j2ee学习笔记 Filter过滤器

作用：过滤response和request对象的内容

使用：

　　Filter是J2EE的一个接口，自定义Filter需要实现该接口，并重写所有的方法.

　　Filter提供的方法：

     init()

　　doFilter()

　　destory()

在web.xml中的配置：

* 实现步骤:
* 创建Java类,实现Filter接口,并且重写所有方法.
* 在web.xml文件中进行配置.
<filter>
<filter-name>MyFilter1</filter-name>
<filter-class>filter.MyFilter1</filter-class>
</filter>
<filter-mapping>
<filter-name>MyFilter1</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

案例：使用filter解决中文乱码：

Myfilter.java

package 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;

//解决全站中文乱码
public class Myfilter1 implements Filter{

    @Override
    public void destroy() {      
    }
    @Override
    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {
        //进行Request和Response对象的类型强转
        HttpServletRequest request = (HttpServletRequest)req;
        HttpServletResponse response = (HttpServletResponse)res;
        //解决中文乱码问题1.请求的中文乱码Get 和 Post 2.响应中文乱码
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        //3.创建自定义的Request
        
        //4.放行
        chain.doFilter(request, response);        
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {  
    }

}

ServletTest.java

package filter;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletTest extends HttpServlet {
  
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
      
    }
    
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //获取表单信息
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        
        System.out.println(username + "--" + password);
        
        response.getWriter().println("中文doPost正常");
    
    }

}

web.xml配置文件

 <filter>
      <filter-name>Myfilter1</filter-name>
      <filter-class>filter.Myfilter1</filter-class>
  </filter>
  
    <filter-mapping>
      <filter-name>Myfilter1</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>

index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index.jsp' starting page</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    

  </head>
  
  <body>
//表单
    <form action="servlet/ServletTest" method="post">
        用户名：<input type="text" name="username"><br>
        密码：<input type="password" name="password"><br>
        <input type="submit" value="提交">
    </form>
  </body>
</html>

此处action的路径有三种写法：

1.相对路径："servlet/ServletTest" 

2.绝对路径："/Filter/servlet/ServletTest"

3.获取路径：${pageContext.request.contextPath }

 

posted @ 2016-11-30 18:12  kangjie  阅读(945)  评论(0)    收藏  举报