理解思路第一类比StandardServer, 抓住StandardService整体类依赖结构来理解第二结合server.xml中service配置来理解见下文具体阐述。第三结合Service Config官方配置文档http://tomcat.apache.org/tomcat-9.0-doc/config/service.htmlService结构设计我们需要从高一点的维度去理解service的结构设计而不是多少方法多少代码这里的理解一定是要结合Server.xml中service配置部分对应理解。server.xml首先要看下server.xml中Service的配置这样你便知道了需要了解的4个部分!-- 每个Service元素只能有一个Engine元素.元素处理在同一个Service中所有Connector元素接收到的客户请求 -- Service nameCatalina !-- 1. 属性说明 name:Service的名称 -- !--2. 一个或多个excecutors -- !-- Executor nametomcatThreadPool namePrefixcatalina-exec- maxThreads150 minSpareThreads4/ -- !-- 3.Connector元素: 由Connector接口定义.Connector元素代表与客户程序实际交互的组件,它负责接收客户请求,以及向客户返回响应结果. -- Connector port80 maxHttpHeaderSize8192 maxThreads150 minSpareThreads25 maxSpareThreads75 enableLookupsfalse redirectPort8443 acceptCount100 connectionTimeout20000 disableUploadTimeouttrue / !-- 属性说明 port:服务器连接器的端口号,该连接器将在指定端口侦听来自客户端的请求。 enableLookups:如果为true则可以通过调用request.getRemoteHost()进行DNS查询来得到远程客户端的实际主机名 若为false则不进行DNS查询而是返回其ip地址。 redirectPort:服务器正在处理http请求时收到了一个SSL传输请求后重定向的端口号。 acceptCount:当所有可以使用的处理请求的线程都被用光时,可以放到处理队列中的请求数,超过这个数的请求将不予处理而返回Connection refused错误。 connectionTimeout:等待超时的时间数以毫秒为单位。 maxThreads:设定在监听端口的线程的最大数目,这个值也决定了服务器可以同时响应客户请求的最大数目.默认值为200。 protocol:必须设定为AJP/1.3协议。 address:如果服务器有两个以上IP地址,该属性可以设定端口监听的IP地址,默认情况下,端口会监听服务器上所有IP地址。 minProcessors:服务器启动时创建的处理请求的线程数每个请求由一个线程负责。 maxProcessors:最多可以创建的处理请求的线程数。 minSpareThreads:最小备用线程 。 maxSpareThreads:最大备用线程。 debug:日志等级。 disableUploadTimeout:禁用上传超时,主要用于大数据上传时。 -- Connector port8009 enableLookupsfalse redirectPort8443 protocolAJP/1.3 / !-- 负责和其他HTTP服务器建立连接。在把Tomcat与其他HTTP服务器集成时就需要用到这个连接器。 -- !-- 4. Engine -- Engine nameCatalina defaultHostlocalhost /Engine /ServiceService中的接口设计公共属性, name等/** * return the name of this Service. */ public String getName(); /** * Set the name of this Service. * * param name The new service name */ public void setName(String name);父Server相关/** * return the codeServer/code with which we are associated (if any). */ public Server getServer(); /** * Set the codeServer/code with which we are associated (if any). * * param server The server that owns this Service */ public void setServer(Server server); /** * return the parent class loader for this component. If not set, return * {link #getServer()} {link Server#getParentClassLoader()}. If no server * has been set, return the system class loader. */ public ClassLoader getParentClassLoader(); /** * Set the parent class loader for this service. * * param parent The new parent class loader */ public void setParentClassLoader(ClassLoader parent); /** * return the domain under which this container will be / has been * registered. */ public String getDomain();Connector相关/** * Add a new Connector to the set of defined Connectors, and associate it * with this Services Container. * * param connector The Connector to be added */ public void addConnector(Connector connector); /** * Find and return the set of Connectors associated with this Service. * * return the set of associated Connectors */ public Connector[] findConnectors(); /** * Remove the specified Connector from the set associated from this * Service. The removed Connector will also be disassociated from our * Container. * * param connector The Connector to be removed */ public void removeConnector(Connector connector);Engine/** * return the codeEngine/code that handles requests for all * codeConnectors/code associated with this Service. */ public Engine getContainer(); /** * Set the codeEngine/code that handles requests for all * codeConnectors/code associated with this Service. * * param engine The new Engine */ public void setContainer(Engine engine);Excutor相关/** * Adds a named executor to the service * param ex Executor */ public void addExecutor(Executor ex); /** * Retrieves all executors * return Executor[] */ public Executor[] findExecutors(); /** * Retrieves executor by name, null if not found * param name String * return Executor */ public Executor getExecutor(String name); /** * Removes an executor from the service * param ex Executor */ public void removeExecutor(Executor ex);StandardService的实现属性和父Server相关比较简单这里主要看下其它的方法Engine相关private Engine engine null; Override public Engine getContainer() { return engine; } Override public void setContainer(Engine engine) { Engine oldEngine this.engine; if (oldEngine ! null) { oldEngine.setService(null); } this.engine engine; if (this.engine ! null) { this.engine.setService(this); } if (getState().isAvailable()) { if (this.engine ! null) { try { this.engine.start(); // 启动Engine } catch (LifecycleException e) { log.error(sm.getString(standardService.engine.startFailed), e); } } // 重启Mapper - Restart MapperListener to pick up new engine. try { mapperListener.stop(); } catch (LifecycleException e) { log.error(sm.getString(standardService.mapperListener.stopFailed), e); } try { mapperListener.start(); } catch (LifecycleException e) { log.error(sm.getString(standardService.mapperListener.startFailed), e); } if (oldEngine ! null) { try { oldEngine.stop(); } catch (LifecycleException e) { log.error(sm.getString(standardService.engine.stopFailed), e); } } } // 触发container属性变更事件 support.firePropertyChange(container, oldEngine, this.engine); }Connectors相关/** * The set of Connectors associated with this Service. */ protected Connector connectors[] new Connector[0]; private final Object connectorsLock new Object(); /** * Add a new Connector to the set of defined Connectors, and associate it * with this Services Container. * * param connector The Connector to be added */ Override public void addConnector(Connector connector) { synchronized (connectorsLock) { connector.setService(this); Connector results[] new Connector[connectors.length 1]; System.arraycopy(connectors, 0, results, 0, connectors.length); results[connectors.length] connector; connectors results; } try { if (getState().isAvailable()) { connector.start(); } } catch (LifecycleException e) { throw new IllegalArgumentException( sm.getString(standardService.connector.startFailed, connector), e); } // Report this property change to interested listeners support.firePropertyChange(connector, null, connector); } public ObjectName[] getConnectorNames() { ObjectName results[] new ObjectName[connectors.length]; for (int i0; iresults.length; i) { results[i] connectors[i].getObjectName(); } return results; } /** * 当前Service相关的所有Connectors. */ Override public Connector[] findConnectors() { return connectors; } /** * 删除connector * * param connector The Connector to be removed */ Override public void removeConnector(Connector connector) { synchronized (connectorsLock) { // 找到conector位置 int j -1; for (int i 0; i connectors.length; i) { if (connector connectors[i]) { j i; break; } } if (j 0) return; if (connectors[j].getState().isAvailable()) { try { connectors[j].stop(); // 停止 } catch (LifecycleException e) { log.error(sm.getString( standardService.connector.stopFailed, connectors[j]), e); } } connector.setService(null); // 去除父service绑定 int k 0; Connector results[] new Connector[connectors.length - 1]; for (int i 0; i connectors.length; i) { if (i ! j) results[k] connectors[i]; // 后续connector向前移位 } connectors results; // 触发connector属性变更事件 support.firePropertyChange(connector, connector, null); } }Executor相关CRUD方法代码比较简单/** * Adds a named executor to the service * param ex Executor */ Override public void addExecutor(Executor ex) { synchronized (executors) { if (!executors.contains(ex)) { executors.add(ex); if (getState().isAvailable()) { try { ex.start(); // 启动 } catch (LifecycleException x) { log.error(sm.getString(standardService.executor.start), x); } } } } } /** * Retrieves all executors * return Executor[] */ Override public Executor[] findExecutors() { synchronized (executors) { Executor[] arr new Executor[executors.size()]; executors.toArray(arr); return arr; } } /** * Retrieves executor by name, null if not found * param executorName String * return Executor */ Override public Executor getExecutor(String executorName) { synchronized (executors) { for (Executor executor: executors) { if (executorName.equals(executor.getName())) return executor; } } return null; } /** * Removes an executor from the service * param ex Executor */ Override public void removeExecutor(Executor ex) { synchronized (executors) { if ( executors.remove(ex) getState().isAvailable() ) { try { ex.stop(); // 停止 } catch (LifecycleException e) { log.error(sm.getString(standardService.executor.stop), e); } } } }Lifecycle相关模板方法首先看initInternal方法/** * Invoke a pre-startup initialization. This is used to allow connectors * to bind to restricted ports under Unix operating environments. */ Override protected void initInternal() throws LifecycleException { super.initInternal(); if (engine ! null) { engine.init(); } // Initialize any Executors for (Executor executor : findExecutors()) { if (executor instanceof JmxEnabled) { ((JmxEnabled) executor).setDomain(getDomain()); } executor.init(); } // Initialize mapper listener mapperListener.init(); // Initialize our defined Connectors synchronized (connectorsLock) { for (Connector connector : connectors) { connector.init(); } } }initInternal 代码很短思路也很清晰就是依次调用了这个成员变量的 init 方法engine.init() executor.init mapperListener.init() connector.init()startInternal 方法/** * Start nested components ({link Executor}s, {link Connector}s and * {link Container}s) 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 void startInternal() throws LifecycleException { if(log.isInfoEnabled()) log.info(sm.getString(standardService.start.name, this.name)); setState(LifecycleState.STARTING); // Start our defined Container first if (engine ! null) { synchronized (engine) { engine.start(); } } synchronized (executors) { for (Executor executor: executors) { executor.start(); } } mapperListener.start(); // Start our defined Connectors second synchronized (connectorsLock) { for (Connector connector: connectors) { // If it has already failed, dont try and start it if (connector.getState() ! LifecycleState.FAILED) { connector.start(); } } } }startInternal 跟 initInternal 方法一样也是依次调用engine.start(); executor.start(); mapperListener.start(); connector.start();补充下MapperListenermapperListener 的作用是在 start 的时候将容器类对象注册到 Mapper 对象中。