tomcat整体架构
Server：代表整个服务，也能够了解为tomcat。
service:代表一个服务，它将若干个connector和contain连接起来。
connector：连接器，解决用户的web申请，反对三种协定：
AJP
HTTP
HTTPS
Container：容器，能够看做servelet容器。
engine：servelet引擎，一个container只能有一个engine，engine也能够看做是container自身。
host：虚拟主机，比方www.baidu.com，localhost，一个engine能够有多个host。
context：代表一个利用，比方订单服务order，url就为localhost/order,用户服务user，url就为localhost/user。一个host能够有多个context
Wrapper：servelet，比方订单信息，url就为localhost/order/detail/1，一个context能够有多个wrapper。
从配置文件server.xml更能感触分层构造：
tomcat初始化流程
启动流程：
BootStrap.main->
BootStrap.load->Catalina.load->Server.init->Service.init->engine.init->connector.init->
BootStrap.start->Server.start->service-start->engine.start->host.start（被engine异步启动）->context.start(被host异步启动)->connector.start
能够看到，次要分两步BootStrap的load和start办法，这两个办法里都是逐级调用下一级的init或start办法。
从咱们启动tomcat的命令：./start.sh 动手：
#!/bin/sh# Licensed to the Apache Software Foundation (ASF) under one or more# contributor license agreements. See the NOTICE file distributed with# this work for additional information regarding copyright ownership.# The ASF licenses this file to You under the Apache License, Version 2.0# (the "License"); you may not use this file except in compliance with# the License. You may obtain a copy of the License at## http://www.apache.org/licenses/LICENSE-2.0## Unless required by applicable law or agreed to in writing, software# distributed under the License is distributed on an "AS IS" BASIS,# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.# See the License for the specific language governing permissions and# limitations under the License.# -----------------------------------------------------------------------------# Start Script for the CATALINA Server# -----------------------------------------------------------------------------# Better OS/400 detection: see Bugzilla 31132os400=falsecase "`uname`" inOS400*) os400=true;;esac# resolve links - $0 may be a softlinkPRG="$0"while [ -h "$PRG" ] ; do ls=`ls -ld "$PRG"` link=`expr "$ls" : '.*-> \(.*\)$'` if expr "$link" : '/.*' > /dev/null; then PRG="$link" else PRG=`dirname "$PRG"`/"$link" fidonePRGDIR=`dirname "$PRG"`#通过catalina.sh来执行EXECUTABLE=catalina.sh# Check that target executable existsif $os400; then # -x will Only work on the os400 if the files are: # 1. owned by the user # 2. owned by the PRIMARY group of the user # this will not work if the user belongs in secondary groups evalelse if [ ! -x "$PRGDIR"/"$EXECUTABLE" ]; then echo "Cannot find $PRGDIR/$EXECUTABLE" echo "The file is absent or does not have execute permission" echo "This file is needed to run this program" exit 1 fifiexec "$PRGDIR"/"$EXECUTABLE" start "[email protected]"看看catalina.sh文件，代码太长，咱们间接看启动局部：
if [ "$1" = "-security" ] ; then if [ $have_tty -eq 1 ]; then echo "Using Security Manager" fi shift eval $_NOHUP "\"$_RUNJAVA\"" "\"$CATALINA_LOGGING_CONFIG\"" $LOGGING_MANAGER "$JAVA_OPTS" "$CATALINA_OPTS" \ -D$ENDORSED_PROP="\"$JAVA_ENDORSED_DIRS\"" \ -classpath "\"$CLASSPATH\"" \ -Djava.security.manager \ -Djava.security.policy=="\"$CATALINA_BASE/conf/catalina.policy\"" \ -Dcatalina.base="\"$CATALINA_BASE\"" \ -Dcatalina.home="\"$CATALINA_HOME\"" \ -Djava.io.tmpdir="\"$CATALINA_TMPDIR\"" \ # 启动Bootstrap类，并将start作为参数传进去 org.apache.catalina.startup.Bootstrap "[email protected]" start \ >> "$CATALINA_OUT" 2>&1 "&"当初进入java代码，BootStrap类：
public static void main(String args[]) { synchronized (daemonLock) { if (daemon == null) { // Don't set daemon until init() has completed Bootstrap bootstrap = new Bootstrap(); try { //初始化Bootstrap bootstrap.init(); } catch (Throwable t) { handleThrowable(t); t.printStackTrace(); return; } // 初始化实现后再赋值给daemon daemon = bootstrap; } else { // When running as a service the call to stop will be on a new // thread so make sure the correct class loader is used to // prevent a range of class not found exceptions. Thread.currentThread().setContextClassLoader(daemon.catalinaLoader); } } try { String command = "start"; if (args.length > 0) { command = args[args.length - 1]; } if (command.equals("startd")) { args[args.length - 1] = "start"; daemon.load(args); daemon.start(); } else if (command.equals("stopd")) { args[args.length - 1] = "stop"; daemon.stop(); } // 启动时走这里 else if (command.equals("start")) { daemon.setAwait(true); // load并且start daemon.load(args); daemon.start(); if (null == daemon.getServer()) { System.exit(1); } } else if (command.equals("stop")) { daemon.stopServer(args); } else if (command.equals("configtest")) { daemon.load(args); if (null == daemon.getServer()) { System.exit(1); } System.exit(0); } else { log.warn("Bootstrap: command \"" + command + "\" does not exist."); } } catch (Throwable t) { // Unwrap the Exception for clearer error reporting if (t instanceof InvocationTargetException && t.getCause() != null) { t = t.getCause(); } handleThrowable(t); t.printStackTrace(); System.exit(1); } }首先初始化Bootstrap类，而后依据传入的参数执行不同操作，启动就是执行load和start办法，先看init办法做了什么：
