20、springboot——使用外置的tomcat服务器

嵌入式Servlet容器:应用打成可执行的j ar
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
 
创建工程的时候使用war包

 添加xml配置文件

 

 

 
 添加外部的服务器:

 

 完成hello.jsp页面的跳转

 

hello.jsp

 

test.jsp

 test.java

 

 测试:

 

总结:
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(IDEA创建的时候回自带)

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)
章节: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

流程:

1)、启动Tomcat
2)、orgspringframeworkspring-web4.3.14.RELEASEspring-web-         5.1.3.RELEASE.jar!METAINFservicesjavax.servlet.ServletContainerInitializer:
  Spring的web模块里面有这个文件:

 

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>;为这些WebApplicationInitializer类型的类创建实例;
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@HandlesTypes({WebApplicationInitializer.class})
public class SpringServletContainerInitializer implements ServletContainerInitializer {
    public SpringServletContainerInitializer() {
    }

    public void onStartup(@Nullable Set<Class<?>> webAppInitializerClasses, ServletContext servletContext) throws ServletException {
        List<WebApplicationInitializer> initializers = new LinkedList();
        Iterator var4;
        if (webAppInitializerClasses != null) {
            var4 = webAppInitializerClasses.iterator();

            while(var4.hasNext()) {
                Class<?> waiClass = (Class)var4.next();
                if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) && WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
                    try {
                        initializers.add((WebApplicationInitializer)ReflectionUtils.accessibleConstructor(waiClass, new Class[0]).newInstance());
                    } catch (Throwable var7) {
                        throw new ServletException("Failed to instantiate WebApplicationInitializer class", var7);
                    }
                }
            }
        }

        if (initializers.isEmpty()) {
            servletContext.log("No Spring WebApplicationInitializer types detected on classpath");
        } else {
            servletContext.log(initializers.size() + " Spring WebApplicationInitializers detected on classpath");
            AnnotationAwareOrderComparator.sort(initializers);
            var4 = initializers.iterator();

            while(var4.hasNext()) {
                WebApplicationInitializer initializer = (WebApplicationInitializer)var4.next();
                initializer.onStartup(servletContext);
}}}}
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4)、每一个WebApplicationInitializer都调用自己的onStartup;
WebApplicationInitializer的实现

 

是我们自己的Servletinitializer类
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
public class ServletInitializer extends SpringBootServletInitializer {
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(WebJspApplication.class);
    }
}

 SpringBootServletInitializer.java

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public void onStartup(ServletContext servletContext) throws ServletException {
    this.logger = LogFactory.getLog(this.getClass());
    WebApplicationContext rootAppContext = this.createRootApplicationContext(servletContext);
    if (rootAppContext != null) {
        servletContext.addListener(new ContextLoaderListener(rootAppContext) {
            public void contextInitialized(ServletContextEvent event) {
            }
        });
    } else {
        this.logger.debug("No ContextLoaderListener registered, as createRootApplicationContext() did not return an application context");
    }
}

.....
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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);
}
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7)、Spring的应用就启动并且创建IOC容器

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public ConfigurableApplicationContext run(String... args) {
    StopWatch stopWatch = new StopWatch();
    stopWatch.start();
    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);
        Banner printedBanner = this.printBanner(environment);
        context = this.createApplicationContext();
        exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);
        this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
       
//刷新容器的初始化
 this.refreshContext(context);
        this.afterRefresh(context, applicationArguments);
        stopWatch.stop();
        if (this.logStartupInfo) {
            (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
        }

        listeners.started(context);
        this.callRunners(context, applicationArguments);
    } catch (Throwable var10) {
        this.handleRunFailure(context, var10, exceptionReporters, listeners);
        throw new IllegalStateException(var10);
    }

    try {
        listeners.running(context);
        return context;
    } catch (Throwable var9) {
        this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null);
        throw new IllegalStateException(var9);
    }
}
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原文地址:https://www.cnblogs.com/lyh233/p/12541552.html