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编码转换过滤器

------------------siwuxie095

   

   

   

   

   

   

   

   

   

使用过滤器进行编码转换

   

Java Web 开发中,经常会遇到乱码的问题,统一字符编码是

解决乱码问题的非常有效的手段

   

   

   

一个简单的编码转换过滤器实例:

   

使用过滤器对请求中的参数信息进行编码转换

   

   

   

工程结构目录如下:

   

技术分享

   

   

   

   

后端代码:

   

LoginServlet.java:

   

package com.siwuxie095.servlet;

   

import java.io.IOException;

   

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

   

// LoginServlet 继承自 HttpServlet

public class LoginServlet extends HttpServlet {

/**

* 用于序列化和反序列化的 ID

*/

private static final long serialVersionUID = -7740192486028671728L;

   

 

//覆盖父类 HttpServlet doGet() 方法

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

System.out.println("===== doGet =====");

// doGet() 方法里调用 doPost() 方法

//这样,GET请求和POST请求可以共用一套处理逻辑

doPost(req, resp);

}

   

//覆盖父类 HttpServlet doPost() 方法

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

System.out.println("===== doPost =====");

String userName=req.getParameter("uname");

String password=req.getParameter("upwd");

 

System.out.println("用户名:"+userName);

System.out.println("密码:"+password);

 

String forward=null;

 

if (userName.equals("李白")&&password.equals("8888")) {

forward="/success.jsp";

}else {

forward="/error.jsp";

}

 

RequestDispatcher rd=req.getRequestDispatcher(forward);

rd.forward(req, resp);

}

 

}

   

   

   

EncodingFilter.java:

   

package com.siwuxie095.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;

   

   

public class EncodingFilter implements Filter {

   

//声明一个成员变量 用来保存当前应用的字符集名称

private String charEncoding=null;

 

 

public EncodingFilter() {

 

}

   

 

public void init(FilterConfig fConfig) throws ServletException {

//在部署描述符中设置该应用的默认字符编码集 init方法中获取到该设置

charEncoding=fConfig.getInitParameter("encoding");

//如果字符编码的名称没有设置 就抛出一个异常

if (charEncoding==null) {

throw new ServletException("EncodingFilter中的编码设置为空!!!");

}

}

   

 

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

//如果当前应用的默认编码,与请求中的编码值不一致

if (!charEncoding.equals(request.getCharacterEncoding())) {

//那么就将请求中的编码设置成当前默认的编码设置

request.setCharacterEncoding(charEncoding);

}

 

//将响应的编码设置也改成当前默认的编码设置

response.setCharacterEncoding(charEncoding);

chain.doFilter(request, response);

}

 

 

public void destroy() {

 

}

 

}

   

   

   

前端代码:

   

login.jsp:

   

<%@ page language="java" contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

<!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" content="text/html; charset=UTF-8">

<title>登录页面</title>

   

<script type="text/javascript">

function check(form){

if(document.forms.loginForm.uname.value=http://www.mamicode.com/=""){

alert("请输入用户名!");

document.forms.loginForm.uname.focus();

return false;

}

if(document.forms.loginForm.upwd.value=http://www.mamicode.com/=""){

alert("请输入密码!");

document.forms.loginForm.upwd.focus();

return false;

}

}

</script>

   

<style type="text/css">

body {

color: #000; font-size =14px;

margin: 20px, auto;

}

</style>

   

</head>

<body>

   

<!-- 添加表单,url在部署描述符中进行配置,使用post方式来提交 -->

<form action="<%= request.getContextPath() %>/loginServlet" method="post" name="loginForm">

<table border="1" cellspacing="0" cellpadding="5" bordercolor="silver" align="center">

<tr>

<td colspan="2" align="center" bgcolor="#E8E8E8">用户登录</td>

</tr>

<tr>

<td>用户名:</td>

<td><input type="text" name="uname" /></td>

</tr>

<tr>

<td>密码:</td>

<td><input type="password" name="upwd" /></td>

</tr>

<tr>

<td colspan="2" align="center">

<input type="submit" name="submit" onclick="return check(this);" />

<input type="reset" name="reset" />

</td>

</tr>

</table>

</form>

   

</body>

</html>

   

   

   

success.jsp:

   

<%@ page language="java" contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

<!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" content="text/html; charset=UTF-8">

<title>登录成功提示页面</title>

   

<style type="text/css">

body {

color: #000; font-size =14px;

margin: 20px, auto;

}

   

#message {

text-align: center;

}

</style>

   

</head>

<body>

   

<div id="message">

登录成功!<br/>

您提交的信息为:<br/>

用户名:<%= request.getParameter("uname") %><br/>

密码:<%= request.getParameter("upwd") %><br/>

<a href="<%= request.getContextPath() %>/login.jsp">返回登录页面</a>

</div>

   

</body>

</html>

   

   

   

error.jsp:

   

<%@ page language="java" contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

<!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" content="text/html; charset=UTF-8">

<title>登录失败提示页面</title>

   

<style type="text/css">

body {

color: #000; font-size =14px;

margin: 20px, auto;

}

   

#message {

text-align: center;

}

</style>

   

</head>

<body>

   

<div id="message">

登录失败!<br/>

您提交的信息为:<br/>

用户名:<%= request.getParameter("uname") %><br/>

密码:<%= request.getParameter("upwd") %><br/>

<a href="<%= request.getContextPath() %>/login.jsp">返回登录页面</a>

</div>

   

</body>

</html>

   

   

   

在部署描述符 web.xml 中注册 servlet 和 filter:

   

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1">

<display-name>MyFilter</display-name>

<welcome-file-list>

<welcome-file>index.html</welcome-file>

<welcome-file>index.htm</welcome-file>

<welcome-file>index.jsp</welcome-file>

<welcome-file>default.html</welcome-file>

<welcome-file>default.htm</welcome-file>

<welcome-file>default.jsp</welcome-file>

</welcome-file-list>

 

<servlet>

<servlet-name>LoginServlet</servlet-name>

<servlet-class>com.siwuxie095.servlet.LoginServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>LoginServlet</servlet-name>

<url-pattern>/loginServlet</url-pattern>

</servlet-mapping>

 

<filter>

<filter-name>EncodingFilter</filter-name>

<filter-class>com.siwuxie095.filter.EncodingFilter</filter-class>

<init-param>

<param-name>encoding</param-name>

<param-value>UTF-8</param-value>

</init-param>

</filter>

<filter-mapping>

<filter-name>EncodingFilter</filter-name>

<url-pattern>/*</url-pattern>

</filter-mapping>

 

 

</web-app>

   

   

部署描述符 web.xml 在 WEB-INF 目录下,如果没有,手动创建即可

   

选择工程 MyFilter,右键->Java EE Tools->Generate Deployment Descriptor Stub

   

   

   

访问:localhost:8080/MyFilter/login.jsp,分别输入 李白 和 8888

   

技术分享

   

   

   

跳转到:localhost:8080/MyFilter/loginServlet,登录成功

   

技术分享

   

   

   

如果没有 编码转换过滤器,则会乱码,且登录失败

   

技术分享

   

   

   

   

   

【made by siwuxie095】

编码转换过滤器