Tomcat源码分析(三)-Container和Lifecycle

谁践踏了优雅 2022-05-14 00:53 130阅读 0赞

**一、Tomcat生命周期的管理**

Tomcat通过package org.apache.catalina.Lifecycle;接口管理Tomcat的生命周期。

package org.apache.catalina;
    
    public interface Lifecycle {
    //定义的String常量，用于LifecycleEvent事件的type属性中，作用是区分组件发出的LifecycleEvent事件时的状态(如初始化前，启动前，启动中等)
    
        public static final String BEFORE_INIT_EVENT = "before_init";
    
        public static final String AFTER_INIT_EVENT = "after_init";
    
        public static final String START_EVENT = "start";
    
        public static final String BEFORE_START_EVENT = "before_start";
    
        public static final String AFTER_START_EVENT = "after_start";
    
        public static final String STOP_EVENT = "stop";
    
        public static final String BEFORE_STOP_EVENT = "before_stop";
    
        public static final String AFTER_STOP_EVENT = "after_stop";
    
        public static final String AFTER_DESTROY_EVENT = "after_destroy";
    
        public static final String BEFORE_DESTROY_EVENT = "before_destroy";
    
        public static final String PERIODIC_EVENT = "periodic";
    
        public static final String CONFIGURE_START_EVENT = "configure_start";
    
        public static final String CONFIGURE_STOP_EVENT = "configure_stop";
    
        public void addLifecycleListener(LifecycleListener listener); //添加LifecycleListener
                                                                      //监听器
    
        public LifecycleListener[] findLifecycleListeners(); 
    
        public void init() throws LifecycleException;
    
      
        public void start() throws LifecycleException;
    
        public void stop() throws LifecycleException;
    
        public void destroy() throws LifecycleException;
    
        public LifecycleState getState();
    
        public String getStateName();
    
        public interface SingleUse {
        }
    }

所有生命周期的组件都要实现Lifecycle接口。

![70][]

LifecycleBase是Lifecycle的默认实现。Server,Service等生命周期组件直接或间接继承了LifecycleBase；

LifecycleBase里面定义了一个 LifecycleSupport类来管理监听器。

/**
         * Used to handle firing lifecycle events.
         * TODO: Consider merging LifecycleSupport into this class.
         */
        private final LifecycleSupport lifecycle = new LifecycleSupport(this);

LifecycleSupport代码如下：

/**
 * Support class to assist in firing LifecycleEvent notifications to
 * registered LifecycleListeners.
 *
 * @author Craig R. McClanahan
 */
 public final class LifecycleSupport {
 
 // ----------------------------------------------------------- Constructors
 
 /**
 * Construct a new LifecycleSupport object associated with the specified
 * Lifecycle component.
 *
 * @param lifecycle The Lifecycle component that will be the source
 * of events that we fire
 */
 public LifecycleSupport(Lifecycle lifecycle) {
 super();
 this.lifecycle = lifecycle;
 }
 
 
 // ----------------------------------------------------- Instance Variables
 
 /**
 * The source component for lifecycle events that we will fire.
 */
 private final Lifecycle lifecycle;
 
 
 /**
 * The list of registered LifecycleListeners for event notifications.
 */
 private final List<LifecycleListener> listeners = new CopyOnWriteArrayList<>();
 
 
 // --------------------------------------------------------- Public Methods
 
 /**
 * Add a lifecycle event listener to this component.
 *
 * @param listener The listener to add
 */
 public void addLifecycleListener(LifecycleListener listener) {
 listeners.add(listener);
 }
 
 
 /**
 * Get the lifecycle listeners associated with this lifecycle. If this
 * Lifecycle has no listeners registered, a zero-length array is returned.
 */
 public LifecycleListener[] findLifecycleListeners() {
 return listeners.toArray(new LifecycleListener[0]);
 }
 
 
 /**
 * Notify all lifecycle event listeners that a particular event has
 * occurred for this Container. The default implementation performs
 * this notification synchronously using the calling thread.
 *
 * @param type Event type
 * @param data Event data
 */
 public void fireLifecycleEvent(String type, Object data) {
 LifecycleEvent event = new LifecycleEvent(lifecycle, type, data);
 for (LifecycleListener listener : listeners) {
 listener.lifecycleEvent(event);
 }
 }
 
 
 /**
 * Remove a lifecycle event listener from this component.
 *
 * @param listener The listener to remove
 */
 public void removeLifecycleListener(LifecycleListener listener) {
 listeners.remove(listener);
 }
 }

而在LifecycleSupport类里面定义了一个LifecycleListener集合类型来保存LifecycleListener监听器。

代码如下:

LifecycleListener类代码如下：

/**
     * Interface defining a listener for significant events (including "component
     * start" and "component stop" generated by a component that implements the
     * Lifecycle interface. The listener will be fired after the associated state
     * change has taken place.
     *
     * @author Craig R. McClanahan
     */
    public interface LifecycleListener {
    
    
        /**
         * Acknowledge the occurrence of the specified event.
         *
         * @param event LifecycleEvent that has occurred
         */
        public void lifecycleEvent(LifecycleEvent event);
    
    
    }

**   二、 LifecycleBase类的生命周期方法分析：**

**        **   四个生命周期方法分别是 init(),start(),stop(),destroy()方法。都会线判断状态和当前方法是否匹配。

如在init方法之前调用了start方法。这时会先执行init方法。

LifecycleBase的状态是通过LifecycleBase类型的state属性来保存的，最开始初始化值为LifecycleState.NEW.  
**           initInternal()和startInternal()模板方法会调用具体的子类具体来启动。**

LifecycleBase类的init方法代码如下:

@Override
        public final synchronized void init() throws LifecycleException {
            if (!state.equals(LifecycleState.NEW)) {//如果状态不是NEW,就
                invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
            }
    
            try { //初始化前将状态设置为LifecycleState.INITIALIZING
                setStateInternal(LifecycleState.INITIALIZING, null, false);
                initInternal(); //具体执行初始化
                setStateInternal(LifecycleState.INITIALIZED, null, false);
            } catch (Throwable t) {
                ExceptionUtils.handleThrowable(t);
                setStateInternal(LifecycleState.FAILED, null, false);
                throw new LifecycleException(
                        sm.getString("lifecycleBase.initFail",toString()), t);
            }
        }
    
    
        protected abstract void initInternal() throws LifecycleException;

//invalidTransition 抛出LifecycleException异常  
       //处理不符合要求的状态
       private void invalidTransition(String type) throws LifecycleException {
            String msg = sm.getString("lifecycleBase.invalidTransition", type,
                    toString(), state);
            throw new LifecycleException(msg);
        }

private synchronized void setStateInternal(LifecycleState state,
                Object data, boolean check) throws LifecycleException {
    
            if (log.isDebugEnabled()) {
                log.debug(sm.getString("lifecycleBase.setState", this, state));
            }
    
            if (check) {  //check 该段主要是校验state状态，state为null抛出异常，
                          //state不是FAILED 并且state不是STARTING或者this.state不是STARTING_PREP 或state不是STARTING，this.state也不是STARTING_PREP (省略。。)才会抛出异常，无法识别得到state.
                          //state可以是FAILED 
                          //state可以是STARTING,this.state可以是STARTING_PREP 
                          //state可以是STOPPING,this.state可以是STOPPING_PREP 
                          //state可以是STOPPING,this.state可以是FAILED 都不会进入异常
                // Must have been triggered by one of the abstract methods (assume
                // code in this class is correct)
                // null is never a valid state
                if (state == null) {
                    invalidTransition("null");
                    // Unreachable code - here to stop eclipse complaining about
                    // a possible NPE further down the method
                    return;
                }
    
                // Any method can transition to failed
                // startInternal() permits STARTING_PREP to STARTING
                // stopInternal() permits STOPPING_PREP to STOPPING and FAILED to
                // STOPPING
                if (!(
                        state == LifecycleState.FAILED ||
                        (this.state == LifecycleState.STARTING_PREP &&
                                state == LifecycleState.STARTING) ||
                        (this.state == LifecycleState.STOPPING_PREP &&
                                state == LifecycleState.STOPPING) ||
                        (this.state == LifecycleState.FAILED &&
                                state == LifecycleState.STOPPING)
                        )) {
                    // No other transition permitted
                    invalidTransition(state.name());
                }
            }
    
            this.state = state;
            String lifecycleEvent = state.getLifecycleEvent();
            if (lifecycleEvent != null) {  
                fireLifecycleEvent(lifecycleEvent, data); //处理事件
            }
        }

setStateInternal()方法中通过check参数来判断是否需要检查传入的状态state.如果需要检查则会检查传入的状态是否为空和是否符合正确的状态，最后设置state.