public void init() throws Exception { //初始化类加载器 initClassLoaders(); Thread.currentThread().setContextClassLoader(catalinaLoader); SecurityClassLoad.securityClassLoad(catalinaLoader); // Load our startup class and call its process() method if (log.isDebugEnabled()) { log.debug("Loading startup class"); } Class<?> startupClass = catalinaLoader.loadClass("org.apache.catalina.startup.Catalina"); Object startupInstance = startupClass.getConstructor().newInstance(); // Set the shared extensions class loader if (log.isDebugEnabled()) { log.debug("Setting startup class properties"); } String methodName = "setParentClassLoader"; Class<?> paramTypes[] = new Class[1]; // 指定 paramTypes[0] = Class.forName("java.lang.ClassLoader"); Object paramValues[] = new Object[1]; paramValues[0] = sharedLoader; Method method = startupInstance.getClass().getMethod(methodName, paramTypes); // Catalina的父类加载器设为sharedLoader method.invoke(startupInstance, paramValues); catalinaDaemon = startupInstance; //Catalina实例 }initClassLoaders（）：
private void initClassLoaders() { try { // 初始化common类加载器 commonLoader = createClassLoader("common", null); if (commonLoader == null) { // no config file, default to this loader - we might be in a 'single' env. commonLoader = this.getClass().getClassLoader(); } // 父类加载器为commonLoader catalinaLoader = createClassLoader("server", commonLoader); sharedLoader = createClassLoader("shared", commonLoader); } catch (Throwable t) { handleThrowable(t); log.error("Class loader creation threw exception", t); System.exit(1); } } private ClassLoader createClassLoader(String name, ClassLoader parent) throws Exception { // catalinaLoader和sharedLoader的加门路为空，所以应用父类加载器 String value = CatalinaProperties.getProperty(name + ".loader"); if ((value == null) || (value.equals(""))) { return parent; } value = replace(value); List<Repository> repositories = new ArrayList<>(); String[] repositoryPaths = getPaths(value); for (String repository : repositoryPaths) { // Check for a JAR URL repository try { @SuppressWarnings("unused") URL url = new URL(repository); repositories.add(new Repository(repository, RepositoryType.URL)); continue; } catch (MalformedURLException e) { // Ignore } // 遍历指定目录下的jar包 // Local repository if (repository.endsWith("*.jar")) { repository = repository.substring (0, repository.length() - "*.jar".length()); repositories.add(new Repository(repository, RepositoryType.GLOB)); } else if (repository.endsWith(".jar")) { repositories.add(new Repository(repository, RepositoryType.JAR)); } else { repositories.add(new Repository(repository, RepositoryType.DIR)); } } return ClassLoaderFactory.createClassLoader(repositories, parent); }initClassLoaders办法初始化了三个类加载器：commonLoader，catalinaLoader，sharedLoader，并将catalinaLoader，sharedLoader的父类加载器指定为commonLoader，初始化类加载器后又实例化了catalina实例，init办法完结，再看load办法：
/** * Load daemon. */ private void load(String[] arguments) throws Exception { // Call the load() method String methodName = "load"; Object param[]; Class<?> paramTypes[]; if (arguments==null || arguments.length==0) { paramTypes = null; param = null; } else { paramTypes = new Class[1]; paramTypes[0] = arguments.getClass(); param = new Object[1]; param[0] = arguments; } Method method = catalinaDaemon.getClass().getMethod(methodName, paramTypes); if (log.isDebugEnabled()) { log.debug("Calling startup class " + method); } // 调用了catalina的load办法 method.invoke(catalinaDaemon, param); }其实就是调用了Catalina的load办法:
