SpringBoot---web 应用开发-Servlets, Filters, listeners

绝地灬酷狼 2022-05-11 15:10 234阅读 0赞

> **一.**Web 开发使用 Controller 基本上可以完成大部分需求，但是我们还可能会用到 Servlet、 Filter、Listener 等等。
> 
> **二.**在 spring boot 中的三种实现方式
> 
>        (1) 1.通过注册 ServletRegistrationBean、 FilterRegistrationBean 和 ServletListenerRegistrationBean 获得控制,
> 
>          CustomServlet,java 如下：
> 
>     package com.nyist.demo.utils.servlet;
>     
>     import javax.servlet.ServletException;
>     import javax.servlet.http.HttpServlet;
>     import javax.servlet.http.HttpServletRequest;
>     import javax.servlet.http.HttpServletResponse;
>     import java.io.IOException;
>     
>     
>     public class CustomServlet extends HttpServlet {
>     
>      private static final long serialVersionUID = 1L; 
>      
>      @Override 
>      protected void doGet(HttpServletRequest request, HttpServletResponse response)
>        throws ServletException, IOException {
>        System.out.println("servlet get method");
>        doPost(request, response);
>      } 
>      
>      @Override 
>      protected void doPost(HttpServletRequest request, HttpServletResponse response) 
>        throws ServletException, IOException { 
>        System.out.println("servlet post method");
>        response.getWriter().write("hello world");
>      } 
>      
>     }
> 
>       在启动类中注册ServletRegistrationBean 获得访问路径
> 
>     package com.nyist.demo;
>     
>     import com.nyist.demo.utils.filter.CustomFilter;
>     import com.nyist.demo.utils.listener.CustomListener;
>     import com.nyist.demo.utils.servlet.CustomServlet;
>     import org.springframework.boot.SpringApplication;
>     import org.springframework.boot.autoconfigure.SpringBootApplication;
>     import org.springframework.boot.web.servlet.FilterRegistrationBean;
>     import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
>     import org.springframework.boot.web.servlet.ServletRegistrationBean;
>     import org.springframework.context.annotation.Bean;
>     
>     import javax.swing.*;
>     
>     @SpringBootApplication
>     public class DemoApplication {
>     
>         @Bean
>         public ServletRegistrationBean servletRegistrationBean() {
>             return new ServletRegistrationBean(new CustomServlet(), "/nyist");
>         }
>     }
> 
>     2. 定义一个CustomFileterlei类 实现Filter接口
> 
>         CustomFilter.java 如下：
> 
>     package com.nyist.demo.utils.filter; /**
>      * 自定义 filter 
>      *  
>      * @author wujing 
>      */
>     
>     import javax.servlet.*;
>     import java.io.IOException;
>     
>     public class CustomFilter implements Filter { 
>      
>       @Override
>       public void init(FilterConfig filterConfig) throws ServletException {
>         System.out.println("init filter");
>       }
>     
>       @Override
>       public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
>         throws IOException, ServletException {
>         System.out.println("do filter");
>         chain.doFilter(request, response);
>       }
>     
>       @Override
>       public void destroy() {
>         System.out.println("destroy filter");
>       }
>     
>     }
> 
>       在启动类中注册，FilterRegistrationBean 来设置需要拦截的servlet
> 
>     package com.nyist.demo;
>     
>     import com.nyist.demo.utils.filter.CustomFilter;
>     import com.nyist.demo.utils.listener.CustomListener;
>     import com.nyist.demo.utils.servlet.CustomServlet;
>     import org.springframework.boot.SpringApplication;
>     import org.springframework.boot.autoconfigure.SpringBootApplication;
>     import org.springframework.boot.web.servlet.FilterRegistrationBean;
>     import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
>     import org.springframework.boot.web.servlet.ServletRegistrationBean;
>     import org.springframework.context.annotation.Bean;
>     
>     import javax.swing.*;
>     
>     @SpringBootApplication
>     public class DemoApplication {
>     
>         @Bean
>         public FilterRegistrationBean filterRegistrationBean() {
>             return new FilterRegistrationBean(new CustomFilter());