LifecycleBase类的start方法代码如下:

/**
         * {@inheritDoc}
         */
        @Override
        public final synchronized void start() throws LifecycleException {
            //检查状态是否已经启动,如果已经启动打印log
            if (LifecycleState.STARTING_PREP.equals(state) || LifecycleState.STARTING.equals(state) ||
                    LifecycleState.STARTED.equals(state)) {
    
                if (log.isDebugEnabled()) {
                    Exception e = new LifecycleException();
                    log.debug(sm.getString("lifecycleBase.alreadyStarted", toString()), e);
                } else if (log.isInfoEnabled()) {
                    log.info(sm.getString("lifecycleBase.alreadyStarted", toString()));
                }
    
                return;
            }
    
            if (state.equals(LifecycleState.NEW)) {
                init();
            } else if (state.equals(LifecycleState.FAILED)) { //状态失败停止
                stop();
            } else if (!state.equals(LifecycleState.INITIALIZED) &&
                    !state.equals(LifecycleState.STOPPED)) {  //如果状态无法识别，抛出异常
                invalidTransition(Lifecycle.BEFORE_START_EVENT);
            }
    
            try {
                setStateInternal(LifecycleState.STARTING_PREP, null, false);
                startInternal();
                if (state.equals(LifecycleState.FAILED)) {
                    // This is a 'controlled' failure. The component put itself into the
                    // FAILED state so call stop() to complete the clean-up.
                    stop();
                } else if (!state.equals(LifecycleState.STARTING)) {//如果启动后状态不是
                                                                   //STARTING则抛出异常
                    // Shouldn't be necessary but acts as a check that sub-classes are
                    // doing what they are supposed to.
                    invalidTransition(Lifecycle.AFTER_START_EVENT);
                } else {                                          
                                                              //启动成功后将状态设为STARTED
                    setStateInternal(LifecycleState.STARTED, null, false);
                }
            } catch (Throwable t) {
                // This is an 'uncontrolled' failure so put the component into the
                // FAILED state and throw an exception.
                ExceptionUtils.handleThrowable(t);
                setStateInternal(LifecycleState.FAILED, null, false);
                throw new LifecycleException(sm.getString("lifecycleBase.startFail", toString()), t);
            }
        }

**三、Container源码分析**

**    Container的作用是具体负责处理Servlet,处理Http请求。**

![70 1][]

![70 2][]

![70 3][]

public interface Container extends Lifecycle \{

Container 四个子容器 Engine,Host,Context,Wrapper逐层包含的关系。

Engine 引擎，用来管理多个站点。

Host 站点(虚拟主机)，整个webapps是一个站点，如：www.test.com域名对应webapps目录所代表的站点，其中ROOT目录 是主应用，直接使用域名就可以访问主应用。而webapps/test是test子应用，访问www.test.com/test

Context 应用程序，默认配置下webapps下的每个目录都市一个应用。其中ROOT目录存放着主应用，其他目录是子应用。

Wrapper 每个Wrapper封装一个Servlet.

**配置：**

Server.xml文件里面放了Tomcat大部分功能的配置。

Server.xml文件默认配置如下:

<?xml version="1.0" encoding="UTF-8"?>
 <Server port="8005" shutdown="SHUTDOWN">
 <Listener className="org.apache.catalina.startup.VersionLoggerListener"/>
 <Listener SSLEngine="on" className="org.apache.catalina.core.AprLifecycleListener"/>
 <Listener className="org.apache.catalina.core.JasperListener"/>
 
 <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener"/>
 <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener"/>
 <Listener className="org.apache.catalina.core.ThreadLocalLeakPreventionListener"/>
 <GlobalNamingResources>
 <Resource auth="Container" description="User database that can be updated and saved" factory="org.apache.catalina.users.MemoryUserDatabaseFactory" name="UserDatabase" pathname="conf/tomcat-users.xml" type="org.apache.catalina.UserDatabase"/>
 </GlobalNamingResources>
 
 <Service name="Catalina">
 <Connector connectionTimeout="20000" port="8080" protocol="HTTP/1.1" redirectPort="8443"/>
 <Connector port="8009" protocol="AJP/1.3" redirectPort="8443"/>
 <Engine defaultHost="localhost" name="Catalina">
 <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/>
 </Realm>
 
 <Host appBase="webapps" autoDeploy="true" name="localhost" unpackWARs="true">
 <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" pattern="%h %l %u %t "%r" %s %b" prefix="localhost_access_log." suffix=".txt"/>
 
 <Context docBase="D:\apache-tomcat-7.0.69\wtpwebapps\tp-user" path="/tp-user" reloadable="true" source="org.eclipse.jst.jee.server:tp-user"/>
 </Host>
 </Engine>
 </Service>
 </Server>

以上代码定义一个Server,端口是8005，监听命令是"SHUTDOWN",

Server下定义了listener，如：org.apache.catalina.startup.VersionLoggerListener ，

Server下定义了一个 GlobalNamingResources 配置了服务器的全局JNDI资源,配置Realm,需要配置GlobalNamingResources 。

1、可以在GlobalNamingResources中嵌入 <Resource>元素，定义资源参数 。

GlobalNamingResources官网介绍：[http://tomcat.apache.org/tomcat-7.0-doc/config/globalresources.html][http_tomcat.apache.org_tomcat-7.0-doc_config_globalresources.html]

description-->资源描述，

pathname-->加载资源的路径，

type->获取该资源的时候返回的类型，

auth -->用Application登录到资源管理器，或者用Container代表应用程序登录到资源管理器。 此属性的值必须是Application或Container。 如果Web应用程序将在Web应用程序部署描述符中使用<resource-ref>元素，则此属性是必需的，但如果应用程序使用<resource-env-ref>，则该属性是可选的。

2、 可以在GlobalNamingResources中嵌套<Environment>元素，配置命名的值，这些值作为环境条目资源(Environment Entry Resource），对整个web应用可见 如在GlobalNamingResources下添加：

value:通过JNDI context请求时，返回给应用的参数值。这个值必须转换成type属性定义的Java类型.

override: 如果/WEB-INF/web.xml中具有相同名称的<env-entry>覆盖这里指定的值，设为false。缺省值为true.

name :Environment的名称

等价于在/WEB-INF/web.xml中的配置：

<env-entry>
 
 <env-entry-name>maxExemptions</param-name>
 
 <env-entry-value>10</env-entry-value>
 
 <env-entry-type>java.lang.Integer</env-entry-type>
 
 </env-entry>

Server下定义了一个名为"Catalina"的Service ,Service里面定义了两个Connector ,一个是HTTP协议,一个是AJP协议(主要用于集成,与apache集成等)，Service下面定义了名为 "Catalina"的Engine,默认站点是localhost。

Engine下定义了一个Host ,Host的appBase的每个文件夹里都代表一个应用，上面定义的站点就是默认是webapps目录，unpackWARs表示十分自动解压war文件,autoDeploy表示是否自动部署，为true，webapps下加入的应用会自动部署并启动。

Engin下定义了一个Realm,用于身份验证等安全机制.如果不指定，则使用Engine的Realm。

<Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> 
      </Realm> 对一个UserDatabase Realm的配置，它让默认的web应用程序（manager）加载tomcat-user.xml来进行用户验证.

