今天小编给大家分享一下ServletWebServerApplicationContext如何创建Web容器Tomcat的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。
ServletWebServerApplicationContext实现了父类AbstractApplicationContext的onRefresh模板方法，在这里进行了拓展创建了Web容器。
@Override
protected void onRefresh() {
super.onRefresh();
try {
createWebServer();
}
catch (Throwable ex) {
throw new ApplicationContextException("Unable to start web server", ex);
}
}private void createWebServer() {
WebServer webServer = this.webServer;
ServletContext servletContext = getServletContext();
if (webServer == null && servletContext == null) {
//一、获取Web服务器工厂
ServletWebServerFactory factory = getWebServerFactory();
//二、获取Web服务
this.webServer = factory.getWebServer(getSelfInitializer());
//三、注册Bean生命周期（在容器启动和销毁时调用）
getBeanFactory().registerSingleton("webServerGracefulShutdown",
new WebServerGracefulShutdownLifecycle(this.webServer));
getBeanFactory().registerSingleton("webServerStartStop",
new WebServerStartStopLifecycle(this, this.webServer));
}
else if (servletContext != null) {
try {
getSelfInitializer().onStartup(servletContext);
}
catch (ServletException ex) {
throw new ApplicationContextException("Cannot initialize servlet context", ex);
}
}
//四、初始化上下文环境
initPropertySources();
}protected ServletWebServerFactory getWebServerFactory() {
// Use bean names so that we don't consider the hierarchy
//获取Web服务器工厂名称
String[] beanNames = getBeanFactory().getBeanNamesForType(ServletWebServerFactory.class);
if (beanNames.length == 0) {
throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to missing "
+ "ServletWebServerFactory bean.");
}
if (beanNames.length > 1) {
throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to multiple "
+ "ServletWebServerFactory beans : " + StringUtils.arrayToCommaDelimitedString(beanNames));
}
//从容器中获取Web服务器工厂实例
return getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class);
}这里的Web服务器工厂是通过ServletWebServerFactoryAutoConfiguration自动配置类导入进来的。
@Configuration(proxyBeanMethods = false)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@ConditionalOnClass(ServletRequest.class)
//Web启动环境
@ConditionalOnWebApplication(type = Type.SERVLET)
@EnableConfigurationProperties(ServerProperties.class)
//2.1导入Web工厂
@Import({ ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class,
ServletWebServerFactoryConfiguration.EmbeddedTomcat.class,
ServletWebServerFactoryConfiguration.EmbeddedJetty.class,
ServletWebServerFactoryConfiguration.EmbeddedUndertow.class })
public class ServletWebServerFactoryAutoConfiguration {
//导入Web服务器工厂自定义程序
@Bean
public ServletWebServerFactoryCustomizer servletWebServerFactoryCustomizer(ServerProperties serverProperties) {
return new ServletWebServerFactoryCustomizer(serverProperties);
}
//如果是Tomcat则导入Tomcat自定义程序
@Bean
@ConditionalOnClass(name = "org.apache.catalina.startup.Tomcat")
public TomcatServletWebServerFactoryCustomizer tomcatServletWebServerFactoryCustomizer(
ServerProperties serverProperties) {
return new TomcatServletWebServerFactoryCustomizer(serverProperties);
}
@Bean
@ConditionalOnMissingFilterBean(ForwardedHeaderFilter.class)
@ConditionalOnProperty(value = "server.forward-headers-strategy", havingValue = "framework")
public FilterRegistrationBean<ForwardedHeaderFilter> forwardedHeaderFilter() {
ForwardedHeaderFilter filter = new ForwardedHeaderFilter();
FilterRegistrationBean<ForwardedHeaderFilter> registration = new FilterRegistrationBean<>(filter);
registration.setDispatcherTypes(DispatcherType.REQUEST, DispatcherType.ASYNC, DispatcherType.ERROR);
registration.setOrder(Ordered.HIGHEST_PRECEDENCE);
return registration;
}
/**
* Registers a {@link WebServerFactoryCustomizerBeanPostProcessor}. Registered via
* {@link ImportBeanDefinitionRegistrar} for early registration.