public void load() { if (loaded) { return; } loaded = true; long t1 = System.nanoTime(); initDirs(); // Before digester - it may be needed initNaming(); // Create and execute our Digester //xml文件解析器，比方解析server.xml Digester digester = createStartDigester(); InputSource inputSource = null; InputStream inputStream = null; File file = null; try { try { file = configFile(); inputStream = new FileInputStream(file); inputSource = new InputSource(file.toURI().toURL().toString()); } catch (Exception e) { if (log.isDebugEnabled()) { log.debug(sm.getString("catalina.configFail", file), e); } } if (inputStream == null) { try { inputStream = getClass().getClassLoader() .getResourceAsStream(getConfigFile()); inputSource = new InputSource (getClass().getClassLoader() .getResource(getConfigFile()).toString()); } catch (Exception e) { if (log.isDebugEnabled()) { log.debug(sm.getString("catalina.configFail", getConfigFile()), e); } } } // This should be included in catalina.jar // Alternative: don't bother with xml, just create it manually. if (inputStream == null) { try { inputStream = getClass().getClassLoader() .getResourceAsStream("server-embed.xml"); inputSource = new InputSource (getClass().getClassLoader() .getResource("server-embed.xml").toString()); } catch (Exception e) { if (log.isDebugEnabled()) { log.debug(sm.getString("catalina.configFail", "server-embed.xml"), e); } } } if (inputStream == null || inputSource == null) { if (file == null) { log.warn(sm.getString("catalina.configFail", getConfigFile() + "] or [server-embed.xml]")); } else { log.warn(sm.getString("catalina.configFail", file.getAbsolutePath())); if (file.exists() && !file.canRead()) { log.warn("Permissions incorrect, read permission is not allowed on the file."); } } return; } try { inputSource.setByteStream(inputStream); digester.push(this); digester.parse(inputSource); } catch (SAXParseException spe) { log.warn("Catalina.start using " + getConfigFile() + ": " + spe.getMessage()); return; } catch (Exception e) { log.warn("Catalina.start using " + getConfigFile() + ": " , e); return; } } finally { if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { // Ignore } } } getServer().setCatalina(this); getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile()); getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile()); // Stream redirection initStreams(); // Start the new server try { // 重点看init办法 getServer().init(); } catch (LifecycleException e) { if (Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE")) { throw new java.lang.Error(e); } else { log.error("Catalina.start", e); } } long t2 = System.nanoTime(); if(log.isInfoEnabled()) { log.info("Initialization processed in " + ((t2 - t1) / 1000000) + " ms"); } }getServer().init()会调用LifeCycleBase的init办法，LifeCycle是一个治理tomcat生命周期的接口，LifeCycleBase是它的实现类：
@Override public final synchronized void init() throws LifecycleException { if (!state.equals(LifecycleState.NEW)) { invalidTransition(Lifecycle.BEFORE_INIT_EVENT); } try { setStateInternal(LifecycleState.INITIALIZING, null, false); // 进入这里 initInternal(); setStateInternal(LifecycleState.INITIALIZED, null, false); } catch (Throwable t) { handleSubClassException(t, "lifecycleBase.initFail", toString()); } }initInternal()是个形象办法，由StandServer实现：
@Override protected void initInternal() throws LifecycleException { super.initInternal(); // Register global String cache // Note although the cache is global, if there are multiple Servers // present in the JVM (may happen when embedding) then the same cache // will be registered under multiple names onameStringCache = register(new StringCache(), "type=StringCache"); // Register the MBeanFactory MBeanFactory factory = new MBeanFactory(); factory.setContainer(this); onameMBeanFactory = register(factory, "type=MBeanFactory"); // Register the naming resources globalNamingResources.init(); // Populate the extension validator with JARs from common and shared // class loaders if (getCatalina() != null) { ClassLoader cl = getCatalina().getParentClassLoader(); // Walk the class loader hierarchy. Stop at the system class loader. // This will add the shared (if present) and common class loaders while (cl != null && cl != ClassLoader.getSystemClassLoader()) { if (cl instanceof URLClassLoader) { URL[] urls = ((URLClassLoader) cl).getURLs(); for (URL url : urls) { if (url.getProtocol().equals("file")) { try { File f = new File (url.toURI()); if (f.isFile() && f.getName().endsWith(".jar")) { ExtensionValidator.addSystemResource(f); } } catch (URISyntaxException | IOException e) { // Ignore } } } } cl = cl.getParent(); } } // Initialize our defined Services for (Service service : services) { // 进入这里 service.init(); } }service是StandService，但它的init是父类 LifeCycleBase的办法，又一次运行了这个办法：