Realm可以从这些数据源获取用户验证数据：

* memory：使用在内存中存放的一个表格进行验证。这个表格时在tomcat启动时从一个xml文件加载到内存中的，在这个表格中的信息格式一般为：用户名/密码/角色。这种方式一般只用于测试和开发阶段. 配置方式如下<Realm className="org.apache.catalina.realm.MemoryRealm"/> 默认是读取 tomcat-users.xml
 * UserDatabase：实现了一个可以修改的、持久的memory Realm，可以向后兼容memory Realm。
 * JDBC：使用一个关系数据库存放用户验证数据
 * DataSource：类似于JDBC Realm，使用JNDI的方式来从关系数据库中拿用户验证数据，内容最终还是在一个关系数据库里。
 * JNDI：使用JNDI来获取Realm数据，这些数据一般存放在LDAP目录下。
 * JAAS:  使用JAAS来获取用户验证信息

具体的数据源配置可参考博客:[https://blog.csdn.net/conquer0715/article/details/78206874?locationNum=6&fps=1][https_blog.csdn.net_conquer0715_article_details_78206874_locationNum_6_fps_1]

Host下有一个Alias标签，<Host name="www.test.com"><Alias> test.com</Alias></Host> 表示alias别名，www.test.com和test.com访问同一个站点。

<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" pattern="%h %l %u %t "%r" %s %b" prefix="localhost\_access\_log." suffix=".txt"/>访问日志的配置，directory 指的是日志文件放置的目录，在tomcat下面有个logs文件夹，prefix日志文件的名称前缀，suffix后缀，AccessLogValve访问日志类，pattern的匹配如下：

<table style="width:432pt;"> 
 <tbody> 
 <tr> 
 <td style="border-color:#ece9d8;"> %a&nbsp;&nbsp;&nbsp;&nbsp; &nbsp; </td> 
 <td style="border-color:#ece9d8;"> 这是记录访问者的IP，在日志里是127.0.0.1 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %A </td> 
 <td style="border-color:#ece9d8;"> 这是记录本地服务器的IP，在日志里是192.168.254.108 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %b </td> 
 <td style="border-color:#ece9d8;"> 这是发送信息的字节数，不涵括http头，如果字节数为0的话，显示为- </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %B </td> 
 <td style="border-color:#ece9d8;"> 看tomcat的解释，没看出来与b%的区别，但我这里显示为-1，没想明白，望知道者告知，我把官方解释贴出来吧&nbsp;Bytes sent, excluding HTTP headers </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %h </td> 
 <td style="border-color:#ece9d8;"> 这个就是服务器名称了，如果resolveHosts为false的话，这里就是IP地址了，我的日志里是127.0.0.1 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %H </td> 
 <td style="border-color:#ece9d8;"> 访问者使用的协议，这里是HTTP/1.1 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %l </td> 
 <td style="border-color:#ece9d8;"> 这个也不太清楚，官方也说这个always return '-'&nbsp;官方解释：Remote logical username from identd (可能这样翻译：记录浏览者进行身份验证时提供的名字)(always returns '-') </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %m </td> 
 <td style="border-color:#ece9d8;"> 访问的方式，是GET还是POST，我这是GET </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %p </td> 
 <td style="border-color:#ece9d8;"> 本地接收访问的端口，呵呵，我这里是80啦 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %q </td> 
 <td style="border-color:#ece9d8;"> 比如你访问的是aaa.jsp?bbb=ccc，那么这里就显示?bbb=ccc，明白了吧，这个q是querystring的意思 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %r </td> 
 <td style="border-color:#ece9d8;"> 官方解释：First line of the request (method and request URI)，不是很明白 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %s </td> 
 <td style="border-color:#ece9d8;"> 这个是http的状态，我这里返回的是304，咱们经常看见访问某个网页报错误500什么的，那也会返回500 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %S </td> 
 <td style="border-color:#ece9d8;"> 用户的session ID,这个session ID大家可以另外查一下详细的解释，反正每次都会生成不同的session ID </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %t </td> 
 <td style="border-color:#ece9d8;"> 这就是时间啦，好像有一个Common Log Format可以改，不过我没找到 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %u </td> 
 <td style="border-color:#ece9d8;"> 得到了验证的访问者，否则就是"-" </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %U </td> 
 <td style="border-color:#ece9d8;"> 访问的URL地址，我这里是/rightmainima/leftbott4.swf </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %v </td> 
 <td style="border-color:#ece9d8;"> 服务器名称，可能就是你url里面写的那个吧，我这里是localhost </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %D </td> 
 <td style="border-color:#ece9d8;"> 官方解释：Time taken to process the request, in millis，应该是访问发生的时间，以毫秒记 </td> 
 </tr> 
 <tr> 
 <td style="border-color:#ece9d8;"> %T </td> 
 <td style="border-color:#ece9d8;"> 官方解释：Time taken to process the request, in seconds，应该是访问发生的时间，以秒记 </td> 
 </tr> 
 </tbody> 
</table>

Engin的defaultHost属性，请求的域名在所有的Host的name和Alias都找不到时才使用defaultHost(默认的Host),如果使用IP直接访问会用到defaultHost,删除Engin的defaultHost属性，无法用127.0.0.1访问本机的tomcat.

Host下的定义的Context(应用)配置--》通过文件配置，--》将WAR文件放在Host目录下 ，--》文件夹放在Host目录下。

文件配置方式:conf/server.xml 中context标签--》配置单独的应用

conf/(enginname)/(hostname)/目录下以应用命名的xml文件--》配置单独的应用

/META-INF/context.xml文件 --》配置单独的应用

conf/context.xml文件 --》Context共享（整个Tomcat共享）

conf/(enginname)/(hostname)/context.xml.default文件 --》Context共享（Host共享）

ContainerBase类：

ContainerBase类：
 
 
 /**
 * The number of threads available to process start and stop events for any
 * children associated with this container.
 */
 private int startStopThreads = 1; //启动和停止的线程数
 @Override
 protected void initInternal() throws LifecycleException {
 BlockingQueue<Runnable> startStopQueue = new LinkedBlockingQueue<>();
 //ThreadPoolExecutor继承自Executor，管理线程
 startStopExecutor = new ThreadPoolExecutor( 
 getStartStopThreadsInternal(),
 getStartStopThreadsInternal(), 10, TimeUnit.SECONDS,
 startStopQueue,
 new StartStopThreadFactory(getName() + "-startStop-"));
 startStopExecutor.allowCoreThreadTimeOut(true);
 super.initInternal();
 }
 
 /**
 * Handles the special values.
 */
 private int getStartStopThreadsInternal() {
 int result = getStartStopThreads();
 
 // Positive values are unchanged
 if (result > 0) { //线程数大于0，直接返回
 return result;
 }
 
 // Zero == Runtime.getRuntime().availableProcessors()
 // -ve == Runtime.getRuntime().availableProcessors() + value
 // These two are the same
 result = Runtime.getRuntime().availableProcessors() + result;
 if (result < 1) { //线程数小于1，也处理为1
 result = 1;
 }
 return result;
 }

ContainerBase类:
 
 /**
 * Start this component and implement the requirements
 * of {@link org.apache.catalina.util.LifecycleBase#startInternal()}.
 *
 * @exception LifecycleException if this component detects a fatal error
 * that prevents this component from being used
 */
 @Override
 protected synchronized void startInternal() throws LifecycleException {
 
 // Start our subordinate components, if any
 logger = null;
 getLogger();
 Cluster cluster = getClusterInternal();
 if ((cluster != null) && (cluster instanceof Lifecycle))
 ((Lifecycle) cluster).start(); //启动cluster
 Realm realm = getRealmInternal();
 if ((realm != null) && (realm instanceof Lifecycle))
 ((Lifecycle) realm).start(); //启动realm
 
 // Start our child containers, if any
 Container children[] = findChildren();
 List<Future<Void>> results = new ArrayList<>();
 for (int i = 0; i < children.length; i++) {
 //线程调用子容器的start方法，(children[i].start())
 results.add(startStopExecutor.submit(new StartChild(children[i])));
 }
 
 boolean fail = false;
 for (Future<Void> result : results) {
 try {
 result.get(); //获取Future返回值
 } catch (Exception e) {
 log.error(sm.getString("containerBase.threadedStartFailed"), e);
 fail = true;
 }
 
 }
 if (fail) {
 throw new LifecycleException(
 sm.getString("containerBase.threadedStartFailed"));
 }
 
 // Start the Valves in our pipeline (including the basic), if any
 if (pipeline instanceof Lifecycle)
 ((Lifecycle) pipeline).start(); //启动管道
 
 
 setState(LifecycleState.STARTING);
 
 // Start our thread
 threadStart(); //后台线程启动
 
 }

1、new StartChild(children\[i\]))分析，实现Callable接口， 调用子容器start()方法。

// ----------------------------- Inner classes used with start/stop Executor
 
 private static class StartChild implements Callable<Void> {
 
 private Container child;
 
 public StartChild(Container child) {
 this.child = child;
 }
 
 @Override
 public Void call() throws LifecycleException {
 child.start();
 return null;
 }
 }

2、 threadStart();  方法分析

ContainerBase类：
 
 /**
 * The processor delay for this component.
 */
 protected int backgroundProcessorDelay = -1; //后台线程间隔,小于0就不启动
 
 /**
 * Start the background thread that will periodically check for
 * session timeouts.
 */
 protected void threadStart() {
 
 if (thread != null)
 return;
 if (backgroundProcessorDelay <= 0)
 return;
 
 threadDone = false;
 String threadName = "ContainerBackgroundProcessor[" + toString() + "]";
 thread = new Thread(new ContainerBackgroundProcessor(), threadName);
 thread.setDaemon(true);
 thread.start();
 