/** * Create mapper listener. * * param service The service this listener is associated with */ public MapperListener(Service service) { this.service service; this.mapper service.getMapper(); } service.getMapper() 返回的是 StandardService 对象的 mapper 成员变量。 /** * Mapper. */ protected final Mapper mapper new Mapper();Mapper是 Tomcat 处理 Http 请求时非常重要的组件。Tomcat 使用 Mapper 来处理一个 Request 到 Host、Context 的映射关系从而决定使用哪个 Service 来处理请求。MapperListener 也是继承自 LifecycleMBeanBase不过没有重载 initInternal 方法。startInternal 方法Override public void startInternal() throws LifecycleException { setState(LifecycleState.STARTING); Engine engine service.getContainer(); if (engine null) { return; } findDefaultHost(); addListeners(engine); Container[] conHosts engine.findChildren(); for (Container conHost : conHosts) { Host host (Host) conHost; if (!LifecycleState.NEW.equals(host.getState())) { // Registering the host will register the context and wrappers registerHost(host); } } }findDefaultHost() 方法首先看 findDefaultHost() 方法private void findDefaultHost() { Engine engine service.getContainer(); String defaultHost engine.getDefaultHost(); boolean found false; if (defaultHost ! null defaultHost.length() 0) { Container[] containers engine.findChildren(); for (Container container : containers) { Host host (Host) container; if (defaultHost.equalsIgnoreCase(host.getName())) { found true; break; } String[] aliases host.findAliases(); for (String alias : aliases) { if (defaultHost.equalsIgnoreCase(alias)) { found true; break; } } } } if (found) { mapper.setDefaultHostName(defaultHost); } else { log.error(sm.getString(mapperListener.unknownDefaultHost, defaultHost, service)); } }findDefaultHost() 是主要是找出 defaultHost 并调用mapper.setDefaultHostName(defaultHost);这个 defaultHost 是 server.xml 的Engine标签的属性一般都是 localHost。从上面代码 for 代码块里可以看出Host 是 Engine 的子 Container。for 语句就是找出一个名字跟 defaultHost 指定的名字相同的 Host 对象。addListeners(engine) 方法/** * Add this mapper to the container and all child containers * * param container */ private void addListeners(Container container) { container.addContainerListener(this); container.addLifecycleListener(this); for (Container child : container.findChildren()) { addListeners(child); } }这个方法的作用是将 MapperListener 这个监听器添加到 Engine 及其子容器中registerHost 调用 registerHost方法来注册 Engine 的字容器 Host。/** * Register host. */ private void registerHost(Host host) { String[] aliases host.findAliases(); mapper.addHost(host.getName(), aliases, host); for (Container container : host.findChildren()) { if (container.getState().isAvailable()) { registerContext((Context) container); } } // Default host may have changed findDefaultHost(); if(log.isDebugEnabled()) { log.debug(sm.getString(mapperListener.registerHost, host.getName(), domain, service)); } }registerHost 方法先调用 mapper.addHost然后调用 registerContext 方法注册 Host 的子容器 Context。 mapper.addHost 方法是将 Host 加入的 Mapper 类的的成员变量MappedHost[] hosts 中。接着看 registerContext 方法/** * Register context. */ private void registerContext(Context context) { String contextPath context.getPath(); if (/.equals(contextPath)) { contextPath ; } Host host (Host)context.getParent(); WebResourceRoot resources context.getResources(); String[] welcomeFiles context.findWelcomeFiles(); ListWrapperMappingInfo wrappers new ArrayList(); for (Container container : context.findChildren()) { prepareWrapperMappingInfo(context, (Wrapper) container, wrappers); if(log.isDebugEnabled()) { log.debug(sm.getString(mapperListener.registerWrapper, container.getName(), contextPath, service)); } } mapper.addContextVersion(host.getName(), host, contextPath, context.getWebappVersion(), context, welcomeFiles, resources, wrappers); if(log.isDebugEnabled()) { log.debug(sm.getString(mapperListener.registerContext, contextPath, service)); } }registerContext 里先获取一些对象比如 WebResourceRoot 对象、WrapperMappingInfo 对象然后调用 mapper.addContextVersion。Mapper#addContextVersion 方法比较琐细就不细讲了。其主要逻辑是将 Context 对象以及 Context 的子容器 Wrapper 对象每一个都分别构建一个对应的 MappedContext 和 MappedWrapper 对象然后把 MappedContext 和 MappedWrapper 塞进 ContextVersion 对象中最后把 Context 和 ContextVersion 的对应关系放在 Mapper 对象的一个 Map 里。这里的 MappedContext 和 MappedWrapper 在 Tomcat 处理 Http 请求的时候是比较关键的。registerHost 最后再更新了一下可能发生改变里的的 defaultHost。