@Override public final synchronized void init() throws LifecycleException { if (!state.equals(LifecycleState.NEW)) { invalidTransition(Lifecycle.BEFORE_INIT_EVENT); } try { setStateInternal(LifecycleState.INITIALIZING, null, false); // 进入这里，这里由StandService实现 initInternal(); setStateInternal(LifecycleState.INITIALIZED, null, false); } catch (Throwable t) { handleSubClassException(t, "lifecycleBase.initFail", toString()); } } @Override protected void initInternal() throws LifecycleException { super.initInternal(); if (engine != null) { //初始化engine engine.init(); } // Initialize any Executors for (Executor executor : findExecutors()) { if (executor instanceof JmxEnabled) { ((JmxEnabled) executor).setDomain(getDomain()); } //初始化executor executor.init(); } // Initialize mapper listener //初始化mapperListener mapperListener.init(); // Initialize our defined Connectors synchronized (connectorsLock) { for (Connector connector : connectors) { try { //初始化connector connector.init(); } catch (Exception e) { String message = sm.getString( "standardService.connector.initFailed", connector); log.error(message, e); if (Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE")) { throw new LifecycleException(message); } } } } }又一次调用了LifeCycleBase的init办法：
@Override public final synchronized void init() throws LifecycleException { if (!state.equals(LifecycleState.NEW)) { invalidTransition(Lifecycle.BEFORE_INIT_EVENT); } try { setStateInternal(LifecycleState.INITIALIZING, null, false); // 进入这里，这次由Connect实现 initInternal(); setStateInternal(LifecycleState.INITIALIZED, null, false); } catch (Throwable t) { handleSubClassException(t, "lifecycleBase.initFail", toString()); } } @Override protected void initInternal() throws LifecycleException { super.initInternal(); // Initialize adapter adapter = new CoyoteAdapter(this); protocolHandler.setAdapter(adapter); // Make sure parseBodyMethodsSet has a default if (null == parseBodyMethodsSet) { setParseBodyMethods(getParseBodyMethods()); } if (protocolHandler.isAprRequired() && !AprLifecycleListener.isInstanceCreated()) { throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprListener", getProtocolHandlerClassName())); } if (protocolHandler.isAprRequired() && !AprLifecycleListener.isAprAvailable()) { throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprLibrary", getProtocolHandlerClassName())); } if (AprLifecycleListener.isAprAvailable() && AprLifecycleListener.getUseOpenSSL() && protocolHandler instanceof AbstractHttp11JsseProtocol) { AbstractHttp11JsseProtocol<?> jsseProtocolHandler = (AbstractHttp11JsseProtocol<?>) protocolHandler; if (jsseProtocolHandler.isSSLEnabled() && jsseProtocolHandler.getSslImplementationName() == null) { // OpenSSL is compatible with the JSSE configuration, so use it if APR is available jsseProtocolHandler.setSslImplementationName(OpenSSLImplementation.class.getName()); } } try { // 初始化ProtocolHandler protocolHandler.init(); } catch (Exception e) { throw new LifecycleException( sm.getString("coyoteConnector.protocolHandlerInitializationFailed"), e); } }protocolHandler.init()由AbstractProtocol实现：
@Override public void init() throws Exception { if (getLog().isInfoEnabled()) { getLog().info(sm.getString("abstractProtocolHandler.init", getName())); logPortOffset(); } if (oname == null) { // Component not pre-registered so register it oname = createObjectName(); if (oname != null) { Registry.getRegistry(null, null).registerComponent(this, oname, null); } } if (this.domain != null) { ObjectName rgOname = new ObjectName(domain + ":type=GlobalRequestProcessor,name=" + getName()); this.rgOname = rgOname; Registry.getRegistry(null, null).registerComponent( getHandler().getGlobal(), rgOname, null); } String endpointName = getName(); endpoint.setName(endpointName.substring(1, endpointName.length()-1)); endpoint.setDomain(domain); // 初始化endPoint endpoint.init(); }endpoint.init()由AbstractEndPoint实现：