 }
 
 
 /**
 * Private thread class to invoke the backgroundProcess method
 * of this container and its children after a fixed delay.
 */
 protected class ContainerBackgroundProcessor implements Runnable {
 
 @Override
 public void run() {
 Throwable t = null;
 String unexpectedDeathMessage = sm.getString(
 "containerBase.backgroundProcess.unexpectedThreadDeath",
 Thread.currentThread().getName());
 try {
 while (!threadDone) { //while循环间隔backgroundProcessorDelay * 1000L
 //调用backgroundProcess方法
 try {
 Thread.sleep(backgroundProcessorDelay * 1000L);
 } catch (InterruptedException e) {
 // Ignore
 }
 if (!threadDone) {
 processChildren(ContainerBase.this);
 }
 }
 } catch (RuntimeException|Error e) {
 t = e;
 throw e;
 } finally {
 if (!threadDone) {
 log.error(unexpectedDeathMessage, t);
 }
 }
 }
 
 protected void processChildren(Container container) {
 ClassLoader originalClassLoader = null;
 
 try {
 if (container instanceof Context) {
 Loader loader = ((Context) container).getLoader();
 // Loader will be null for FailedContext instances
 if (loader == null) {
 return;
 }
 
 // Ensure background processing for Contexts and Wrappers
 // is performed under the web app's class loader
 originalClassLoader = ((Context) container).bind(false, null);
 }
 container.backgroundProcess(); //这里调用了container的backgroundProcess
 Container[] children = container.findChildren();
 for (int i = 0; i < children.length; i++) {
 if (children[i].getBackgroundProcessorDelay() <= 0) {
 processChildren(children[i]);
 }
 }
 } catch (Throwable t) {
 ExceptionUtils.handleThrowable(t);
 log.error("Exception invoking periodic operation: ", t);
 } finally {
 if (container instanceof Context) {
 ((Context) container).unbind(false, originalClassLoader);
 }
 }
 }
 }

在processChildren()方法里面调用了 container.backgroundProcess();

具体实现类有：StandardContext,StandardWrapper类

![70 4][]

StandardContext类：    
    
        @Override
        public void backgroundProcess() {
    
            if (!getState().isAvailable())
                return;
    
            Loader loader = getLoader();   
            if (loader != null) {
                try {
                    loader.backgroundProcess();  //实现类WebappLoader类调用backgroundProcess()
                } catch (Exception e) {
                    log.warn(sm.getString(
                            "standardContext.backgroundProcess.loader", loader), e);
                }
            }
            Manager manager = getManager();
            if (manager != null) {
                try {
                    manager.backgroundProcess();  //ManageBase类实现，处理Session过期
                } catch (Exception e) {
                    log.warn(sm.getString(
                            "standardContext.backgroundProcess.manager", manager),
                            e);
                }
            }
            WebResourceRoot resources = getResources();
            if (resources != null) {
                try {
                    resources.backgroundProcess();   //cache和gc()
                } catch (Exception e) {
                    log.warn(sm.getString(
                            "standardContext.backgroundProcess.resources",
                            resources), e);
                }
            }
            InstanceManager instanceManager = getInstanceManager();
            if (instanceManager instanceof DefaultInstanceManager) {
                try {    //清除map已经过期死亡的key
                    ((DefaultInstanceManager) instanceManager).backgroundProcess();
                } catch (Exception e) {
                    log.warn(sm.getString(
                            "standardContext.backgroundProcess.instanceManager",
                            resources), e);
                }
            }
            super.backgroundProcess();
        }

**Engin:**

StandardEngin类:
      
       @Override
        protected void initInternal() throws LifecycleException {
            // Ensure that a Realm is present before any attempt is made to start
            // one. This will create the default NullRealm if necessary.
            getRealm();
            super.initInternal();
        }
    
      @Override
        protected synchronized void startInternal() throws LifecycleException {
    
            // Log our server identification information
            if(log.isInfoEnabled())
                log.info( "Starting Servlet Engine: " + ServerInfo.getServerInfo());
    
            // Standard container startup
            super.startInternal();
        }

**Host:**

org.apache.catalina.core.StandardHost类:
        private String errorReportValveClass =
            "org.apache.catalina.valves.ErrorReportValve";
       @Override
        protected synchronized void startInternal() throws LifecycleException {
    
            // Set error report valve
            String errorValve = getErrorReportValveClass();
            if ((errorValve != null) && (!errorValve.equals(""))) {
                try {
                    boolean found = false;
                    Valve[] valves = getPipeline().getValves();
                    for (Valve valve : valves) {
                        if (errorValve.equals(valve.getClass().getName())) {
                            found = true;
                            break;
                        }
                    }
                    if(!found) {   //检查管道有没有指定的Value,没有则添加
                        Valve valve =
                            (Valve) Class.forName(errorValve).getDeclaredConstructor().newInstance();
                        getPipeline().addValve(valve);
                    }
                } catch (Throwable t) {
                    ExceptionUtils.handleThrowable(t);
                    log.error(sm.getString(
                            "standardHost.invalidErrorReportValveClass",
                            errorValve), t);
                }
            }
            super.startInternal();
        }

**HostConfig类:**

package org.apache.catalina.startup;

public class HostConfig implements LifecycleListener

![70 5][]

public interface LifecycleListener {
    
    
        /**
         * Acknowledge the occurrence of the specified event.
         *
         * @param event LifecycleEvent that has occurred
         */
        public void lifecycleEvent(LifecycleEvent event);
    
    
    }

![70 6][]

HostConfig的start方法在 ContainerBase类的backgroundProcess()方法有一个

fireLifecycleEvent(Lifecycle.PERIODIC\_EVENT, null);方法调用

org.apache.catalina.startup.HostConfig
    
    /**
         * Process the START event for an associated Host.
         *
         * @param event The lifecycle event that has occurred
         */
        @Override
        public void lifecycleEvent(LifecycleEvent event) {
    
            // Identify the host we are associated with
            try {
                host = (Host) event.getLifecycle();
                if (host instanceof StandardHost) {
                    setCopyXML(((StandardHost) host).isCopyXML());
                    setDeployXML(((StandardHost) host).isDeployXML());
                    setUnpackWARs(((StandardHost) host).isUnpackWARs());
                    setContextClass(((StandardHost) host).getContextClass());
                }
            } catch (ClassCastException e) {
                log.error(sm.getString("hostConfig.cce", event.getLifecycle()), e);
                return;
            }
    
            // Process the event that has occurred
            if (event.getType().equals(Lifecycle.PERIODIC_EVENT)) {
                check();
            } else if (event.getType().equals(Lifecycle.BEFORE_START_EVENT)) {
                beforeStart();
            } else if (event.getType().equals(Lifecycle.START_EVENT)) {
                start();
            } else if (event.getType().equals(Lifecycle.STOP_EVENT)) {
                stop();
            }
        }

HostConfig类的lifecycleEvent方法在接收到Lifecycle.START\_EVENT时会调用start方法：

HostConfig的start()方法：

org.apache.catalina.HostConfig类：
 /**
 * Process a "start" event for this Host.
 */
 public void start() {
 
 if (log.isDebugEnabled())
 log.debug(sm.getString("hostConfig.start"));
 
 try {
 ObjectName hostON = host.getObjectName();
 oname = new ObjectName
 (hostON.getDomain() + ":type=Deployer,host=" + host.getName());
 Registry.getRegistry(null, null).registerComponent
 (this, oname, this.getClass().getName());
 } catch (Exception e) {
 log.error(sm.getString("hostConfig.jmx.register", oname), e);
 }
 
 if (!host.getAppBaseFile().isDirectory()) {
 log.error(sm.getString("hostConfig.appBase", host.getName(),
 host.getAppBaseFile().getPath()));
 host.setDeployOnStartup(false);
 host.setAutoDeploy(false);
 }
 
 if (host.getDeployOnStartup())
 deployApps();
 
 }
 
 
 /**
 * Deploy applications for any directories or WAR files that are found
 * in our "application root" directory.
 */
 protected void deployApps() {
 
 File appBase = host.getAppBaseFile();
 File configBase = host.getConfigBaseFile();
 String[] filteredAppPaths = filterAppPaths(appBase.list());
 // Deploy XML descriptors from configBase //部署xml描述文件
 //xml文件指的是conf/(enginename)/(hostname)/*.xml
 deployDescriptors(configBase, configBase.list());
 // Deploy WARs //部署war文件,站点目录下
 deployWARs(appBase, filteredAppPaths);
 // Deploy expanded folders //部署文件夹
 deployDirectories(appBase, filteredAppPaths);
 
