（15）spring boot 注册3大组件

蔚落 2022-02-03 11:13 125阅读 0赞

# 3大组件:   ** Servlet****，****Filter****，****Listener** #

先展示结构:

![20190509123446158.png][]

![20190509123446156.png][]

# **1.Servlet** #

***s1***:在MyServlet中写像以前那样的servlet，同样重写doGet()和doPost()。

类要求重写HttpServlet.

public class MyServlet extends HttpServlet {
    
        @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 My Servlet!");
    
        }
    
    }

***s2:*在MyServlerConfig（注意，该类必须得加上配置类标示：@Configuration）中：**

@Bean
    
    public ServletRegistrationBean myServlet(){
    
        ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean(new MyServlet(),"/myServlet");
    
        return servletRegistrationBean;
    
    }

@Bean 别忘了写了！

这样，在访问/myServlet时，就会在浏览器界面打印出来“Hello My Servlet”

# **2.Filter** #

**s1****：**在MyFilter中写上以前Filter方法：

public class filter 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("My Filter processing....");
    
            //放行
    
            filterChain.doFilter(servletRequest,servletResponse);
    
    
    
        }
    
    
    
        @Override
    
        public void destroy() {
    
    
    
        }
    
    }

**s2**：还是要在MyServer中注册：

@Bean
    
    public FilterRegistrationBean myFilter(){
    
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
    
        registrationBean.setFilter(new filter());
    
        registrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
    
        return registrationBean;
    
    }

***注意implents的是javax.servlet下的Filter!***

# **3.Listener** #

s1：

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

s2：

@Bean
    
    public ServletListenerRegistrationBean myListener(){
    
        ServletListenerRegistrationBean<MyListener> registrationBean = new ServletListenerRegistrationBean<>(new MyListener());
    
        return registrationBean;
    
    }

[20190509123446158.png]: /images/20220203/adda5dcea6ee496480e1e9d2718489e0.png
[20190509123446156.png]: /images/20220203/c3487deabb7b468e8ed026e93ac6bd10.png