>         }
>     }
> 
>      3.CustomListener 实现 Listener 接口，用来监听servlet
> 
>     package com.nyist.demo.utils.listener;
>     
>     import javax.servlet.ServletContextEvent;
>     import javax.servlet.ServletContextListener;
>     
>     /**
>      * 自定义 listener 
>      *  
>      * @author wujing 
>      */ 
>     public class CustomListener implements ServletContextListener {
>      
>        @Override
>        public void contextInitialized(ServletContextEvent sce) {
>         System.out.println("contextInitialized");
>        }
>     
>        @Override
>        public void contextDestroyed(ServletContextEvent sce) {
>         System.out.println("contextDestroyed");
>        }
>      
>     }
> 
>         在启动类注册，ListenerRegistrationBean 
> 
>     package com.nyist.demo;
>     
>     import com.nyist.demo.utils.filter.CustomFilter;
>     import com.nyist.demo.utils.listener.CustomListener;
>     import com.nyist.demo.utils.servlet.CustomServlet;
>     import org.springframework.boot.SpringApplication;
>     import org.springframework.boot.autoconfigure.SpringBootApplication;
>     import org.springframework.boot.web.servlet.FilterRegistrationBean;
>     import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
>     import org.springframework.boot.web.servlet.ServletRegistrationBean;
>     import org.springframework.context.annotation.Bean;
>     
>     import javax.swing.*;
>     
>     @SpringBootApplication
>     public class DemoApplication {
>     
>         @Bean
>         public ServletListenerRegistrationBean<CustomListener> servletListenerRegistrationBean() {
>             return new ServletListenerRegistrationBean<CustomListener>(new CustomListener());
>         }
>     
>         public static void main(String[] args) {
>             SpringApplication.run(DemoApplication.class, args);
>         }
>     }
> 
> **访问结果：do filter  
>                   servlet get method  
>                   servlet post method**
> 
>  
> 
>    (2)第二种方法： ServletContextInitializer 接口直接注册 需要的Servlet和Fileter和Listener
> 
>     package com.nyist.demo;
>     
>     
>     import com.nyist.demo.utils.filter.CustomFilter;
>     import com.nyist.demo.utils.listener.CustomListener;
>     import com.nyist.demo.utils.servlet.CustomServlet;
>     import org.springframework.boot.SpringApplication;
>     import org.springframework.boot.autoconfigure.SpringBootApplication;
>     import org.springframework.boot.web.servlet.ServletContextInitializer;
>     
>     import javax.servlet.DispatcherType;
>     import javax.servlet.ServletContext;
>     import javax.servlet.ServletException;
>     import java.util.EnumSet;
>     
>     
>     @SpringBootApplication
>     public class DemoApplication implements ServletContextInitializer {
>     
>             @Override  public void onStartup(ServletContext servletContext) throws ServletException {
>                 servletContext.addServlet("customServlet", new CustomServlet()).addMapping("/nyist");
>                 servletContext.addFilter("customFilter", new CustomFilter()).addMappingForServletNames(EnumSet.of(DispatcherType.REQUEST), true,"customServlet");
>                 servletContext.addListener(new CustomListener());
>             }
>     
>         public static void main(String[] args) {
>             SpringApplication.run(DemoApplication.class, args);
>         }
>     }
> 
>       (3)第三种方法：在 SpringBootApplication 上使用@ServletComponentScan 注解后，直接通过@WebServlet、@WebFilter、@WebListener 注解自动注册 
> 
>                   ![70][]
> 
>                   ![70 1][]
> 
>                  ![70 2][]
> 
>       ![70 3][]
> 
> **运行结果：**
> 
> **            contextInitialized  
>             init filter**
> 
> **            do filter  
>             servlet get method  
>             servlet post method**  
>

[70]: /images/20220505/76edcb6386ce448b958969b8b72e2ffc.png
[70 1]: /images/20220505/4882c12be57d4b8f85e67bd056fcc40c.png
[70 2]: /images/20220505/9688a662efdb400ab1ca7199a01ceb49.png
[70 3]: /images/20220505/7650603b633041dc90b75564122acc5c.png