request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;@WebFilter(filterName = "TestFilter2",urlPatterns = "/*")
public class TestFilter2 implements Filter {public void destroy() {}public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {chain.doFilter(req, resp);}public void init(FilterConfig config) throws ServletException {}}

chain.doFilter(req, resp);

 1 public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
 2         //这样在每个Servlet执行的时候都会先进行这个
 3         HttpServletRequest request = (HttpServletRequest) req;
 4         HttpServletResponse response = (HttpServletResponse) resp;
 5
 6         request.setCharacterEncoding("utf-8");
 7         response.setContentType("text/html;charset=utf-8");
 8
 9         //因为有可能不止这一个过滤器,所以需要将所有的过滤器执行
10         //注意 这一行代码一定要写到最后
11         chain.doFilter(req, resp);
12     }

 1 import javax.servlet.*;
 2 import javax.servlet.annotation.WebFilter;
 3 import javax.servlet.http.HttpServletRequest;
 4 import javax.servlet.http.HttpServletRequestWrapper;
 5 import javax.servlet.http.HttpServletResponse;
 6 import java.io.IOException;
 7 import java.io.UnsupportedEncodingException;
 8
 9 /**
10  * urlPatterns代表的是需要将那些路径进行过滤器过滤  这里为* 代表所有的路径都需要进入这个过滤器
11  */
12 @WebFilter(filterName = "TestFilter",urlPatterns = "/*")
13 public class TestFilter implements Filter {
14     public void destroy() {
15     }
16
17     /**
18      * 在这里面写的任何代码  在执行Servlet JSP 等前 都会被执行
19      */
20     public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
21         //这样在每个Servlet执行的时候都会先进行这个
22         HttpServletRequest request = (HttpServletRequest) req;
23         HttpServletResponse response = (HttpServletResponse) resp;
24
25         request.setCharacterEncoding("utf-8");
26         response.setContentType("text/html;charset=utf-8");
27
28         //因为有可能不止这一个过滤器,所以需要将所有的过滤器执行
29         //注意 这一行代码一定要写到最后
30         chain.doFilter(req, resp);
31     }
32
33     public void init(FilterConfig config) throws ServletException {
34
35     }
36
37     //通过重写getParameter方法,实现get方法自动转码
38     class MyWrapper extends HttpServletRequestWrapper{
39         private HttpServletRequest request;
40         public MyWrapper(HttpServletRequest request) {
41             super(request);
42             this.request = request;
43         }
44
45         @Override
46         public String getParameter(String name) {
47             String value = this.request.getParameter(name);
48             if(value == null){
49                 return null;
50             }
51
52             //如果是get方法提交过来的
53             if(this.request.getMethod().equalsIgnoreCase("get")){
54                 try {
55                     // 进行转码
56                     value = new String(value.getBytes("ISO-8859-1"),"utf-8");
57                 } catch (UnsupportedEncodingException e) {
58                     e.printStackTrace();
59                 }
60             }
61
62             //屏蔽尖括号 换成 > <
63             value = value.replace(">",">");
64             value = value.replace("<","&lt;");
65
66             return value;
67         }
68     }
69 }