 }
 
 /**
 * Deploy WAR files.
 */
 protected void deployWARs(File appBase, String[] files) {
 
 if (files == null)
 return;
 
 ExecutorService es = host.getStartStopExecutor();
 List<Future<?>> results = new ArrayList<>();
 
 for (int i = 0; i < files.length; i++) {
 
 if (files[i].equalsIgnoreCase("META-INF"))
 continue;
 if (files[i].equalsIgnoreCase("WEB-INF"))
 continue;
 File war = new File(appBase, files[i]);
 if (files[i].toLowerCase(Locale.ENGLISH).endsWith(".war") &&
 war.isFile() && !invalidWars.contains(files[i]) ) {
 
 ContextName cn = new ContextName(files[i], true);
 
 if (isServiced(cn.getName())) {
 continue;
 }
 if (deploymentExists(cn.getName())) {
 DeployedApplication app = deployed.get(cn.getName());
 boolean unpackWAR = unpackWARs;
 if (unpackWAR && host.findChild(cn.getName()) instanceof StandardContext) {
 unpackWAR = ((StandardContext) host.findChild(cn.getName())).getUnpackWAR();
 }
 if (!unpackWAR && app != null) {
 // Need to check for a directory that should not be
 // there
 File dir = new File(appBase, cn.getBaseName());
 if (dir.exists()) {
 if (!app.loggedDirWarning) {
 log.warn(sm.getString(
 "hostConfig.deployWar.hiddenDir",
 dir.getAbsoluteFile(),
 war.getAbsoluteFile()));
 app.loggedDirWarning = true;
 }
 } else {
 app.loggedDirWarning = false;
 }
 }
 continue;
 }
 
 // Check for WARs with /../ /./ or similar sequences in the name
 if (!validateContextPath(appBase, cn.getBaseName())) {
 log.error(sm.getString(
 "hostConfig.illegalWarName", files[i]));
 invalidWars.add(files[i]);
 continue;
 }
 
 results.add(es.submit(new DeployWar(this, cn, war)));
 }
 }
 
 for (Future<?> result : results) {
 try {
 result.get();
 } catch (Exception e) {
 log.error(sm.getString(
 "hostConfig.deployWar.threaded.error"), e);
 }
 }
 }

以上代码，HostConfig类start会检查Host站点配置的目录位置是否存在，调用deployApps部署。

**Context:**

org.apache.catalina.core.standardContext 
 
 /**
 * Start this component and implement the requirements
 * of {@link org.apache.catalina.util.LifecycleBase#startInternal()}.
 *
 * @exception LifecycleException if this component detects a fatal error
 * that prevents this component from being used
 */
 @Override
 protected synchronized void startInternal() throws LifecycleException {
 
 if(log.isDebugEnabled())
 log.debug("Starting " + getBaseName());
 
 // Send j2ee.state.starting notification //发送j2ee.state.starting的通知
 if (this.getObjectName() != null) {
 Notification notification = new Notification("j2ee.state.starting",
 this.getObjectName(), sequenceNumber.getAndIncrement());
 broadcaster.sendNotification(notification);
 }
 
 setConfigured(false);
 boolean ok = true;
 
 // Currently this is effectively a NO-OP but needs to be called to
 // ensure the NamingResources follows the correct lifecycle
 if (namingResources != null) {
 namingResources.start();
 }
 
 // Post work directory
 postWorkDirectory(); //设置工作目录等信息到Context中
 
 // Add missing components as necessary
 if (getResources() == null) { // (1) Required by Loader
 if (log.isDebugEnabled())
 log.debug("Configuring default Resources");
 
 try {// //这里的setResources指的是WebResourceRoot resources
 setResources(new StandardRoot(this)); 
 } catch (IllegalArgumentException e) {
 log.error(sm.getString("standardContext.resourcesInit"), e);
 ok = false;
 }
 }
 if (ok) {
 resourcesStart();
 }
 
 if (getLoader() == null) {
 WebappLoader webappLoader = new WebappLoader(getParentClassLoader());
 webappLoader.setDelegate(getDelegate());
 setLoader(webappLoader);
 }
 
 // An explicit cookie processor hasn't been specified; use the default
 if (cookieProcessor == null) {
 cookieProcessor = new LegacyCookieProcessor();
 }
 
 // Initialize character set mapper
 getCharsetMapper();
 
 // Validate required extensions
 boolean dependencyCheck = true;
 try {
 dependencyCheck = ExtensionValidator.validateApplication
 (getResources(), this);
 } catch (IOException ioe) {
 log.error(sm.getString("standardContext.extensionValidationError"), ioe);
 dependencyCheck = false;
 }
 
 if (!dependencyCheck) {
 // do not make application available if dependency check fails
 ok = false;
 }
 
 // Reading the "catalina.useNaming" environment variable
 String useNamingProperty = System.getProperty("catalina.useNaming");
 if ((useNamingProperty != null)
 && (useNamingProperty.equals("false"))) {
 useNaming = false;
 }
 
 if (ok && isUseNaming()) {
 if (getNamingContextListener() == null) {
 NamingContextListener ncl = new NamingContextListener();
 ncl.setName(getNamingContextName());
 ncl.setExceptionOnFailedWrite(getJndiExceptionOnFailedWrite());
 addLifecycleListener(ncl);
 setNamingContextListener(ncl);
 }
 }
 
 // Standard container startup
 if (log.isDebugEnabled())
 log.debug("Processing standard container startup");
 
 
 // Binding thread
 ClassLoader oldCCL = bindThread();
 
 try {
 if (ok) {
 // Start our subordinate components, if any
 Loader loader = getLoader();
 if ((loader != null) && (loader instanceof Lifecycle))
 ((Lifecycle) loader).start();
 
 // since the loader just started, the webapp classloader is now
 // created.
 setClassLoaderProperty("clearReferencesRmiTargets",
 getClearReferencesRmiTargets());
 setClassLoaderProperty("clearReferencesStatic",
 getClearReferencesStatic());
 setClassLoaderProperty("clearReferencesStopThreads",
 getClearReferencesStopThreads());
 setClassLoaderProperty("clearReferencesStopTimerThreads",
 getClearReferencesStopTimerThreads());
 setClassLoaderProperty("clearReferencesHttpClientKeepAliveThread",
 getClearReferencesHttpClientKeepAliveThread());
 setClassLoaderProperty("clearReferencesObjectStreamClassCaches",
 getClearReferencesObjectStreamClassCaches());
 
 // By calling unbindThread and bindThread in a row, we setup the
 // current Thread CCL to be the webapp classloader
 unbindThread(oldCCL);
 oldCCL = bindThread();
 
 // Initialize logger again. Other components might have used it
 // too early, so it should be reset.
 logger = null;
 getLogger();
 
 Realm realm = getRealmInternal();
 
 if (realm != null) {
 if (realm instanceof Lifecycle)
 ((Lifecycle) realm).start();
 
 // Place the CredentialHandler into the ServletContext so
 // applications can have access to it. Wrap it in a "safe"
 // handler so application's can't modify it.
 CredentialHandler safeHandler = new CredentialHandler() {
 @Override
 public boolean matches(String inputCredentials, String storedCredentials) {
 return getRealmInternal().getCredentialHandler().matches(inputCredentials, storedCredentials);
 }
 
 @Override
 public String mutate(String inputCredentials) {
 return getRealmInternal().getCredentialHandler().mutate(inputCredentials);
 }
 };
 context.setAttribute(Globals.CREDENTIAL_HANDLER, safeHandler);
 }
 
 // Notify our interested LifecycleListeners
 fireLifecycleEvent(Lifecycle.CONFIGURE_START_EVENT, null);
 
 // Start our child containers, if not already started
 for (Container child : findChildren()) {
 if (!child.getState().isAvailable()) {
 child.start();
 }
 }
 
 // Start the Valves in our pipeline (including the basic),
 // if any
 if (pipeline instanceof Lifecycle) {
 ((Lifecycle) pipeline).start();
 }
 
 // Acquire clustered manager
 Manager contextManager = null;
 Manager manager = getManager();
 if (manager == null) {
 if (log.isDebugEnabled()) {
 log.debug(sm.getString("standardContext.cluster.noManager",
 Boolean.valueOf((getCluster() != null)),
 Boolean.valueOf(distributable)));
 }
 if ( (getCluster() != null) && distributable) {
 try {
 contextManager = getCluster().createManager(getName());
 } catch (Exception ex) {
 log.error("standardContext.clusterFail", ex);
 ok = false;
 }
 } else {
 contextManager = new StandardManager();
 }
 }
 
