使用内置 tomcat 启动
配置案例
启动方式
IDEA 中 main 函数启动
mvn springboot-run
java -jar XXX.jar 使用这种方式时，为保证服务在后台运行，会使用 nohup
nohup java -jar -Xms128m -Xmx128m -Xss256k -XX:+PrintGCDetails -XX:+PrintHeapAtGC -Xloggc:/data/log/web-gc.log web.jar >/data/log/web.log &
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使用 java -jar 默认情况下，不会启动任何嵌入式 Application Server，该命令只是启动一个执行 jar main 的 JVM 进程，当 spring-boot-starter-web 包含嵌入式 tomcat 服务器依赖项时，执行 java -jar 则会启动 Application Server
配置内置 tomcat 属性
关于 Tomcat 的属性都在 org.springframework.boot.autoconfigure.web.ServerProperties 配置类中做了定义，我们只需在 application.properties 配置属性做配置即可。通用的 Servlet 容器配置都以 server 作为前缀
#配置程序端口，默认为8080server.port= 8080#用户会话session过期时间，以秒为单位server.session.timeout=#配置默认访问路径，默认为/server.context-path=
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而 Tomcat 特有配置都以 server.tomcat 作为前缀
# 配置Tomcat编码,默认为UTF-8server.tomcat.uri-encoding=UTF-8# 配置最大线程数server.tomcat.max-threads=1000
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注意：使用内置 tomcat 不需要有 tomcat-embed-jasper 和 spring-boot-starter-tomcat 依赖，因为在 spring-boot-starter-web 依赖中已经集成了 tomcat
原理
从 main 函数说起
public static ConfigurableApplicationContext run(Class<?> primarySource, String... args) { return run(new Class[]{primarySource}, args);} // 这里run方法返回的是ConfigurableApplicationContextpublic static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) { return (new SpringApplication(primarySources)).run(args);}
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public ConfigurableApplicationContext run(String... args) { ConfigurableApplicationContext context = null; Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList(); this.configureHeadlessProperty(); SpringApplicationRunListeners listeners = this.getRunListeners(args); listeners.starting(); Collection exceptionReporters; try { ApplicationArguments applicationArguments = new DefaultApplicationArguments(args); ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments); this.configureIgnoreBeanInfo(environment); //打印banner，这里可以自己涂鸦一下，换成自己项目的logo Banner printedBanner = this.printBanner(environment); //创建应用上下文 context = this.createApplicationContext(); exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context); //预处理上下文 this.prepareContext(context, environment, listeners, applicationArguments, printedBanner); //刷新上下文 this.refreshContext(context); //再刷新上下文 this.afterRefresh(context, applicationArguments); listeners.started(context); this.callRunners(context, applicationArguments); } catch (Throwable var10) { } try { listeners.running(context); return context; } catch (Throwable var9) { }}
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既然我们想知道 tomcat 在 SpringBoot 中是怎么启动的，那么 run 方法中，重点关注创建应用上下文（createApplicationContext）和刷新上下文（refreshContext）。
创建上下文
//创建上下文protected ConfigurableApplicationContext createApplicationContext() { Class<?> contextClass = this.applicationContextClass; if (contextClass == null) { try { switch(this.webApplicationType) { case SERVLET: //创建AnnotationConfigServletWebServerApplicationContext contextClass = Class.forName("org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext"); break; case REACTIVE: contextClass = Class.forName("org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext"); break; default: contextClass = Class.forName("org.springframework.context.annotation.AnnotationConfigApplicationContext"); } } catch (ClassNotFoundException var3) { throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass", var3); } } return (ConfigurableApplicationContext)BeanUtils.instantiateClass(contextClass);}
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这里会创建 AnnotationConfigServletWebServerApplicationContext 类。而 AnnotationConfigServletWebServerApplicationContext 类继承了 ServletWebServerApplicationContext，而这个类是最终集成了 AbstractApplicationContext。
刷新上下文
//SpringApplication.java//刷新上下文private void refreshContext(ConfigurableApplicationContext context) { this.refresh(context); if (this.registerShutdownHook) { try { context.registerShutdownHook(); } catch (AccessControlException var3) { } }} //这里直接调用最终父类AbstractApplicationContext.refresh()方法protected void refresh(ApplicationContext applicationContext) { ((AbstractApplicationContext)applicationContext).refresh();}
