Spring Boot之注册servlet三大组件

由于Spring Boot默认是以jar包的形式启动嵌入式的Servlet容器来启动Spring Boot的web应用是，没有web.xml配置文件
注册三大组件用以下方式

ServletRegistrationBean
FilterRegistrationBean
ServletListenerRegistrationBean

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一、注册一个ServletRegistrationBean

1.定义一个Servlet类

//向页面输出一句hello
public class HttpServlet extends javax.servlet.http.HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.getWriter().write("hello");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

2.编写一个Servlet配置类

@Configuration
public class MyServerConfig {
    //注册三大组件
    //注意加上@Bean注解，否者无法加入到容器中
    @Bean
    public ServletRegistrationBean myServlet(){
        ServletRegistrationBean servlet = new ServletRegistrationBean(new HttpServlet(), "/myServlet");
        return servlet;
    }

3.Spring Boot配置文件

server.port=8081
server.servlet.context-path=/boot
server.tomcat.uri-encoding=UTF-8

4.启动主配置文件访问http://localhost:8081/boot/myServlet

这样就生效了

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二、注册一个FilterRegistrationBean

1.定义一个Filter类

public class MyFilter implements Filter {

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

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("success");
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {

    }
}

2.编写一个filter配置类

@Configuration
public class MyServerConfig {
    //注册三大组件

    @Bean
    public FilterRegistrationBean filterRegistrationBean(){
        FilterRegistrationBean re = new FilterRegistrationBean();
        re.setFilter(new MyFilter());
        re.setUrlPatterns(Arrays.asList("/hello","/filter"));
        return re;
    }

3.启动访问http://localhost:8081/boot/filter

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ServletListenerRegistrationBean的使用类似于以上两种组件

Spring Boot 帮我们自动注册了SpringMVC的核心控制器DispatcherServlet，其注册方式类似于以上两种注册