如何用过滤器过滤HTTP协议和非HTTP协议编码

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在编写web时，最苦恼的事情就是乱码了。

一直没怎么考虑过JSP第一句话中

<%@ page language="java" contentType="text/html; charset=GBK"  pageEncoding="GBK"%>

的ContentType和pageEncoding具体是用做什么的，害自己做了过滤器也老是出现问题。

Google下：

contentType ------------指定的是JSP页最终 Browser(客户端)所见到的网页内容的编码.pageEncoding ------------指定JSP编写时所用的编码

如果害怕忘了在每个jsp都加上这样的编码，或者由于不同环境所需的客户端所见编码的不同。加上过滤器来解决

1.HTTP协议下的过滤：

（1.login.jsp ）用来模拟输入数据登录

<%@ page language="java"  pageEncoding="GBK"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" ><title>HTTP协议和URL编码</title></head><body><p>这里仅仅POST编码测试</p><form action="main.jsp" method="post"><label>测试HTTP协议</label><input type="text" name="infoPost" /><input type="submit" value="提交"> </form><hr><p>测试通过GET传送（url方式）</p><form action="main.jsp" method="get"><label>测试URL</label><input type="text" name="infoGet" /><input type="submit" value="提交"> </form></body></html>

（2.main.jsp ）用来模拟得到数据

<%@ page language="java"  pageEncoding="GBK"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" ><title>获取页面传过来的值</title></head><body> 获取通过HTTP协议传送过来的值 <%=request.getParameter("infoPost") %><hr>获取通过URL传送过来的值<%=request.getParameter("infoGet") %></body></html>

（3.web.xml）配置

<!-- 编码过滤器 --> <filter> <filter-name>EncodeFilter</filter-name> <filter-class>demo.filter.EncodeFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>GBK</param-value> </init-param> </filter> <filter-mapping> <filter-name>EncodeFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>

（4.EncodeFilter.java）过滤器类

package demo.filter;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** 字符编码 */public class EncodeFilter implements Filter {protected String encoding;protected FilterConfig filterConfig;public EncodeFilter() {this.encoding = null;this.filterConfig = null;}public void destroy() {filterConfig = null;encoding = null;}public void doFilter(ServletRequest request, ServletResponse response,FilterChain filterChain) throws IOException, ServletException {/* * 处理通过HTTP协议提交的数据 */HttpServletRequest hrequest = (HttpServletRequest) request;HttpServletResponse hresponse = (HttpServletResponse) response;// 这里省略前面两段，直接用request..setCharacterEncoding(encoding);效果是一样的，这里为了说明这个是通过HTTP// 协议提交System.out.println("编码格式" + encoding);hrequest.setCharacterEncoding(encoding);filterChain.doFilter(request, response);}/* * 过滤器初始化 */public void init(FilterConfig filterConfig) throws ServletException {this.filterConfig = filterConfig;encoding = filterConfig.getInitParameter("encoding");}}

结果：

post方式参数存放在请求数据包的消息体中。get方式参数存放在请求数据包的请求行的URI字段中，以？开始以param=value&&parame2=value2的形式附加在URI字段之后。而request.setCharacterEncoding(charset); 只对消息体中的数据起作用，对于URI字段中的参数不起作用。

可以继承扩展HttpServletRequestWrapper 增加过滤功能

添加一个MyEncodeFilter类

package demo.filter;import java.io.UnsupportedEncodingException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletRequestWrapper;public class MyEncodeFilter extends HttpServletRequestWrapper{private String encoding="GBK";public MyEncodeFilter(HttpServletRequest request) {super(request);}public MyEncodeFilter(HttpServletRequest request,String encoding) {super(request);this.encoding=encoding;}//新增加一个转码方法public String encodeName(String en){try {return new String(en.trim().getBytes("ISO-8859-1"),encoding);} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blockreturn en;}}//增强过滤的方法，就是将URI字段中的参数编码(重写)public String getParameter(String name) {//直接调用父类的getParameter方法获取参数的值String value=super.getParameter(name);//如果不为空就将其转码value=value==null?null:encodeName(value);return value;}}

改变后的Filter：

package demo.filter;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** 字符编码 */public class EncodeFilter  implements Filter {protected String encoding;protected FilterConfig filterConfig;public EncodeFilter() {this.encoding = null;this.filterConfig = null;}public void destroy() {filterConfig = null;encoding = null;}public void doFilter(ServletRequest request, ServletResponse response,FilterChain filterChain) throws IOException, ServletException {/* * 处理通过HTTP协议提交的数据 */HttpServletRequest hrequest = (HttpServletRequest) request;// 这里省略前面两段，直接用request..setCharacterEncoding(encoding);效果是一样的，这里为了说明这个是通过HTTP// 协议提交System.out.println("编码格式" + encoding);hrequest.setCharacterEncoding(encoding);//新增加方法<只要通过url来头中肯定有get>if(hrequest.getMethod().equalsIgnoreCase("get")){hrequest=new MyEncodeFilter(hrequest,encoding);} //filterChain.doFilter(hrequest, response);}/* * 过滤器初始化 */public void init(FilterConfig filterConfig) throws ServletException {this.filterConfig = filterConfig;encoding = filterConfig.getInitParameter("encoding");}}

解决成功！