1 说明
乱码问题：
- 获取请求参数中的乱码问题；
- POST请求：request.setCharacterEncoding(“utf-8”)；
- GET请求：new String(request.getParameter(“xxx”).getBytes(“iso-8859-1”), “utf-8”)；
- Tomcat 8.5.20、Tomcat 9.0.0.M26 默认编码都是utf-8,所有不出现GET请求乱码问题，所以不需处理
- 响应的乱码问题：response.setContextType(“text/html;charset=utf-8”)。
2、当GET请求出现乱码问题时（默认编码为ISO-8859-1时），可采用以下方法解决：
1 package web.filter;
2
3 import javax.servlet.*;
4 import javax.servlet.annotation.WebFilter;
5 import javax.servlet.http.HttpServletRequest;
6 import java.io.IOException;
7
8 @WebFilter(filterName = "EncodingFilter",urlPatterns = "/*")
9 public class EncodingFilter implements Filter {
10 public void destroy() { }
11 public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
12 //处理post请求编码问题
13 req.setCharacterEncoding("utf-8");
14
15 HttpServletRequest request = (HttpServletRequest) req;
16 //处理get请求的编码问题
17 if ( request.getMethod().equals("GET")){
18 EncodingRequest er = new EncodingRequest(request);
19 chain.doFilter(er, resp);
20 } else {
21 chain.doFilter(req,resp);
22 }
23 }
24 public void init(FilterConfig config) throws ServletException { }
25 }
1 package web.filter;
2
3 import javax.servlet.http.*;
4 import java.io.UnsupportedEncodingException;
5
6 /**
7 * 装饰request
8 */
9 public class EncodingRequest extends HttpServletRequestWrapper{
10 private HttpServletRequest request ;
11 public EncodingRequest(HttpServletRequest req) {
12 super(req);
13 this.request = req;
14 }
15 public String getParameter(String s) {
16 String value = request.getParameter("s");
17 //处理编码问题
18 try {
19 value = new String(value.getBytes("iso-8859-1"),"utf-8");
20 } catch (UnsupportedEncodingException e) {
21 throw new RuntimeException(e);
22 }
23 return value;
24 }
25 }
1 package web.servlet;
2
3 import javax.servlet.ServletException;
4 import javax.servlet.annotation.WebServlet;
5 import javax.servlet.http.HttpServlet;
6 import javax.servlet.http.HttpServletRequest;
7 import javax.servlet.http.HttpServletResponse;
8 import java.io.IOException;
9
10 @WebServlet(name = "AServlet",urlPatterns = "/AServlet")
11 public class AServlet extends HttpServlet {
12 protected void doPost(HttpServletRequest request, HttpServletResponse response)
13 throws ServletException, IOException {
14 response.setContentType("text/html;charset=utf-8");
15 String username = request.getParameter("username");
16 response.getWriter().println(username);
17 }
18
19 protected void doGet(HttpServletRequest request, HttpServletResponse response)
20 throws ServletException, IOException {
21 response.setContentType("text/html;charset=utf-8");
22 String username = request.getParameter("username");
23 response.getWriter().println(username);
24 }
25 }
1 <%@ page contentType="text/html;charset=UTF-8" language="java" %> 2 <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> 3 <html> 4 <head> 5 <title>$Title$</title> 6 </head> 7 <body> 8 <a href="<c:url value='/AServlet?username=张三'/>">点击这里</a> 9 <form action="<c:url value='/AServlet'/> " method="post"> 10 用户名：<input type="text" name="username" value="李四"/> 11 <input type="submit" value="提交"/> 12 </form> 13 </body> 14 </html>
3、当只有POST请求出现乱码问题时（服务器默认编码为UTF-8时），可采用以下方法解决：
1 @WebFilter(filterName = "EncodingFilter",urlPatterns = "/*")
2 public class EncodingFilter implements Filter {
3 public void destroy() { }
4 public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
5 //处理post请求编码问题
6 req.setCharacterEncoding("utf-8");
7 chain.doFilter(req,resp);
8 }
9 public void init(FilterConfig config) throws ServletException {}
10 }
1 @WebServlet(name = "AServlet",urlPatterns = "/AServlet")
2 public class AServlet extends HttpServlet {
3 protected void doPost(HttpServletRequest request, HttpServletResponse response)
4 throws ServletException, IOException {
5 response.setContentType("text/html;charset=utf-8");
6 String username = request.getParameter("username");
7 response.getWriter().println(username);
8 }
9
10 protected void doGet(HttpServletRequest request, HttpServletResponse response)
11 throws ServletException, IOException {
12 response.setContentType("text/html;charset=utf-8");
13 String username = request.getParameter("username");
14 response.getWriter().println(username);
15 }
16 }