*/
public static class BeanPostProcessorsRegistrar implements ImportBeanDefinitionRegistrar, BeanFactoryAware {
private ConfigurableListableBeanFactory beanFactory;
@Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
if (beanFactory instanceof ConfigurableListableBeanFactory) {
this.beanFactory = (ConfigurableListableBeanFactory) beanFactory;
}
}
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata,
BeanDefinitionRegistry registry) {
if (this.beanFactory == null) {
return;
}
registerSyntheticBeanIfMissing(registry, "webServerFactoryCustomizerBeanPostProcessor",
WebServerFactoryCustomizerBeanPostProcessor.class);
registerSyntheticBeanIfMissing(registry, "errorPageRegistrarBeanPostProcessor",
ErrorPageRegistrarBeanPostProcessor.class);
}
private void registerSyntheticBeanIfMissing(BeanDefinitionRegistry registry, String name, Class<?> beanClass) {
if (ObjectUtils.isEmpty(this.beanFactory.getBeanNamesForType(beanClass, true, false))) {
RootBeanDefinition beanDefinition = new RootBeanDefinition(beanClass);
beanDefinition.setSynthetic(true);
registry.registerBeanDefinition(name, beanDefinition);
}
}
}
}@Configuration
class ServletWebServerFactoryConfiguration {
ServletWebServerFactoryConfiguration() {
}
//1.如果容器中有Servlet，Undertow，SslClientAuthMode就会创建Undertow工厂
@Configuration
@ConditionalOnClass({Servlet.class, Undertow.class, SslClientAuthMode.class})
@ConditionalOnMissingBean(
value = {ServletWebServerFactory.class},
search = SearchStrategy.CURRENT
)
public static class EmbeddedUndertow {
public EmbeddedUndertow() {
}
@Bean
public UndertowServletWebServerFactory undertowServletWebServerFactory() {
return new UndertowServletWebServerFactory();
}
}
//2.如果容器中有Servlet，Server，Loader就会创建Jetty工厂
@Configuration
@ConditionalOnClass({Servlet.class, Server.class, Loader.class, WebAppContext.class})
@ConditionalOnMissingBean(
value = {ServletWebServerFactory.class},
search = SearchStrategy.CURRENT
)
public static class EmbeddedJetty {
public EmbeddedJetty() {
}
@Bean
public JettyServletWebServerFactory JettyServletWebServerFactory() {
return new JettyServletWebServerFactory();
}
}
//3.如果容器中有Servlet，Tomcat，UpgradeProtocol就会创建Tomcat工厂
@Configuration
@ConditionalOnClass({Servlet.class, Tomcat.class, UpgradeProtocol.class})
@ConditionalOnMissingBean(
value = {ServletWebServerFactory.class},
search = SearchStrategy.CURRENT
)
public static class EmbeddedTomcat {
public EmbeddedTomcat() {
}
@Bean
public TomcatServletWebServerFactory tomcatServletWebServerFactory() {
return new TomcatServletWebServerFactory();
}
}
}public static final String DEFAULT_PROTOCOL = "org.apache.coyote.http11.Http11NioProtocol";
private String protocol = DEFAULT_PROTOCOL;
public WebServer getWebServer(ServletContextInitializer... initializers) {
Tomcat tomcat = new Tomcat();
// 给嵌入式Tomcat创建一个临时文件夹，用于存放Tomcat运行中需要的文件
File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");
tomcat.setBaseDir(baseDir.getAbsolutePath());
// Tomcat核心概念：Connector，默认放入的protocol为NIO模式
Connector connector = new Connector(this.protocol);
// 给Service添加Connector
tomcat.getService().addConnector(connector);
// 执行定制器，修改即将设置到Tomcat中的Connector
customizeConnector(connector);
tomcat.setConnector(connector);
// 关闭热部署（嵌入式Tomcat不存在修改web.xml、war包等情况）
tomcat.getHost().setAutoDeploy(false);
// 设置backgroundProcessorDelay机制
configureEngine(tomcat.getEngine());
for (Connector additionalConnector : this.additionalTomcatConnectors) {
tomcat.getService().addConnector(additionalConnector);
}
// 2.1 创建TomcatEmbeddedContext
prepareContext(tomcat.getHost(), initializers);
// 2.2. 创建TomcatWebServer
return getTomcatWebServer(tomcat);
}（注释均已在源码中标注好，小伙伴们对哪一步感兴趣可以借助IDE自己动手Debug体会一下实现）
protected void prepareContext(Host host, ServletContextInitializer[] initializers) {
File documentRoot = getValidDocumentRoot();
// 创建TomcatEmbeddedContext
TomcatEmbeddedContext context = new TomcatEmbeddedContext();
if (documentRoot != null) {
context.setResources(new LoaderHidingResourceRoot(context));
}
context.setName(getContextPath());
context.setDisplayName(getDisplayName());
// 设置contextPath，很熟悉了
context.setPath(getContextPath());
// 给嵌入式Tomcat创建docbase的临时文件夹
File docBase = (documentRoot != null) ? documentRoot : createTempDir("tomcat-docbase");
context.setDocBase(docBase.getAbsolutePath());
// 注册监听器
context.addLifecycleListener(new FixContextListener());
context.setParentClassLoader((this.resourceLoader != null) ? this.resourceLoader.getClassLoader()
: ClassUtils.getDefaultClassLoader());
// 设置默认编码映射
resetDefaultLocaleMapping(context);
addLocaleMappings(context);
context.setUseRelativeRedirects(false);
try {
context.setCreateUploadTargets(true);
}
catch (NoSuchMethodError ex) {
// Tomcat is < 8.5.39. Continue.