 // Configure default manager if none was specified
 if (contextManager != null) {
 if (log.isDebugEnabled()) {
 log.debug(sm.getString("standardContext.manager",
 contextManager.getClass().getName()));
 }
 setManager(contextManager);
 }
 
 if (manager!=null && (getCluster() != null) && distributable) {
 //let the cluster know that there is a context that is distributable
 //and that it has its own manager
 getCluster().registerManager(manager);
 }
 }
 
 if (!getConfigured()) {
 log.error(sm.getString("standardContext.configurationFail"));
 ok = false;
 }
 
 // We put the resources into the servlet context
 if (ok)
 getServletContext().setAttribute
 (Globals.RESOURCES_ATTR, getResources());
 
 if (ok ) {
 if (getInstanceManager() == null) {
 javax.naming.Context context = null;
 if (isUseNaming() && getNamingContextListener() != null) {
 context = getNamingContextListener().getEnvContext();
 }
 Map<String, Map<String, String>> injectionMap = buildInjectionMap(
 getIgnoreAnnotations() ? new NamingResourcesImpl(): getNamingResources());
 setInstanceManager(new DefaultInstanceManager(context,
 injectionMap, this, this.getClass().getClassLoader()));
 getServletContext().setAttribute(
 InstanceManager.class.getName(), getInstanceManager());
 }
 }
 
 // Create context attributes that will be required
 if (ok) {
 getServletContext().setAttribute(
 JarScanner.class.getName(), getJarScanner());
 }
 
 // Set up the context init params
 mergeParameters();
 
 // Call ServletContainerInitializers
 for (Map.Entry<ServletContainerInitializer, Set<Class<?>>> entry :
 initializers.entrySet()) {
 try {
 entry.getKey().onStartup(entry.getValue(),
 getServletContext());
 } catch (ServletException e) {
 log.error(sm.getString("standardContext.sciFail"), e);
 ok = false;
 break;
 }
 }
 
 // Configure and call application event listeners
 if (ok) { //开始启动listener
 if (!listenerStart()) {
 log.error(sm.getString("standardContext.listenerFail"));
 ok = false;
 }
 }
 
 // Check constraints for uncovered HTTP methods
 // Needs to be after SCIs and listeners as they may programmatically
 // change constraints
 if (ok) {
 checkConstraintsForUncoveredMethods(findConstraints());
 }
 
 try {
 // Start manager
 Manager manager = getManager();
 if ((manager != null) && (manager instanceof Lifecycle)) {
 ((Lifecycle) manager).start();
 }
 } catch(Exception e) {
 log.error(sm.getString("standardContext.managerFail"), e);
 ok = false;
 }
 
 // Configure and call application filters
 if (ok) { //启动filter
 if (!filterStart()) {
 log.error(sm.getString("standardContext.filterFail"));
 ok = false;
 }
 }
 
 // Load and initialize all "load on startup" servlets
 if (ok) { //初始化Servlets
 if (!loadOnStartup(findChildren())){
 log.error(sm.getString("standardContext.servletFail"));
 ok = false;
 }
 }
 
 // Start ContainerBackgroundProcessor thread
 super.threadStart();
 } finally {
 // Unbinding thread
 unbindThread(oldCCL);
 }
 
 // Set available status depending upon startup success
 if (ok) {
 if (log.isDebugEnabled())
 log.debug("Starting completed");
 } else {
 log.error(sm.getString("standardContext.startFailed", getName()));
 }
 
 startTime=System.currentTimeMillis();
 
 // Send j2ee.state.running notification
 if (ok && (this.getObjectName() != null)) {
 Notification notification =
 new Notification("j2ee.state.running", this.getObjectName(),
 sequenceNumber.getAndIncrement());
 broadcaster.sendNotification(notification);
 }
 
 // The WebResources implementation caches references to JAR files. On
 // some platforms these references may lock the JAR files. Since web
 // application start is likely to have read from lots of JARs, trigger
 // a clean-up now.
 getResources().gc();
 
 // Reinitializing if something went wrong
 if (!ok) {
 setState(LifecycleState.FAILED);
 } else {
 setState(LifecycleState.STARTING);
 }
 }

1、namingResources.start();

NamingResourcesImpl继承自NameingResources,NamingResourcesImpl主要是管理j2EE命名的上下文和其关联的JNDI的上下文。

![70 7][]

NamingResourcesImpl类：
     @Override
        protected void startInternal() throws LifecycleException {
            fireLifecycleEvent(CONFIGURE_START_EVENT, null);
            setState(LifecycleState.STARTING);
        }

2、 resourcesStart();

![70 8][]

![70 9][]

resources.start();具体实现是在WebappClassLoaderBase类的start()方法里面。

WebappClassLoaderBase类的start() 主要是加载 WEB-INF/classes下的class和WEB-INF/lib下的class.

StandardContext类:
 
 private WebResourceRoot resources;
 /**
 * Allocate resources, including proxy.
 * Return <code>true</code> if initialization was successfull,
 * or <code>false</code> otherwise.
 */
 public void resourcesStart() throws LifecycleException {
 
 // Check current status in case resources were added that had already
 // been started
 if (!resources.getState().isAvailable()) {
 resources.start();
 }
 
 if (effectiveMajorVersion >=3 && addWebinfClassesResources) {
 WebResource webinfClassesResource = resources.getResource(
 "/WEB-INF/classes/META-INF/resources");
 if (webinfClassesResource.isDirectory()) {
 getResources().createWebResourceSet(
 WebResourceRoot.ResourceSetType.RESOURCE_JAR, "/",
 webinfClassesResource.getURL(), "/");
 }
 }
 }

org.apache.catalina.loader.WebappClassLoaderBase类
 /**
 * Repositories managed by this class rather than the super class.
 */
 private List<URL> localRepositories = new ArrayList<>();
 
 
 private volatile LifecycleState state = LifecycleState.NEW;
 private final HashMap<String,Long> jarModificationTimes = new HashMap<>();
 
 /**
 * Start the class loader.
 *
 * @exception LifecycleException if a lifecycle error occurs
 */
 @Override
 public void start() throws LifecycleException {
 
 state = LifecycleState.STARTING_PREP;
 
 WebResource classes = resources.getResource("/WEB-INF/classes");
 if (classes.isDirectory() && classes.canRead()) {
 localRepositories.add(classes.getURL());
 }
 WebResource[] jars = resources.listResources("/WEB-INF/lib");
 for (WebResource jar : jars) {
 if (jar.getName().endsWith(".jar") && jar.isFile() && jar.canRead()) {
 localRepositories.add(jar.getURL());
 jarModificationTimes.put(
 jar.getName(), Long.valueOf(jar.getLastModified()));
 }
 }
 
 state = LifecycleState.STARTING;
 
 String encoding = null;
 try {
 encoding = System.getProperty("file.encoding");
 } catch (SecurityException e) {
 return;
 }
 if (encoding.indexOf("EBCDIC")!=-1) {
 needConvert = true;
 }
 
 state = LifecycleState.STARTED;
 }

3、getCharsetMapper方法：

StandardContext类：
 
 /**
 * Return the Locale to character set mapper for this Context.
 */
 public CharsetMapper getCharsetMapper() {
 
 // Create a mapper the first time it is requested
 if (this.charsetMapper == null) {
 try {
 Class<?> clazz = Class.forName(charsetMapperClass);
 this.charsetMapper = (CharsetMapper) clazz.getDeclaredConstructor().newInstance();
 } catch (Throwable t) {
 ExceptionUtils.handleThrowable(t);
 this.charsetMapper = new CharsetMapper();
 }
 }
 
 return (this.charsetMapper);
 
 }

package org.apache.catalina.util;
    
    import java.io.InputStream;
    import java.util.Locale;
    import java.util.Properties;
    import org.apache.tomcat.util.ExceptionUtils;
    
    /**
     * Utility class that attempts to map from a Locale to the corresponding
     * character set to be used for interpreting input text (or generating
     * output text) when the Content-Type header does not include one.  You
     * can customize the behavior of this class by modifying the mapping data
     * it loads, or by subclassing it (to change the algorithm) and then using
     * your own version for a particular web application.
     *
     * @author Craig R. McClanahan
     */
    public class CharsetMapper {
    
    
        // ---------------------------------------------------- Manifest Constants
    
    
        /**
         * Default properties resource name.
         */
        public static final String DEFAULT_RESOURCE =
          "/org/apache/catalina/util/CharsetMapperDefault.properties";
    