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//AbstractApplicationContext.javapublic void refresh() throws BeansException, IllegalStateException { synchronized(this.startupShutdownMonitor) { this.prepareRefresh(); ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory(); this.prepareBeanFactory(beanFactory); try { this.postProcessBeanFactory(beanFactory); this.invokeBeanFactoryPostProcessors(beanFactory); this.registerBeanPostProcessors(beanFactory); this.initMessageSource(); this.initApplicationEventMulticaster(); //调用各个子类的onRefresh()方法，也就说这里要回到子类：ServletWebServerApplicationContext，调用该类的onRefresh()方法 this.onRefresh(); this.registerListeners(); this.finishBeanFactoryInitialization(beanFactory); this.finishRefresh(); } catch (BeansException var9) { this.destroyBeans(); this.cancelRefresh(var9); throw var9; } finally { this.resetCommonCaches(); } }}
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//ServletWebServerApplicationContext.java//在这个方法里看到了熟悉的面孔，this.createWebServer，神秘的面纱就要揭开了。protected void onRefresh() { super.onRefresh(); try { this.createWebServer(); } catch (Throwable var2) { }} //ServletWebServerApplicationContext.java//这里是创建webServer，但是还没有启动tomcat，这里是通过ServletWebServerFactory创建，那么接着看下ServletWebServerFactoryprivate void createWebServer() { WebServer webServer = this.webServer; ServletContext servletContext = this.getServletContext(); if (webServer == null && servletContext == null) { ServletWebServerFactory factory = this.getWebServerFactory(); this.webServer = factory.getWebServer(new ServletContextInitializer[]{this.getSelfInitializer()}); } else if (servletContext != null) { try { this.getSelfInitializer().onStartup(servletContext); } catch (ServletException var4) { } } this.initPropertySources();} //接口public interface ServletWebServerFactory { WebServer getWebServer(ServletContextInitializer... initializers);} //实现AbstractServletWebServerFactoryJettyServletWebServerFactoryTomcatServletWebServerFactoryUndertowServletWebServerFactory
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这里 ServletWebServerFactory 接口有 4 个实现类，对应着四种容器：
而其中我们常用的有两个：TomcatServletWebServerFactory 和 JettyServletWebServerFactory。
//TomcatServletWebServerFactory.java//这里我们使用的tomcat，所以我们查看TomcatServletWebServerFactory。到这里总算是看到了tomcat的踪迹。@Overridepublic WebServer getWebServer(ServletContextInitializer... initializers) { Tomcat tomcat = new Tomcat(); File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat"); tomcat.setBaseDir(baseDir.getAbsolutePath()); //创建Connector对象 Connector connector = new Connector(this.protocol); tomcat.getService().addConnector(connector); customizeConnector(connector); tomcat.setConnector(connector); tomcat.getHost().setAutoDeploy(false); configureEngine(tomcat.getEngine()); for (Connector additionalConnector : this.additionalTomcatConnectors) { tomcat.getService().addConnector(additionalConnector); } prepareContext(tomcat.getHost(), initializers); return getTomcatWebServer(tomcat);} protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) { return new TomcatWebServer(tomcat, getPort() >= 0);} //Tomcat.java//返回Engine容器，看到这里，如果熟悉tomcat源码的话，对engine不会感到陌生。public Engine getEngine() { Service service = getServer().findServices()[0]; if (service.getContainer() != null) { return service.getContainer(); } Engine engine = new StandardEngine(); engine.setName( "Tomcat" ); engine.setDefaultHost(hostname); engine.setRealm(createDefaultRealm()); service.setContainer(engine); return engine;}//Engine是最高级别容器，Host是Engine的子容器，Context是Host的子容器，Wrapper是Context的子容器
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getWebServer 这个方法创建了 Tomcat 对象，并且做了两件重要的事情：把 Connector 对象添加到 tomcat 中，configureEngine(tomcat.getEngine());
getWebServer 方法返回的是 TomcatWebServer。
//TomcatWebServer.java//这里调用构造函数实例化TomcatWebServerpublic TomcatWebServer(Tomcat tomcat, boolean autoStart) { Assert.notNull(tomcat, "Tomcat Server must not be null"); this.tomcat = tomcat; this.autoStart = autoStart; initialize();} private void initialize() throws WebServerException { //在控制台会看到这句日志 logger.info("Tomcat initialized with port(s): " + getPortsDescription(false)); synchronized (this.monitor) { try { addInstanceIdToEngineName(); Context context = findContext(); context.addLifecycleListener((event) -> { if (context.equals(event.getSource()) && Lifecycle.START_EVENT.equals(event.getType())) { removeServiceConnectors(); } }); //===启动tomcat服务=== this.tomcat.start(); rethrowDeferredStartupExceptions(); try { ContextBindings.bindClassLoader(context, context.getNamingToken(), getClass().getClassLoader()); } catch (NamingException ex) { } //开启阻塞非守护进程 startDaemonAwaitThread(); } catch (Exception ex) { stopSilently(); destroySilently(); throw new WebServerException("Unable to start embedded Tomcat", ex); } }}