}
configureTldSkipPatterns(context);
// 自定义的类加载器，可以加载web应用的jar包
WebappLoader loader = new WebappLoader(context.getParentClassLoader());
loader.setLoaderClass(TomcatEmbeddedWebappClassLoader.class.getName());
// 指定类加载器遵循双亲委派机制
loader.setDelegate(true);
context.setLoader(loader);
// 注册默认的Servlet
if (isRegisterDefaultServlet()) {
addDefaultServlet(context);
}
// 如果需要jsp支持，注册jsp的Servlet和Initializer
if (shouldRegisterJspServlet()) {
addJspServlet(context);
addJasperInitializer(context);
}
// 注册监听器
context.addLifecycleListener(new StaticResourceConfigurer(context));
ServletContextInitializer[] initializersToUse = mergeInitializers(initializers);
host.addChild(context);
configureContext(context, initializersToUse);
postProcessContext(context);
}protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {
return new TomcatWebServer(tomcat, getPort() >= 0, getShutdown());
}进入TomcatWebServer构造方法中：
public TomcatWebServer(Tomcat tomcat, boolean autoStart) {
Assert.notNull(tomcat, "Tomcat Server must not be null");
this.tomcat = tomcat;
this.autoStart = autoStart;
//初始化服务
initialize();
}初始化TomcatWebServer
private void initialize() throws WebServerException {
logger.info("Tomcat initialized with port(s): " + getPortsDescription(false));
synchronized (this.monitor) {
try {
//设置Engine的id
addInstanceIdToEngineName();
//获取Context（TomcatEmbeddedContext 2.1中创建出来的）
Context context = findContext();
//添加监听器 TomcatEmbeddedContext
//在服务启动时如果有连接进来先删除连接，以便在启动服务时不会发生协议绑定。
context.addLifecycleListener((event) -> {
if (context.equals(event.getSource()) && Lifecycle.START_EVENT.equals(event.getType())) {
// Remove service connectors so that protocol binding doesn't
// happen when the service is started.
