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类比StandardServer, 抓住StandardService整体类依赖结构来理解

news 2026/7/2 3:26:22

ervice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

xml

<!-- 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 name="Catalina"> <!-- 1. 属性说明 name:Service的名称 --> <!--2. 一个或多个excecutors --> <!-- <Executor name="tomcatThreadPool" namePrefix="catalina-exec-" maxThreads="150" minSpareThreads="4"/> --> <!-- 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 port="80" maxHttpHeaderSize="8192" maxThreads="150" minSpareThreads="25" maxSpareThreads="75" enableLookups="false" redirectPort="8443" acceptCount="100" connectionTimeout="20000" disableUploadTimeout="true" /> <!-- 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 port="8009" enableLookups="false" redirectPort="8443" protocol="AJP/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 name="Catalina" defaultHost="localhost"> </Engine> </Service>

Service中的接口设计

  • 公共属性, name等

java

/** * @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

java

/** * @return the <code>Server</code> with which we are associated (if any). */ public Server getServer(); /** * Set the <code>Server</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

java

/** * Add a new Connector to the set of defined Connectors, and associate it * with this Service's 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

java

/** * @return the <code>Engine</code> that handles requests for all * <code>Connectors</code> associated with this Service. */ public Engine getContainer(); /** * Set the <code>Engine</code> that handles requests for all * <code>Connectors</code> associated with this Service. * * @param engine The new Engine */ public void setContainer(Engine engine);
  • Excutor相关

java

/** * 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

java

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

java

/** * 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 Service's 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 i=0; i<results.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

java

/** * 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

java

/** * 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

java

engine.init() executor.init mapperListener.init() connector.init()

startInternal 方法

java

/** * 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, don't try and start it if (connector.getState() != LifecycleState.FAILED) { connector.start(); } } } }

startInternal 跟 initInternal 方法一样，也是依次调用

java

engine.start(); executor.start(); mapperListener.start(); connector.start();

补充下MapperListener

mapperListener 的作用是在 start 的时候将容器类对象注册到 Mapper 对象中。

java

/** * 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

java

@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

java

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

java

/** * 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。

java

/** * 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

java

/** * 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(); List<WrapperMappingInfo> 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 Map

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