为什么在filter 中设置编码
之前每个servlet都设置编码方式，防止请求和响应出现乱码，那么出现大量重复代码，而filter能够对请求消息和响应消息进行处理，所以把重复代码提取到filter中来。
编写form.jsp
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8" import="java.util.*"%>
<!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">
</head>
<center>
<h3>用户登录</h3>
</center>
<body style="text-align: center;">
<a href="<%=request.getContextPath()%>/CharacterServlet?name=传智播客&password=123456">单击超链接登录</a>
<form action="<%=request.getContextPath()%>/CharacterServlet"
method="post">
<table border="1" width="600px" cellpadding="0" cellspacing="0"
align="center">
<tr>
<td height="30" align="center">用户名：</td>
<td> <input type="text" name="name" />
</td>
</tr>
<tr>
<td height="30" align="center">密 码：</td>
<td> <input type="password" name="password" />
</td>
</tr>
<tr>
<td height="30" colspan="2" align="center">
<input type="submit" value="登录" />
<input type="reset" value="重置" />
</td>
</tr>
</table>
</form>
</body>创建CharacterServlet
public class CharacterServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println(request.getParameter("name"));
System.out.println(request.getParameter("password"));
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}创建CharacterFilter
public class CharacterFilter implements Filter {
public void init(FilterConfig filterConfig) throws ServletException {
}
public void doFilter(ServletRequest req, ServletResponse resp,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
// 拦截所有的请求 解决全站中文乱码
// 指定 request 和 response 的编码
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
chain.doFilter(request, response);
}
public void destroy() {
}
}配置映射信息
<filter>
<filter-name>CharacterFilter</filter-name>
<filter-class>cn.itcast.chapter08.filter.CharacterFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CharacterFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>启动项目，测试结果
http://localhost:8080/chapter08/form.jsp