        // ---------------------------------------------------------- Constructors
    
        /**
         * Construct a new CharsetMapper using the default properties resource.
         */
        public CharsetMapper() {
            this(DEFAULT_RESOURCE);
        }
        public CharsetMapper(String name) {
            try (InputStream stream = this.getClass().getResourceAsStream(name)) {
                map.load(stream);
            } catch (Throwable t) {
                ExceptionUtils.handleThrowable(t);
                throw new IllegalArgumentException(t.toString());
            }
        }
    
        // ---------------------------------------------------- Instance Variables
    
        private Properties map = new Properties();
    
        // ------------------------------------------------------- Public Methods
    
        public String getCharset(Locale locale) {
            // Match full language_country_variant first, then language_country,
            // then language only
            String charset = map.getProperty(locale.toString());
            if (charset == null) {
                charset = map.getProperty(locale.getLanguage() + "_"
                        + locale.getCountry());
                if (charset == null) {
                    charset = map.getProperty(locale.getLanguage());
                }
            }
            return (charset);
        }
    
        public void addCharsetMappingFromDeploymentDescriptor(String locale, String charset) {
            map.put(locale, charset);
        }
    
    
    }

4、ExtensionValidator.validateApplication(getResources(), this);方法

/**
 * Runtime validation of a Web Application.
 *
 * This method uses JNDI to look up the resources located under a
 * <code>DirContext</code>. It locates Web Application MANIFEST.MF
 * file in the /META-INF/ directory of the application and all
 * MANIFEST.MF files in each JAR file located in the WEB-INF/lib
 * directory and creates an <code>ArrayList</code> of
 * <code>ManifestResource</code> objects. These objects are then passed
 * to the validateManifestResources method for validation.
 *
 * @param resources The resources configured for this Web Application
 * @param context The context from which the Logger and path to the
 * application
 *
 * @return true if all required extensions satisfied
 */
 public static synchronized boolean validateApplication(
 WebResourceRoot resources,
 Context context)
 throws IOException {
 
 String appName = context.getName();
 ArrayList<ManifestResource> appManifestResources = new ArrayList<>();
 
 // Web application manifest
 WebResource resource = resources.getResource("/META-INF/MANIFEST.MF");
 if (resource.isFile()) {
 try (InputStream inputStream = resource.getInputStream()) {
 Manifest manifest = new Manifest(inputStream);
 ManifestResource mre = new ManifestResource
 (sm.getString("extensionValidator.web-application-manifest"),
 manifest, ManifestResource.WAR);
 appManifestResources.add(mre);
 }
 }
 
 // Web application library manifests
 WebResource[] manifestResources =
 resources.getClassLoaderResources("/META-INF/MANIFEST.MF");
 for (WebResource manifestResource : manifestResources) {
 if (manifestResource.isFile()) {
 // Primarily used for error reporting
 String jarName = manifestResource.getURL().toExternalForm();
 Manifest jmanifest = manifestResource.getManifest();
 if (jmanifest != null) {
 ManifestResource mre = new ManifestResource(jarName,
 jmanifest, ManifestResource.APPLICATION);
 appManifestResources.add(mre);
 }
 }
 }
 
 return validateManifestResources(appName, appManifestResources);
 }

主要是校验/META-INF/MANIFEST.MF文件里面的信息。

/META-INF/MANIFEST.MF文件内容示例如下：

![70 10][]

5、Realm--> CredentialHandler safeHandler = new CredentialHandler()

安全域，主要验证平局是否可以授权进入 这个ServletContext,是否是安全的。（Credential：凭据）

Realm realm = getRealmInternal();
    
                    if (realm != null) {
                        if (realm instanceof Lifecycle)
                            ((Lifecycle) realm).start();
    
                        // Place the CredentialHandler into the ServletContext so
                        // applications can have access to it. Wrap it in a "safe"
                        // handler so application's can't modify it.
                        CredentialHandler safeHandler = new CredentialHandler() {
                            @Override
                            public boolean matches(String inputCredentials, String storedCredentials) {
                                return getRealmInternal().getCredentialHandler().matches(inputCredentials, storedCredentials);
                            }
    
                            @Override
                            public String mutate(String inputCredentials) {
                                return getRealmInternal().getCredentialHandler().mutate(inputCredentials);
                            }
                        };
                        context.setAttribute(Globals.CREDENTIAL_HANDLER, safeHandler);
                    }

6、mergeParameters()方法合并context的初始化参数

/**
 * Merge the context initialization parameters specified in the application
 * deployment descriptor with the application parameters described in the
 * server configuration, respecting the <code>override</code> property of
 * the application parameters appropriately.
 */
 private void mergeParameters() {
 Map<String,String> mergedParams = new HashMap<>();
 
 String names[] = findParameters();
 for (int i = 0; i < names.length; i++) {
 mergedParams.put(names[i], findParameter(names[i]));
 }
 
 ApplicationParameter params[] = findApplicationParameters();
 for (int i = 0; i < params.length; i++) {
 if (params[i].getOverride()) {
 if (mergedParams.get(params[i].getName()) == null) {
 mergedParams.put(params[i].getName(),
 params[i].getValue());
 }
 } else {
 mergedParams.put(params[i].getName(), params[i].getValue());
 }
 }
 
 ServletContext sc = getServletContext();
 for (Map.Entry<String,String> entry : mergedParams.entrySet()) {
 sc.setInitParameter(entry.getKey(), entry.getValue());
 }
 
 }

7、listenerStart()方法

StandardContext类：
 /**
 * Configure the set of instantiated application event listeners
 * for this Context. Return <code>true</code> if all listeners wre
 * initialized successfully, or <code>false</code> otherwise.
 */
 public boolean listenerStart() {
 
 if (log.isDebugEnabled())
 log.debug("Configuring application event listeners");
 
 // Instantiate the required listeners
 String listeners[] = findApplicationListeners();
 Object results[] = new Object[listeners.length];
 boolean ok = true;
 for (int i = 0; i < results.length; i++) {
 if (getLogger().isDebugEnabled())
 getLogger().debug(" Configuring event listener class '" +
 listeners[i] + "'");
 try {
 String listener = listeners[i];
 results[i] = getInstanceManager().newInstance(listener);
 } catch (Throwable t) {
 t = ExceptionUtils.unwrapInvocationTargetException(t);
 ExceptionUtils.handleThrowable(t);
 getLogger().error(sm.getString(
 "standardContext.applicationListener", listeners[i]), t);
 ok = false;
 }
 }
 if (!ok) {
 getLogger().error(sm.getString("standardContext.applicationSkipped"));
 return (false);
 }
 
 // Sort listeners in two arrays
 ArrayList<Object> eventListeners = new ArrayList<>();
 ArrayList<Object> lifecycleListeners = new ArrayList<>();
 for (int i = 0; i < results.length; i++) {
 if ((results[i] instanceof ServletContextAttributeListener)
 || (results[i] instanceof ServletRequestAttributeListener)
 || (results[i] instanceof ServletRequestListener)
 || (results[i] instanceof HttpSessionIdListener)
 || (results[i] instanceof HttpSessionAttributeListener)) {
 eventListeners.add(results[i]);
 }
 if ((results[i] instanceof ServletContextListener)
 || (results[i] instanceof HttpSessionListener)) {
 lifecycleListeners.add(results[i]);
 }
 }
 
 // Listener instances may have been added directly to this Context by
 // ServletContextInitializers and other code via the pluggability APIs.
 // Put them these listeners after the ones defined in web.xml and/or
 // annotations then overwrite the list of instances with the new, full
 // list.
 for (Object eventListener: getApplicationEventListeners()) {
 eventListeners.add(eventListener);
 }
 setApplicationEventListeners(eventListeners.toArray());
 for (Object lifecycleListener: getApplicationLifecycleListeners()) {
 lifecycleListeners.add(lifecycleListener);
 if (lifecycleListener instanceof ServletContextListener) {
 noPluggabilityListeners.add(lifecycleListener);
 }
 }
 setApplicationLifecycleListeners(lifecycleListeners.toArray());
 
 // Send application start events
 
 if (getLogger().isDebugEnabled())
 getLogger().debug("Sending application start events");
 
 // Ensure context is not null
 getServletContext();
 context.setNewServletContextListenerAllowed(false);
 
 Object instances[] = getApplicationLifecycleListeners();
 if (instances == null || instances.length == 0) {
 return ok;
 }
 
