SpringBoot内置容器相关知识

SpringBoot嵌入式容器相关知识

1、配置嵌入式Servlet容器

SpringBoot默认使用Tomcat作为嵌入式的Servlet容器；

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• 修改和server有关的配置（ServerProperties类[也是EmbeddedServletContainerCustomizer]）；

server.port=8081
server.context-path=/crud

server.tomcat.uri-encoding=UTF-8

//通用的Servlet容器设置
server.xxx
//Tomcat的设置
server.tomcat.xxx

• 编写一个EmbeddedServletContainerCustomizer：嵌入式的Servlet容器的定制器；来修改Servlet容器的配置

•   @Bean  //一定要将这个定制器加入到容器中
    public EmbeddedServletContainerCustomizer embeddedServletContainerCustomizer(){
        return new EmbeddedServletContainerCustomizer() {
  
            //定制嵌入式的Servlet容器相关的规则
            @Override
            public void customize(ConfigurableEmbeddedServletContainer container) {
                container.setPort(8083);
            }
        };
    }
  

2、 注册三大Servlet组件

由于SpringBoot默认是以jar包的方式启动嵌入式的Servlet容器来启动SpringBoot的web应用，没有web.xml文件，注册三大组件用以下方式来注册

注册Servlet：使用ServletRegistrationBean

// 配置类
@Configuration
public class MyServerConfig {
    @Bean
    public ServletRegistrationBean myServlet(){
      ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(),"/myServlet");
      // 在注册时都可以设置Servlet的属性,如registrationBean.setLoadOnStartup(1);
      return registrationBean;
    }
}

// 自定义的Servlet
public class MyServlet extends HttpServlet {

    //处理get请求
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write("Hello MyServlet");
    }
}

注册Filter：使用FilterRegistrationBean

// 配置类
@Configuration
public class MyServerConfig {
    @Bean
    public FilterRegistrationBean myFilter(){
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        registrationBean.setFilter(new MyFilter());
        registrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
        return registrationBean;
    }
}



public class MyFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("MyFilter process...");
        chain.doFilter(request,response);

    }

    @Override
    public void destroy() {

    }
}

注册Listener：使用ListenerRegistrationBean

// 配置类
@Configuration
public class MyServerConfig {
    @Bean
    public ServletListenerRegistrationBean myListener(){
        ServletListenerRegistrationBean<MyListener> registrationBean = new ServletListenerRegistrationBean<>(new MyListener());
        return registrationBean;
    }
}


public class MyListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("contextInitialized...web应用启动");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        System.out.println("contextDestroyed...当前web项目销毁");
    }
}

SpringBoot帮我们自动SpringMVC的时候，自动的注册SpringMVC的前端控制器；DIspatcherServlet；也是使用这种方式来配置：

DispatcherServletAutoConfiguration类源码：

  @Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)
  @ConditionalOnBean(value = DispatcherServlet.class, name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
  public ServletRegistrationBean dispatcherServletRegistration(
        DispatcherServlet dispatcherServlet) {
     ServletRegistrationBean registration = new ServletRegistrationBean(
           dispatcherServlet, this.serverProperties.getServletMapping());
      //默认拦截： /  所有请求；包静态资源，但是不拦截jsp请求；   /*会拦截jsp
      //可以通过server.servletPath来修改SpringMVC前端控制器默认拦截的请求路径
    
     registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
     registration.setLoadOnStartup(
           this.webMvcProperties.getServlet().getLoadOnStartup());
     if (this.multipartConfig != null) {
        registration.setMultipartConfig(this.multipartConfig);
     }
     return registration;
  }

3、切换为其他嵌入式Servlet容器

• Jetty(长连接)

• Undertow(不支持JSP)

  
    <!-- 引入web模块 -->
    <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>
         // 将Tomcat从Pom文件中移除
       <exclusions>
          <exclusion>
             <artifactId>spring-boot-starter-tomcat</artifactId>
             <groupId>org.springframework.boot</groupId>
          </exclusion>
       </exclusions>
    </dependency>
  
  
  	// 引入需要的Servlet容器,这里也可以引入Undertow
    <dependency>
       <artifactId>spring-boot-starter-jetty</artifactId>
       <groupId>org.springframework.boot</groupId>
    </dependency>