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//Tomcat.javapublic void start() throws LifecycleException { getServer(); server.start();}//这里server.start又会回到TomcatWebServer的public void stop() throws LifecycleException { getServer(); server.stop();}
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//TomcatWebServer.java//启动tomcat服务@Overridepublic void start() throws WebServerException { synchronized (this.monitor) { if (this.started) { return; } try { addPreviouslyRemovedConnectors(); Connector connector = this.tomcat.getConnector(); if (connector != null && this.autoStart) { performDeferredLoadOnStartup(); } checkThatConnectorsHaveStarted(); this.started = true; //在控制台打印这句日志，如果在yml设置了上下文，这里会打印 logger.info("Tomcat started on port(s): " + getPortsDescription(true) + " with context path '" + getContextPath() + "'"); } catch (ConnectorStartFailedException ex) { stopSilently(); throw ex; } catch (Exception ex) { throw new WebServerException("Unable to start embedded Tomcat server", ex); } finally { Context context = findContext(); ContextBindings.unbindClassLoader(context, context.getNamingToken(), getClass().getClassLoader()); } }} //关闭tomcat服务@Overridepublic void stop() throws WebServerException { synchronized (this.monitor) { boolean wasStarted = this.started; try { this.started = false; try { stopTomcat(); this.tomcat.destroy(); } catch (LifecycleException ex) { } } catch (Exception ex) { throw new WebServerException("Unable to stop embedded Tomcat", ex); } finally { if (wasStarted) { containerCounter.decrementAndGet(); } } }}
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使用外置 tomcat 部署
配置案例
外置Tomcat启动SpringBoot源码点击这里
继承 SpringBootServletInitializer
方式一：启动类继承 SpringBootServletInitializer 实现 configure：
@SpringBootApplicationpublic class SpringBootHelloWorldTomcatApplication extends SpringBootServletInitializer { @Override protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) { return builder.sources(Application.class); }}
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这个类的作用与在 web.xml 中配置负责初始化 Spring 应用上下文的监听器作用类似，只不过在这里不需要编写额外的 XML 文件了。
方式二：新增加一个类继承 SpringBootServletInitializer 实现 configure：
public class ServletInitializer extends SpringBootServletInitializer { @Override protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) { //此处的Application.class为带有@SpringBootApplication注解的启动类 return builder.sources(Application.class); }}
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pom.xml 修改 tomcat 相关的配置
首先需要将 jar 变成 war <packaging>war</packaging>
如果要将最终的打包形式改为 war 的话，还需要对 pom.xml 文件进行修改，因为 spring-boot-starter-web 中包含内嵌的 tomcat 容器，所以直接部署在外部容器会冲突报错。因此需要将内置 tomcat 排除
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <exclusions> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </exclusion> </exclusions></dependency>
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在这里需要移除对嵌入式 Tomcat 的依赖，这样打出的 war 包中，在 lib 目录下才不会包含 Tomcat 相关的 jar 包，否则将会出现启动错误。
但是移除了 tomcat 后，原始的 sevlet 也被移除了，因此还需要额外引入 servet 的包
<dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.0.1</version></dependency>
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注意的问题
此时打成的包的名称应该和 application.properties 的 server.context-path=/test 保持一致
<build> <finalName>test</finalName></build>
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如果不一样发布到 tomcat 的 webapps 下上下文会变化
原理
tomcat 不会主动去启动 springboot 应用 ，， 所以 tomcat 启动的时候肯定调用了 SpringBootServletInitializer 的 SpringApplicationBuilder ， 就会启动 springboot。
ServletContainerInitializer 的实现放在 jar 包的 META-INF/services 文件夹下，有一个名为 javax.servlet.ServletContainerInitializer 的文件，内容就是 ServletContainerInitializer 的实现类的全类名。当 servlet 容器启动时候就会去该文件中找到 ServletContainerInitializer 的实现类，从而创建它的实例调用 onstartUp。这里就是用了SPI机制
HandlesTypes(WebApplicationInitializer.class)
@HandlesTypes 传入的类为 ServletContainerInitializer 感兴趣的
容器会自动在 classpath 中找到 WebApplicationInitializer，会传入到 onStartup 方法的 webAppInitializerClasses 中
Set<Class<?>> webAppInitializerClasses这里面也包括之前定义的 TomcatStartSpringBoot
@HandlesTypes(WebApplicationInitializer.class)public class SpringServletContainerInitializer implements ServletContainerInitializer {
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@Overridepublic void onStartup(@Nullable Set<Class<?>> webAppInitializerClasses, ServletContext servletContext) throws ServletException {