public void init() throws Exception { if (bindOnInit) { // 重点在这里 bindWithCleanup(); bindState = BindState.BOUND_ON_INIT; } if (this.domain != null) { // Register endpoint (as ThreadPool - historical name) oname = new ObjectName(domain + ":type=ThreadPool,name=\"" + getName() + "\""); Registry.getRegistry(null, null).registerComponent(this, oname, null); ObjectName socketPropertiesOname = new ObjectName(domain + ":type=SocketProperties,name=\"" + getName() + "\""); socketProperties.setObjectName(socketPropertiesOname); Registry.getRegistry(null, null).registerComponent(socketProperties, socketPropertiesOname, null); for (SSLHostConfig sslHostConfig : findSslHostConfigs()) { registerJmx(sslHostConfig); } } } private void bindWithCleanup() throws Exception { try { bind(); } catch (Throwable t) { // Ensure open sockets etc. are cleaned up if something goes // wrong during bind ExceptionUtils.handleThrowable(t); unbind(); throw t; } }进入NioEndPoint：
/** * Initialize the endpoint. */ @Override public void bind() throws Exception { // 初始化ServerSocket initServerSocket(); setStopLatch(new CountDownLatch(1)); // Initialize SSL if needed initialiseSsl(); } // Separated out to make it easier for folks that extend NioEndpoint to // implement custom [server]sockets protected void initServerSocket() throws Exception { if (getUseInheritedChannel()) { // Retrieve the channel provided by the OS Channel ic = System.inheritedChannel(); if (ic instanceof ServerSocketChannel) { serverSock = (ServerSocketChannel) ic; } if (serverSock == null) { throw new IllegalArgumentException(sm.getString("endpoint.init.bind.inherited")); } } else { serverSock = ServerSocketChannel.open(); socketProperties.setProperties(serverSock.socket()); InetSocketAddress addr = new InetSocketAddress(getAddress(), getPortWithOffset()); serverSock.socket().bind(addr,getAcceptCount()); } serverSock.configureBlocking(true); //mimic APR behavior }BootStrap的load办法实现，就是初始化了一些组件。
再来看start办法：
/** * Start the Catalina daemon. * @throws Exception Fatal start error */ public void start() throws Exception { if (catalinaDaemon == null) { init(); } Method method = catalinaDaemon.getClass().getMethod("start", (Class [])null); // 调用Catalina的start办法 method.invoke(catalinaDaemon, (Object [])null); } /** * Start a new server instance. */ public void start() { if (getServer() == null) { load(); } if (getServer() == null) { log.fatal("Cannot start server. Server instance is not configured."); return; } long t1 = System.nanoTime(); // Start the new server try { // start getServer().start(); } catch (LifecycleException e) { log.fatal(sm.getString("catalina.serverStartFail"), e); try { getServer().destroy(); } catch (LifecycleException e1) { log.debug("destroy() failed for failed Server ", e1); } return; } long t2 = System.nanoTime(); if(log.isInfoEnabled()) { log.info("Server startup in " + ((t2 - t1) / 1000000) + " ms"); } // Register shutdown hook if (useShutdownHook) { if (shutdownHook == null) { shutdownHook = new CatalinaShutdownHook(); } Runtime.getRuntime().addShutdownHook(shutdownHook); // If JULI is being used, disable JULI's shutdown hook since // shutdown hooks run in parallel and log messages may be lost // if JULI's hook completes before the CatalinaShutdownHook() LogManager logManager = LogManager.getLogManager(); if (logManager instanceof ClassLoaderLogManager) { ((ClassLoaderLogManager) logManager).setUseShutdownHook( false); } } if (await) { await(); stop(); } }getServer().start()调用LifecycleBase的start办法：
/** * {@inheritDoc} */ @Override public final synchronized void start() throws LifecycleException { 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; } // start办法时，state为INITIALIZED if (state.equals(LifecycleState.NEW)) { init(); } else if (state.equals(LifecycleState.FAILED)) { stop(); } else if (!state.equals(LifecycleState.INITIALIZED) && !state.equals(LifecycleState.STOPPED)) { invalidTransition(Lifecycle.BEFORE_START_EVENT); } try { setStateInternal(LifecycleState.STARTING_PREP, null, false); //进入这里，调用的是StandServer的startInternal（） 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)) { // 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 { 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. handleSubClassException(t, "lifecycleBase.startFail", toString()); } } @Override protected void startInternal() throws LifecycleException { fireLifecycleEvent(CONFIGURE_START_EVENT, null); setState(LifecycleState.STARTING); globalNamingResources.start(); // Start our defined Services synchronized (servicesLock) { for (Service service : services) { // standService service.start(); } } }前面和load办法一样，都是调用了父类LifecycleBase的模板办法实现各个组件的start。