//删除ServiceConnectors，以便在启动服务时不会发生协议绑定。
removeServiceConnectors();
}
});
// Start the server to trigger initialization listeners
//2.2.1 启动Tomcat
this.tomcat.start();
// We can re-throw failure exception directly in the main thread
//Tomcat启动有异常需要在主线程中抛出
rethrowDeferredStartupExceptions();
try {
ContextBindings.bindClassLoader(context, context.getNamingToken(), getClass().getClassLoader());
}
catch (NamingException ex) {
// Naming is not enabled. Continue
}
// Unlike Jetty, all Tomcat threads are daemon threads. We create a
// blocking non-daemon to stop immediate shutdown
//开启阻塞非守护线程停止web容器
startDaemonAwaitThread();
}
catch (Exception ex) {
stopSilently();
destroySilently();
throw new WebServerException("Unable to start embedded Tomcat", ex);
}
}
}创建和初始化Server和Service
public void start() throws LifecycleException {
//创建服务（Server和Service）
getServer();
server.start();
}启动服务
public final synchronized void start() throws LifecycleException {
//如果是正在启动或启动状态
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;
}
//如果是新建状态
if (state.equals(LifecycleState.NEW)) {
//2.2.1.1 初始化服务
init();
//如果是失败状态
} else if (state.equals(LifecycleState.FAILED)) {
//停止服务
stop();
//如果不是初始化也不是停止状态
} else if (!state.equals(LifecycleState.INITIALIZED) &&
!state.equals(LifecycleState.STOPPED)) {
//修改状态
invalidTransition(Lifecycle.BEFORE_START_EVENT);
}
try {
//修改状态为准备启动
setStateInternal(LifecycleState.STARTING_PREP, null, false);
//2.2.1.2 启动Internal
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());
}
}2.2.1.1 初始化Server
public final synchronized void init() throws LifecycleException {
if (!state.equals(LifecycleState.NEW)) {
invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
}
try {
//设置状态为初始化
setStateInternal(LifecycleState.INITIALIZING, null, false);
//初始化
initInternal();
//设置状态为初始化完成
setStateInternal(LifecycleState.INITIALIZED, null, false);
} catch (Throwable t) {
handleSubClassException(t, "lifecycleBase.initFail", toString());
}
}初始化 Server
protected void initInternal() throws LifecycleException {
//调用父类初始化（设置名称：Tomcat，类型：Server）
super.initInternal();
// Initialize utility executor
reconfigureUtilityExecutor(getUtilityThreadsInternal(utilityThreads));
//注册线程池
register(utilityExecutor, "type=UtilityExecutor");
// 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
//注册字符串缓存
onameStringCache = register(new StringCache(), "type=StringCache");
// Register the MBeanFactory
MBeanFactory factory = new MBeanFactory();
factory.setContainer(this);
//注册Bean工厂
onameMBeanFactory = register(factory, "type=MBeanFactory");
// Register the naming resources
//注册命名资源
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 e) {
// Ignore
} catch (IOException e) {
// Ignore
}
}
}
}
cl = cl.getParent();
}
}
// Initialize our defined Services
//2.2.1.1.1 初始化service（2.2.1最开始时创建）
for (Service service : services) {
service.init();
}
}初始化Service
public final synchronized void init() throws LifecycleException {
if (!state.equals(LifecycleState.NEW)) {
invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
}
try {
//设置状态为初始化
setStateInternal(LifecycleState.INITIALIZING, null, false);
//初始化
initInternal();
//设置状态为初始化完成
setStateInternal(LifecycleState.INITIALIZED, null, false);
} catch (Throwable t) {
handleSubClassException(t, "lifecycleBase.initFail", toString());
}
}初始化Service
protected void initInternal() throws LifecycleException {
//调用父类初始化（设置名称：Tomcat，类型：Server）
super.initInternal();
//2.2.1.1.1.1 初始化engine
if (engine != null) {
engine.init();
}
// Initialize any Executors
//2.2.1.1.1.2 初始化executor
for (Executor executor : findExecutors()) {
if (executor instanceof JmxEnabled) {
((JmxEnabled) executor).setDomain(getDomain());
}
executor.init();
}
// Initialize mapper listener
//2.2.1.1.1.3 初始化mapperListener
mapperListener.init();
// Initialize our defined Connectors
//2.2.1.1.1.4 初始化connector
synchronized (connectorsLock) {
for (Connector connector : connectors) {
connector.init();
}
}
}初始化engine
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.
// 在尝试启动一个Realm之前，请确保存在一个Realm。如有必要，这将创建默认的NullRealm
getRealm();
super.initInternal();
}
public Realm getRealm() {
Realm configured = super.getRealm();
// If no set realm has been called - default to NullRealm
// This can be overridden at engine, context and host level
if (configured == null) {
configured = new NullRealm();
this.setRealm(configured);
}
return configured;
}初始化executor
它还是调的父类 LifecycleMBeanBase 的方法
protected void initInternal() throws LifecycleException {
super.initInternal();
}初始化mapperListener
protected void initInternal() throws LifecycleException {
// If oname is not null then registration has already happened via preRegister().
