() 方法；

protected void start(PrintWriter writer, String path) { //org.apache.catalina.manager.ManagerServlet.start().if (debug >= 1)log("start: Starting web application at '" + path + "'");if ((path == null) || (!path.startsWith("/") && path.equals(""))) {writer.println(sm.getString("managerServlet.invalidPath", path));return;}String displayPath = path;if( path.equals("/") )path = "";try {Context context = deployer.findDeployedApp(path); // highlight line.if (context == null) {writer.println(sm.getString("managerServlet.noContext", displayPath));return;}deployer.start(path);// highlight line.if (context.getAvailable())writer.println(sm.getString("managerServlet.started", displayPath));elsewriter.println(sm.getString("managerServlet.startFailed", displayPath));} //......}
public void start(String contextPath) throws IOException { //org.apahce.catalina.core.StandardHostDeployer.start().// Validate the format and state of our argumentsif (contextPath == null)throw new IllegalArgumentException(sm.getString("standardHost.pathRequired"));if (!contextPath.equals("") && !contextPath.startsWith("/"))throw new IllegalArgumentException(sm.getString("standardHost.pathFormat", contextPath));Context context = findDeployedApp(contextPath);if (context == null)throw new IllegalArgumentException(sm.getString("standardHost.pathMissing", contextPath));host.log("standardHost.start " + contextPath);try {((Lifecycle) context).start(); // highlight line.启动Context容器.} //......}

对以上代码的分析（Analysis）：在执行一些检查工作后，start()方法会在 try代码块中调用部署器的 findDeployedApp()方法，该方法返回参数path 指向的Context对象。如果context不是null，start()方法调用部署器的start()方法来启动该 web 应用程序；

【6】关闭web 应用程序 

1）intro：使用如下URL 关闭某个web 应用程序：  http://localhost:8888/manager/stop?path=ContextPath；

2）在接收到该URL后，会调用 ManagerServlet.stop() 方法；

protected void stop(PrintWriter writer, String path) { //org.apache.catalina.manager.ManagerServlet.stop().if (debug >= 1)log("stop: Stopping web application at '" + path + "'");if ((path == null) || (!path.startsWith("/") && path.equals(""))) {writer.println(sm.getString("managerServlet.invalidPath", path));return;}String displayPath = path;if( path.equals("/") )path = "";try {Context context = deployer.findDeployedApp(path); //highlight line.if (context == null) {writer.println(sm.getString("managerServlet.noContext", displayPath));return;}// It isn't possible for the manager to stop itselfif (context.getPath().equals(this.context.getPath())) {writer.println(sm.getString("managerServlet.noSelf"));return;}deployer.stop(path); // highlight line.writer.println(sm.getString("managerServlet.stopped", displayPath));} //.....}
public void stop(String contextPath) throws IOException { //org.apahce.catalina.core.StandardHostDeployer.start().// Validate the format and state of our argumentsif (contextPath == null)throw new IllegalArgumentException(sm.getString("standardHost.pathRequired"));if (!contextPath.equals("") && !contextPath.startsWith("/"))throw new IllegalArgumentException(sm.getString("standardHost.pathFormat", contextPath));Context context = findDeployedApp(contextPath);if (context == null)throw new IllegalArgumentException(sm.getString("standardHost.pathMissing", contextPath));host.log("standardHost.stop " + contextPath);try {((Lifecycle) context).stop(); //highlight line. 停止该容器.} catch (LifecycleException e) {host.log("standardHost.stop " + contextPath + ": ", e);throw new IllegalStateException("standardHost.stop " + contextPath + ": " + e);}}
public synchronized void stop() throws LifecycleException { // org.apache.catalina.core.StandardContext.stop().// Validate and update our current component stateif (!started)throw new LifecycleException(sm.getString("containerBase.notStarted", logName()));if (debug >= 1)log("Stopping");// Notify our interested LifecycleListenerslifecycle.fireLifecycleEvent(BEFORE_STOP_EVENT, null);// Mark this application as unavailable while we shut downsetAvailable(false);// Binding threadClassLoader oldCCL = bindThread();// Stop our filtersfilterStop();// Stop our application listenerslistenerStop();// Finalize our character set mappersetCharsetMapper(null);if ((manager != null) && (manager instanceof Lifecycle)) {((Lifecycle) manager).stop();}// Normal container shutdown processingif (debug >= 1)log("Processing standard container shutdown");// Notify our interested LifecycleListenerslifecycle.fireLifecycleEvent(STOP_EVENT, null);started = false;try {// Stop the Valves in our pipeline (including the basic), if anyif (pipeline instanceof Lifecycle) {((Lifecycle) pipeline).stop();}// Stop our child containers, if anyContainer children[] = findChildren();for (int i = 0; i < children.length; i++) {if (children[i] instanceof Lifecycle)((Lifecycle) children[i]).stop();}// Stop our Mappers, if anyMapper mappers[] = findMappers();for (int i = 0; i < mappers.length; i++) {if (mappers[(mappers.length-1)-i] instanceof Lifecycle)((Lifecycle) mappers[(mappers.length-1)-i]).stop();}// Stop resourcesresourcesStop();if ((realm != null) && (realm instanceof Lifecycle)) {((Lifecycle) realm).stop();}if ((cluster != null) && (cluster instanceof Lifecycle)) {((Lifecycle) cluster).stop();}if ((logger != null) && (logger instanceof Lifecycle)) {((Lifecycle) logger).stop();}if ((loader != null) && (loader instanceof Lifecycle)) {((Lifecycle) loader).stop();}} finally {// Unbinding threadunbindThread(oldCCL);}// Reset application contextcontext = null;// Notify our interested LifecycleListenerslifecycle.fireLifecycleEvent(AFTER_STOP_EVENT, null); if (debug >= 1)log("Stopping complete");}

Conclusion）