过滤器的功能：过滤用户请求
Filter的创建：
第一步：创建一个类，实现Filter接口
第二步：调用他的init方法（初始化变量用的 服务器加载的时候就加载了），调用他的doFilter方法（里面的内容是你的Filter类要实现的功能），调用他的destroy方法（销毁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 CharsetEncodeFilter implements Filter { public void destroy() { System.out.println("CharsetEncodeFilter.destroy()"); } public void doFilter(ServletRequest Request, ServletResponse Response, FilterChain chain) throws IOException, ServletException { Response.setContentType("text/html; charset=utf-8");//作用是指定对服务器响应进行重新编码的编码。 Request.setCharacterEncoding("utf-8");//作用是设置对客户端请求进行重新编码的编码 chain.doFilter(Request, Response); } public void init(FilterConfig arg0) throws ServletException { System.out.println("CharsetEncodeFilter.init()"); } }
第三步：在xml文件中配置它的Filter类
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<filter>
<filter-name>CharsetEncodeFilter</filter-name>
<filter-class>com.servlet.CharsetEncodeFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CharsetEncodeFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
第四步 ：测试你的Filter功能是否正常
测试的jsp内容：
<%@ 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=ISO-8859-1"> <title>Insert title here</title> </head> <body> <form action="/Shopping/login" method="POST"> <input name="name" placeholder="用户名">用户名</input> <input name="password" type="password" placeholder="密码">密 码</input> <input type="submit"value="登录"></input> </form> </body> </html>
测试的java代码：（浏览器默认的编码格式是iso—8859-1，与java输出的编码格式不匹配，所以会造成乱码，但是上面我们进行了Filter编码所以，如果没有出现乱码，就表示我们的Filter应用成功）
import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; @WebServlet("/login") public class LoginServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void service(HttpServletRequest Request, HttpServletResponse Response) throws ServletException, IOException { String name =Request.getParameter("name"); String password=Request.getParameter("password"); PrintWriter writer = Response.getWriter(); writer.write(name+password); } }