// 如果oname不为null，则已经通过preRegister()进行了注册
if (oname == null) {
mserver = Registry.getRegistry(null, null).getMBeanServer();
oname = register(this, getObjectNameKeyProperties());
}
}初始化connector
protected void initInternal() throws LifecycleException {
super.initInternal();
if (protocolHandler == null) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerInstantiationFailed"));
}
// Initialize adapter
adapter = new CoyoteAdapter(this);
protocolHandler.setAdapter(adapter);
if (service != null) {
protocolHandler.setUtilityExecutor(service.getServer().getUtilityExecutor());
}
// Make sure parseBodyMethodsSet has a default
if (null == parseBodyMethodsSet) {
setParseBodyMethods(getParseBodyMethods());
}
if (protocolHandler.isAprRequired() && !AprStatus.isInstanceCreated()) {
throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprListener",
getProtocolHandlerClassName()));
}
if (protocolHandler.isAprRequired() && !AprStatus.isAprAvailable()) {
throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprLibrary",
getProtocolHandlerClassName()));
}
if (AprStatus.isAprAvailable() && AprStatus.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 {
//2.2.1.1.1.5 初始化protocolHandler
protocolHandler.init();
} catch (Exception e) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerInitializationFailed"), e);
}
}初始化protocolHandler
public void init() throws Exception {
// Upgrade protocols have to be configured first since the endpoint
// init (triggered via super.init() below) uses this list to configure
// the list of ALPN protocols to advertise
// 必须先配置升级协议，因为端点初始化（通过下面的super.init()触发）使用此列表来配置要发布的ALPN协议列表
for (UpgradeProtocol upgradeProtocol : upgradeProtocols) {
configureUpgradeProtocol(upgradeProtocol);
}
super.init();
}Debug发现这个 upgradeProtocols 为空，直接走下面父类（AbstractProtocol）的 init 方法：
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) {
rgOname = new ObjectName(domain + ":type=GlobalRequestProcessor,name=" + getName());
Registry.getRegistry(null, null).registerComponent(
getHandler().getGlobal(), rgOname, null);
}
String endpointName = getName();
endpoint.setName(endpointName.substring(1, endpointName.length()-1));
endpoint.setDomain(domain);
//2.2.1.1.1.6 初始化endpoint
endpoint.init();
}上面又是一堆初始化，这个咱暂且不关注，注意最底下有一个 endpoint.init ：
初始化endpoint
来到 AbstractEndPoint ：
public final void init() throws Exception {
// Debug为false
if (bindOnInit) {
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=ThreadPool,name="" + getName() + "",subType=SocketProperties");
socketProperties.setObjectName(socketPropertiesOname);
Registry.getRegistry(null, null).registerComponent(socketProperties, socketPropertiesOname, null);
for (SSLHostConfig sslHostConfig : findSslHostConfigs()) {
registerJmx(sslHostConfig);
}
}
}这里面又是初始化 oname ，又是配置 socketProperties 的，但这里面再也没见到 init 方法，证明这部分初始化过程已经结束了。
嵌入式 Tomcat 的组件初始化步骤顺序如下：
Server
Service
Engine
Executor
MapperListener
Connector
Protocol
EndPoint
startInternal 方法中有两部分启动：globalNamingResources 启动，services 启动。分别来看：
protected void startInternal() throws LifecycleException {
// 发布启动事件
fireLifecycleEvent(CONFIGURE_START_EVENT, null);
setState(LifecycleState.STARTING);
// 2.2.1.2.1 NamingResources启动
globalNamingResources.start();
// Start our defined Services
synchronized (servicesLock) {
for (int i = 0; i < services.length; i++) {
// 2.2.1.2.2 Service启动
services[i].start();
}
}
if (periodicEventDelay > 0) {
