Filter

 1 public class CharacterEncodingFilter implements Filter {
 2 
 3     // 初始化
 4     public void init(FilterConfig filterConfig) throws ServletException {
 5         // web服务器启动的时候就初始化，随时等待过滤对象出现
 6         System.out.println("CharacterEncodingFilter初始化");
 7 
 8     }
 9 
10     public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
11 
12         /*
13         * filterChain
14         * 1：过滤器中的所有代码，在过滤特点的请求的时候都会执行
15         * 2：必须要让过滤器继续执行
16         * filterChain.doFilter(servletRequest, servletResponse);
17          *
18         *
19         * */
20 
21         // 处理乱码
22         request.setCharacterEncoding("utf-8");
23         response.setCharacterEncoding("utf-8");
24          response.setContentType("text/html;charset=UTF-8");
25 
26         System.out.println("执行前");
27         chain.doFilter(request, response); // 让请求继续走，如果不写程序到这里就被拦截停止，相当于中间商转移req和resp
28         System.out.println("执行后");
29     }
30 
31     // 销毁:web服务器关闭的时候才会销毁
32     public void destroy() {
33         System.out.println("CharacterEncodingFilter销毁");
34     }
35 }

1 <filter>
2         <filter-name>CharacterEncodingFilter</filter-name>
3         <filter-class>com.kuang.filter.CharacterEncodingFilter</filter-class>
4     </filter>
5     <filter-mapping>
6         <filter-name>CharacterEncodingFilter</filter-name>
7         <!--  只要是servlet下面的任何请求都走过滤器      -->
8         <url-pattern>/servlet/*</url-pattern>
9     </filter-mapping>