Filter

Filter：过滤器，用来过滤网站的数据，如处理中文乱码、登陆验证等。

1. 步骤

1. 编写一个类，实现Filter接口，并重写对应的方法。

   package com.gs.filter;
   
   import jakarta.servlet.*;
   import java.io.IOException;
   
   /**
    * @author admin
    */
   public class CharacterEncodingFilter implements Filter {
       @Override
       public void init(FilterConfig config) throws ServletException {
       }
   
       @Override
       public void destroy() {
       }
   
       @Override
       public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
           request.setCharacterEncoding("utf-8");
           response.setCharacterEncoding("utf-8");
           response.setContentType("text/html;charset=UTF-8");
           chain.doFilter(request, response);
       }
   }
   

2. 在web.xml中配置Filter

   <filter>
     <filter-name>CharacterEncodingFilter</filter-name>
     <filter-class>com.gs.filter.CharacterEncodingFilter</filter-class>
   </filter>
   
   <filter-mapping>
     <filter-name>CharacterEncodingFilter</filter-name>
     <url-pattern>/hello/*</url-pattern>
   </filter-mapping>