monitorFuture = getUtilityExecutor().scheduleWithFixedDelay(
new Runnable() {
@Override
public void run() {
startPeriodicLifecycleEvent();
}
}, 0, 60, TimeUnit.SECONDS);
}
}只是发布事件和设置状态而已
protected void startInternal() throws LifecycleException {
fireLifecycleEvent(CONFIGURE_START_EVENT, null);
setState(LifecycleState.STARTING);
}依次启动 Engine 、Executor 、MapperListener 、Connector
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) {
// 2.2.1.2.2.1 启动Engine
engine.start();
}
}
synchronized (executors) {
for (Executor executor: executors) {
// 2.2.1.2.2.3 启动Executor
executor.start();
}
}
// 2.2.1.2.2.4 启动MapperListener
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) {
// 2.2.1.2.2.5 启动connector
connector.start();
}
}
}
}protected synchronized void startInternal() throws LifecycleException {
// Log our server identification information
if (log.isInfoEnabled()) {
log.info(sm.getString("standardEngine.start", ServerInfo.getServerInfo()));
}
// Standard container startup
super.startInternal();
}它直接调的父类 ContainerBase 的 startInternal 方法：
protected synchronized void startInternal() throws LifecycleException {
// Start our subordinate components, if any
logger = null;
getLogger();
// Cluster与集群相关，SpringBoot项目中使用嵌入式Tomcat，不存在集群
Cluster cluster = getClusterInternal();
if (cluster instanceof Lifecycle) {
((Lifecycle) cluster).start();
}
// Realm与授权相关
Realm realm = getRealmInternal();
if (realm instanceof Lifecycle) {
((Lifecycle) realm).start();
}
// Start our child containers, if any
// Container的类型是StandardHost
Container children[] = findChildren();
List<Future<Void>> results = new ArrayList<>();
for (int i = 0; i < children.length; i++) {
//异步初始化Host
results.add(startStopExecutor.submit(new StartChild(children[i])));
}
MultiThrowable multiThrowable = null;
for (Future<Void> result : results) {
try {
result.get();
} catch (Throwable e) {
log.error(sm.getString("containerBase.threadedStartFailed"), e);
if (multiThrowable == null) {
multiThrowable = new MultiThrowable();
}
multiThrowable.add(e);
}
}
if (multiThrowable != null) {
throw new LifecycleException(sm.getString("containerBase.threadedStartFailed"),
multiThrowable.getThrowable());
}
// Start the Valves in our pipeline (including the basic), if any
if (pipeline instanceof Lifecycle) {
((Lifecycle) pipeline).start();
}
setState(LifecycleState.STARTING);
// Start our thread
if (backgroundProcessorDelay > 0) {
monitorFuture = Container.getService(ContainerBase.this).getServer()
.getUtilityExecutor().scheduleWithFixedDelay(
new ContainerBackgroundProcessorMonitor(), 0, 60, TimeUnit.SECONDS);
}
}StartChild 实现了带返回值的异步多线程接口 Callable 核心方法就是在 call
private static class StartChild implements Callable<Void>
它实现了带返回值的异步多线程接口 Callable ！那里面的核心方法就是 call ：
public Void call() throws LifecycleException {
child.start();
return null;
}它在这里初始化 child，而通过Debug得知 child 的类型是 StandardHost，故来到 StandardHost 的 start 方法：
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) {
Valve valve =
(Valve) Class.forName(errorValve).getConstructor().newInstance();
getPipeline().addValve(valve);
}
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
log.error(sm.getString(
"standardHost.invalidErrorReportValveClass",
errorValve), t);
}
}
super.startInternal();
}上面的一个大if结构是设置错误提示页面的，下面又调父类的 startInternal ：
protected synchronized void startInternal() throws LifecycleException {
// ......