List<WebApplicationInitializer> initializers = new LinkedList<>();
if (webAppInitializerClasses != null) { for (Class<?> waiClass : webAppInitializerClasses) { // 如果不是接口 不是抽象 跟WebApplicationInitializer有关系 就会实例化 if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) && WebApplicationInitializer.class.isAssignableFrom(waiClass)) { try { initializers.add((WebApplicationInitializer) ReflectionUtils.accessibleConstructor(waiClass).newInstance()); } catch (Throwable ex) { throw new ServletException("Failed to instantiate WebApplicationInitializer class", ex); } } } }
if (initializers.isEmpty()) { servletContext.log("No Spring WebApplicationInitializer types detected on classpath"); return; }
servletContext.log(initializers.size() + " Spring WebApplicationInitializers detected on classpath"); // 排序 AnnotationAwareOrderComparator.sort(initializers); for (WebApplicationInitializer initializer : initializers) { initializer.onStartup(servletContext); }}
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@Overridepublic void onStartup(ServletContext servletContext) throws ServletException { // Logger initialization is deferred in case an ordered // LogServletContextInitializer is being used this.logger = LogFactory.getLog(getClass()); WebApplicationContext rootApplicationContext = createRootApplicationContext(servletContext); if (rootApplicationContext != null) { servletContext.addListener(new SpringBootContextLoaderListener(rootApplicationContext, servletContext)); } else { this.logger.debug("No ContextLoaderListener registered, as createRootApplicationContext() did not " + "return an application context"); }}
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SpringBootServletInitializer
protected WebApplicationContext createRootApplicationContext(ServletContext servletContext) { SpringApplicationBuilder builder = createSpringApplicationBuilder(); builder.main(getClass()); ApplicationContext parent = getExistingRootWebApplicationContext(servletContext); if (parent != null) { this.logger.info("Root context already created (using as parent)."); servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, null); builder.initializers(new ParentContextApplicationContextInitializer(parent)); } builder.initializers(new ServletContextApplicationContextInitializer(servletContext)); builder.contextClass(AnnotationConfigServletWebServerApplicationContext.class); // 调用configure builder = configure(builder); //① builder.listeners(new WebEnvironmentPropertySourceInitializer(servletContext)); SpringApplication application = builder.build();//② if (application.getAllSources().isEmpty() && MergedAnnotations.from(getClass(), SearchStrategy.TYPE_HIERARCHY).isPresent(Configuration.class)) { application.addPrimarySources(Collections.singleton(getClass())); } Assert.state(!application.getAllSources().isEmpty(), "No SpringApplication sources have been defined. Either override the " + "configure method or add an @Configuration annotation"); // Ensure error pages are registered if (this.registerErrorPageFilter) { application.addPrimarySources(Collections.singleton(ErrorPageFilterConfiguration.class)); } application.setRegisterShutdownHook(false); return run(application);//③}
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① 当调用 configure 就会来到 TomcatStartSpringBoot .configure，将 Springboot 启动类传入到 builder.source
@Overrideprotected SpringApplicationBuilder configure(SpringApplicationBuilder builder) { return builder.sources(Application.class);}
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② 调用 SpringApplication application = builder.build(); 就会根据传入的 Springboot 启动类来构建一个 SpringApplication
public SpringApplication build(String... args) { configureAsChildIfNecessary(args); this.application.addPrimarySources(this.sources); return this.application;}
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③ 调用 return run(application); 就会启动 springboot 应用
protected WebApplicationContext run(SpringApplication application) { return (WebApplicationContext) application.run();}
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也就相当于 Main 函数启动：
public static void main(String[] args) { SpringApplication.run(Application.class, args);}
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之后的流程就与上面 使用内置 Tomcat 的 Main 函数一致了
文章转载自：seven97_top
原文链接：https://www.cnblogs.com/seven97-top/p/18671729
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