尚硅谷springboot学习27-使用外置servlet容器

　　嵌入式Servlet容器：应用打成可执行的jar

　　​ 优点：简单、便携；

　　​ 缺点：默认不支持JSP、优化定制比较复杂（使用定制器【ServerProperties、自定义EmbeddedServletContainerCustomizer】，自己编写嵌入式Servlet容器的创建工厂【EmbeddedServletContainerFactory】）；

　　外置的Servlet容器：外面安装Tomcat---应用war包的方式打包；

　　步骤

　　1）、必须创建一个war项目；（利用idea创建好目录结构）

　　2）、将嵌入式的Tomcat指定为provided；

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-tomcat</artifactId>
   <scope>provided</scope>
</dependency>

　　3）、必须编写一个SpringBootServletInitializer的子类，并调用configure方法

public class ServletInitializer extends SpringBootServletInitializer {

   @Override
   protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
       //传入SpringBoot应用的主程序
      return application.sources(SpringBoot04WebJspApplication.class);
   }

}

　　4）、启动服务器就可以使用；

　　原理

　　jar包：执行SpringBoot主类的main方法，启动ioc容器，创建嵌入式的Servlet容器；

　　war包：启动服务器，服务器启动SpringBoot应用【SpringBootServletInitializer】，启动ioc容器；

　　servlet3.0（Spring注解版）：

　　8.2.4 Shared libraries / runtimes pluggability：

　　规则：

　　​ 1）、服务器启动（web应用启动）会创建当前web应用里面每一个jar包里面ServletContainerInitializer实例：

　　​ 2）、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

​　　 3）、还可以使用@HandlesTypes，在应用启动的时候加载我们感兴趣的类；

　　流程：

　　1）、启动Tomcat

　　2）、org\springframework\spring-web\4.3.14.RELEASE\spring-web-4.3.14.RELEASE.jar!\META-INF\services\javax.servlet.ServletContainerInitializer：

Spring的web模块里面有这个文件：org.springframework.web.SpringServletContainerInitializer

　　3）、SpringServletContainerInitializer将@HandlesTypes(WebApplicationInitializer.class)标注的所有这个类型的类都传入到onStartup方法的Set<Class<?>>；为这些WebApplicationInitializer类型的类创建实例；

　　4）、每一个WebApplicationInitializer都调用自己的onStartup；

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" 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　　5）、相当于我们的SpringBootServletInitializer的类会被创建对象，并执行onStartup方法

　　6）、SpringBootServletInitializer实例执行onStartup的时候会createRootApplicationContext；创建容器

protected WebApplicationContext createRootApplicationContext(
      ServletContext servletContext) {
    //1、创建SpringApplicationBuilder
   SpringApplicationBuilder builder = createSpringApplicationBuilder();
   StandardServletEnvironment environment = new StandardServletEnvironment();
   environment.initPropertySources(servletContext, null);
   builder.environment(environment);
   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(AnnotationConfigEmbeddedWebApplicationContext.class);

    //调用configure方法，子类重写了这个方法，将SpringBoot的主程序类传入了进来
   builder = configure(builder);

    //使用builder创建一个Spring应用
   SpringApplication application = builder.build();
   if (application.getSources().isEmpty() && AnnotationUtils
         .findAnnotation(getClass(), Configuration.class) != null) {
      application.getSources().add(getClass());
   }
   Assert.state(!application.getSources().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.getSources().add(ErrorPageFilterConfiguration.class);
   }
    //启动Spring应用
   return run(application);
}

　　7）、Spring的应用就启动并且创建IOC容器

public ConfigurableApplicationContext run(String... args) {
   StopWatch stopWatch = new StopWatch();
   stopWatch.start();
   ConfigurableApplicationContext context = null;
   FailureAnalyzers analyzers = null;
   configureHeadlessProperty();
   SpringApplicationRunListeners listeners = getRunListeners(args);
   listeners.starting();
   try {
      ApplicationArguments applicationArguments = new DefaultApplicationArguments(
            args);
      ConfigurableEnvironment environment = prepareEnvironment(listeners,
            applicationArguments);
      Banner printedBanner = printBanner(environment);
      context = createApplicationContext();
      analyzers = new FailureAnalyzers(context);
      prepareContext(context, environment, listeners, applicationArguments,
            printedBanner);

       //刷新IOC容器
      refreshContext(context);
      afterRefresh(context, applicationArguments);
      listeners.finished(context, null);
      stopWatch.stop();
      if (this.logStartupInfo) {
         new StartupInfoLogger(this.mainApplicationClass)
               .logStarted(getApplicationLog(), stopWatch);
      }
      return context;
   }
   catch (Throwable ex) {
      handleRunFailure(context, listeners, analyzers, ex);
      throw new IllegalStateException(ex);
   }
}

　　启动Servlet容器，再启动SpringBoot应用