// Start our child containers, if any
Container children[] = findChildren();
List<Future<Void>> results = new ArrayList<>();
for (int i = 0; i < children.length; i++) {
results.add(startStopExecutor.submit(new StartChild(children[i])));
}又回来了。。。因为一个 Host 包含一个 Context 。
Host 搜索children就会搜到它下面的 Context ，之后又是下面的初始化过程，进入 Context 的初始化：
在TomcatEmbeddedContext有如下组件被调用了 start 方法：
StandardRoot
DirResourceSet
WebappLoader
JarResourceSet
StandardWrapper
StandardPineline
StandardWrapperValve
NonLoginAuthenticator
StandardContextValve
StandardManager
LazySessionIdGenerator
但由于 Executor 没有实现 startInternal 方法，所以不会启动
synchronized (executors) {
for (Executor executor: executors) {
executor.start();
}
}接下来启动 MapperListener ：
public void startInternal() throws LifecycleException {
setState(LifecycleState.STARTING);
Engine engine = service.getContainer();
if (engine == null) {
return;
}
// 获取当前部署的主机名（本地调试为localhost）
findDefaultHost();
// 把当前自身注册到Engine、Host、Context、Wrapper中
addListeners(engine);
// 取出的Container的类型为Host
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
//将Host、Context、Wrapper注册到当前监听器中
registerHost(host);
}
}
}最后一步是启动 Connector 。
// 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();
}
}
}启动过程依次启动了如下组件：
NamingResources
Service
Engine
Host
Context
Wrapper
Executor
MapperListener
WebServerStartStopLifecycle实现了Lifecycle，在容器刷新完成时会调用finishRefresh()
@Override
public void start() {
//启动Tomcat 容器
this.webServer.start();
this.running = true;
this.applicationContext
.publishEvent(new ServletWebServerInitializedEvent(this.webServer, this.applicationContext));
}public void start() throws WebServerException {
synchronized (this.monitor) {
if (this.started) {
return;
}
try {
// 3.1.1 还原、启动Connector
addPreviouslyRemovedConnectors();
// 只拿一个Connector
Connector connector = this.tomcat.getConnector();
if (connector != null && this.autoStart) {
// 3.1.2 延迟启动
performDeferredLoadOnStartup();
}
// 检查Connector是否正常启动
checkThatConnectorsHaveStarted();
this.started = true;
logger.info("Tomcat started on port(s): " + getPortsDescription(true) + " with context path '"
+ getContextPath() + "'");
}
// catch ......
finally {
// 解除ClassLoader与TomcatEmbeddedContext的绑定关系
Context context = findContext();
ContextBindings.unbindClassLoader(context, context.getNamingToken(), getClass().getClassLoader());
}
}
}private void addPreviouslyRemovedConnectors() {
Service[] services = this.tomcat.getServer().findServices();
for (Service service : services) {
Connector[] connectors = this.serviceConnectors.get(service);
if (connectors != null) {
for (Connector connector : connectors) {
// 添加并启动
service.addConnector(connector);
if (!this.autoStart) {
stopProtocolHandler(connector);
}
}
this.serviceConnectors.remove(service);
}
}
}可以发现它将一个缓存区的 Connector 一个一个取出放入 Service 中。注意在 service.addConnector 中有顺便启动的部分：
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()) {
// 启动Connector
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);
}前面的部分是取出 Connector ，并与 Service 绑定，之后中间部分的try块，会启动 Connector ：
protected void startInternal() throws LifecycleException {
// Validate settings before starting
if (getPortWithOffset() < 0) {
throw new LifecycleException(sm.getString(
"coyoteConnector.invalidPort", Integer.valueOf(getPortWithOffset())));
}
setState(LifecycleState.STARTING);
try {
// 启动ProtocolHandler
protocolHandler.start();
} catch (Exception e) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerStartFailed"), e);
}
}Connector 的启动会引发 ProtocolHandler 的启动：
public void start() throws Exception {
if (getLog().isInfoEnabled()) {
getLog().info(sm.getString("abstractProtocolHandler.start", getName()));
logPortOffset();
}
// 启动EndPoint
endpoint.start();
monitorFuture = getUtilityExecutor().scheduleWithFixedDelay(
new Runnable() {
@Override
public void run() {
if (!isPaused()) {
startAsyncTimeout();
}
}
}, 0, 60, TimeUnit.SECONDS);
}ProtocolHandler 的启动会引发 EndPoint 的启动，至此所有组件均已启动完毕。
performDeferredLoadOnStartup：延迟启动
这里面会延迟启动 TomcatEmbeddedContext
private void performDeferredLoadOnStartup() {
try {
for (Container child : this.tomcat.getHost().findChildren()) {
if (child instanceof TomcatEmbeddedContext) {
// 延迟启动Context
((TomcatEmbeddedContext) child).deferredLoadOnStartup();
}
}
}
catch (Exception ex) {
if (ex instanceof WebServerException) {
throw (WebServerException) ex;
}
throw new WebServerException("Unable to start embedded Tomcat connectors", ex);
}
}以上就是“ServletWebServerApplicationContext如何创建Web容器Tomcat”这篇文章的所有内容，感谢各位的阅读！相信大家阅读完这篇文章都有很大的收获，小编每天都会为大家更新不同的知识，如果还想学习更多的知识，请关注亿速云行业资讯频道。
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