 ServletContextEvent event = new ServletContextEvent(getServletContext());
 ServletContextEvent tldEvent = null;
 if (noPluggabilityListeners.size() > 0) {
 noPluggabilityServletContext = new NoPluggabilityServletContext(getServletContext());
 tldEvent = new ServletContextEvent(noPluggabilityServletContext);
 }
 for (int i = 0; i < instances.length; i++) {
 if (!(instances[i] instanceof ServletContextListener))
 continue;
 ServletContextListener listener =
 (ServletContextListener) instances[i];
 try {
 fireContainerEvent("beforeContextInitialized", listener);
 if (noPluggabilityListeners.contains(listener)) {
 listener.contextInitialized(tldEvent);
 } else {
 listener.contextInitialized(event);
 }
 fireContainerEvent("afterContextInitialized", listener);
 } catch (Throwable t) {
 ExceptionUtils.handleThrowable(t);
 fireContainerEvent("afterContextInitialized", listener);
 getLogger().error
 (sm.getString("standardContext.listenerStart",
 instances[i].getClass().getName()), t);
 ok = false;
 }
 }
 return (ok);
 
 }

8、checkConstraintsForUncoveredMethods(findConstraints());

StandardContext类：
    
     private void checkConstraintsForUncoveredMethods(
                SecurityConstraint[] constraints) {
            SecurityConstraint[] newConstraints =
                    SecurityConstraint.findUncoveredHttpMethods(constraints,
                            getDenyUncoveredHttpMethods(), getLogger());
            for (SecurityConstraint constraint : newConstraints) {
                addConstraint(constraint);
            }
        }

而SecurityConstraint表示WEB应用程序的安全性约束，

就是<security-constraint> 描述文件 所配置的那样。<http-method>是<security-constraint> 子元素.

如果没有 <http-method> 元素，这表示将禁止所有 HTTP 方法访问相应的资源。

<security-constraint> 
 <display-name>porject</display-name> 
 <web-resource-collection> 
 <web-resource-name>baseproject</web-resource-name> 
 <url-pattern>*.jsp</url-pattern> 
 <url-pattern>*.do</url-pattern> 
 <http-method>GET</http-method> 
 <http-method>HEAD</http-method> 
 <http-method>TRACE</http-method> 
 <http-method>POST</http-method> 
 <http-method>DELETE</http-method> 
 <http-method>OPTIONS</http-method> 
 </web-resource-collection> 
 <auth-constraint> 
 <description>porject</description> 
 <role-name>All Role</role-name> 
 </auth-constraint> 
 <user-data-constraint> 
 <transport-guarantee>NONE</transport-guarantee> 
 </user-data-constraint> 
 </security-constraint>

一个是对该url-pattern进行了role的限制，即配置auth-constraint了
 
 <security-constraint>
 <web-resource-collection>
 <web-resource-name>tests</web-resource-name>
 <url-pattern>/*</url-pattern>
 </web-resource-collection>
 <auth-constraint> //增加了这个就表示对访问/*有角色访问限制
 <role-name>role</role-name>
 </auth-constraint>
 </security-constraint>

9、filterStart()方法：

StandardContext类： 
 
 /**
 * Configure and initialize the set of filters for this Context.
 * Return <code>true</code> if all filter initialization completed
 * successfully, or <code>false</code> otherwise.
 */
 public boolean filterStart() {
 
 if (getLogger().isDebugEnabled()) {
 getLogger().debug("Starting filters");
 }
 // Instantiate and record a FilterConfig for each defined filter
 boolean ok = true;
 synchronized (filterConfigs) {
 filterConfigs.clear();
 for (Entry<String,FilterDef> entry : filterDefs.entrySet()) {
 String name = entry.getKey();
 if (getLogger().isDebugEnabled()) {
 getLogger().debug(" Starting filter '" + name + "'");
 }
 try {
 ApplicationFilterConfig filterConfig =
 new ApplicationFilterConfig(this, entry.getValue());
 filterConfigs.put(name, filterConfig);
 } catch (Throwable t) {
 t = ExceptionUtils.unwrapInvocationTargetException(t);
 ExceptionUtils.handleThrowable(t);
 getLogger().error(sm.getString(
 "standardContext.filterStart", name), t);
 ok = false;
 }
 }
 }
 
 return ok;
 }

10、loadOnStartup()方法:

/**
 * Load and initialize all servlets marked "load on startup" in the
 * web application deployment descriptor.
 *
 * @param children Array of wrappers for all currently defined
 * servlets (including those not declared load on startup)
 */
 public boolean loadOnStartup(Container children[]) {
 
 // Collect "load on startup" servlets that need to be initialized
 TreeMap<Integer, ArrayList<Wrapper>> map = new TreeMap<>();
 for (int i = 0; i < children.length; i++) {
 Wrapper wrapper = (Wrapper) children[i];
 int loadOnStartup = wrapper.getLoadOnStartup();
 if (loadOnStartup < 0)
 continue;
 Integer key = Integer.valueOf(loadOnStartup);
 ArrayList<Wrapper> list = map.get(key);
 if (list == null) {
 list = new ArrayList<>();
 map.put(key, list);
 }
 list.add(wrapper);
 }
 
 // Load the collected "load on startup" servlets
 for (ArrayList<Wrapper> list : map.values()) {
 for (Wrapper wrapper : list) {
 try {
 wrapper.load();
 } catch (ServletException e) {
 getLogger().error(sm.getString("standardContext.loadOnStartup.loadException",
 getName(), wrapper.getName()), StandardWrapper.getRootCause(e));
 // NOTE: load errors (including a servlet that throws
 // UnavailableException from the init() method) are NOT
 // fatal to application startup
 // unless failCtxIfServletStartFails="true" is specified
 if(getComputedFailCtxIfServletStartFails()) {
 return false;
 }
 }
 }
 }
 return true;
 
 }

**Wrapper:**

StandardWrapper类:
     /**
         * Start this component and implement the requirements
         * of {@link org.apache.catalina.util.LifecycleBase#startInternal()}.
         *
         * @exception LifecycleException if this component detects a fatal error
         *  that prevents this component from being used
         */
        @Override
        protected synchronized void startInternal() throws LifecycleException {
    
            // Send j2ee.state.starting notification
            if (this.getObjectName() != null) {
                Notification notification = new Notification("j2ee.state.starting",
                                                            this.getObjectName(),
                                                            sequenceNumber++);
                broadcaster.sendNotification(notification);    //发送通知用于JMX
            }
    
            // Start up this component
            super.startInternal();
    
            setAvailable(0L);
    
            // Send j2ee.state.running notification
            if (this.getObjectName() != null) {
                Notification notification =
                    new Notification("j2ee.state.running", this.getObjectName(),
                                    sequenceNumber++);
                broadcaster.sendNotification(notification);  //发送通知用于JMX
            }
    
        }
    
    
        /**
         * Set the available date/time for this servlet, in milliseconds since the
         * epoch.  If this date/time is Long.MAX_VALUE, it is considered to mean
         * that unavailability is permanent and any request for this servlet will return
         * an SC_NOT_FOUND error. If this date/time is in the future, any request for
         * this servlet will return an SC_SERVICE_UNAVAILABLE error.
         *
         * @param available The new available date/time
         */
        @Override
        public void setAvailable(long available) {      //为servlet设置可用的时间
    
            long oldAvailable = this.available;
            if (available > System.currentTimeMillis())
                this.available = available;
            else
                this.available = 0L;
            support.firePropertyChange("available", Long.valueOf(oldAvailable),
                                       Long.valueOf(this.available));
    
        }

[70]: /images/20220514/f89caaddec1845d39bdcffdf1ce72d71.png
[70 1]: /images/20220514/d2e8e9089cf5405a809c564e39d9657f.png
[70 2]: /images/20220514/1826e3376b88499bb98cb4ca97bb3787.png
[70 3]: /images/20220514/ddeacb9cadd5481bbf5812da66d21532.png
[http_tomcat.apache.org_tomcat-7.0-doc_config_globalresources.html]: http://tomcat.apache.org/tomcat-7.0-doc/config/globalresources.html
[https_blog.csdn.net_conquer0715_article_details_78206874_locationNum_6_fps_1]: https://blog.csdn.net/conquer0715/article/details/78206874?locationNum=6&fps=1
[70 4]: /images/20220514/cf84c78840e945d8b599ef294d0a80e2.png
[70 5]: /images/20220514/9a3e7cea4f08488baa3c6b5766517125.png
[70 6]: /images/20220514/b1c9ff0705844cb18028069580ab6145.png
[70 7]: /images/20220514/ed35bc91024a41aaa3ed0fd198898430.png
[70 8]: /images/20220514/35e6ec04ffaa4931b94fcce7b9cbaf05.png
[70 9]: /images/20220514/7f0e1e6c7870459188e2e1425d23bd0d.png
[70 10]: /images/20220514/90ec54a314f1406a90d58bbb913cd75b.png