JAVAWeb开发之Servlet-19.Filter
2012-03-31 10:04
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JAVAWeb开发之Servlet-19.Filter
–Filter 简介–创建Filter的步骤
–获得Filter的初始化参数
–Filter 实例
?字符编码 Filter
?权限验证 Filter
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? Filter 简介
–Filter位于客户端和请求资源之间，在此起到过滤作用
–请求资源可以是，Servlet、JSP页面、HTML页面等
–他们在请求资源的前后来执行
–请求和响应通过Filter可以被修改
–Filter 常用在如下几个方面：
? Session 管理
? 权限验证
? 日志记录
? 字符编码转换
Filter 简介图示
? 创建Filter的步骤
– Filter 接口
? init 方法
public void init(FilterConfig filterConfig) throws ServletException
? doFilter 方法
public void doFilter(ServletRequest request,
ServletResponse response,
FilterChain chain)
throws java.io.IOException,
ServletException
? Destroy 方法
public void destroy()
– 创建Filter步骤
? 创建一个类实现Filter接口
– 方法: doFilter, init, destroy
?在doFilter方法中处理逻辑
– 参数: ServletRequest, ServletResponse, FilterChain
? FilterChain 调用doFilter方法
– 调用下一个过滤器或实际资源
? 注册filter，来过滤Servlet 和Jsp
–在web.xml中，使用 filter 和 filter-mapping
简单的Filter实例
调用WebRoot下面的testFilter.html测试Filter起作用了没？
Filter没有执行哈~
再次测试admin下的testFilter有没起作用？
pass herer~~~~~~在控制台打印出来了,但是页面没有显示Test Filter 1,证明被Filter拦截了。下面我们过滤链调用doFilter方法。
再次执行页面。
页面显示了Test Filter 1了
结构与Servlet相似。
MyFilter.java
package com.michael.servlet;
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 MyFilterimplements Filter {
public void destroy() {
}
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain chain) throws IOException, ServletException {
System.out.println("pass here~~~~~~~~");
chain.doFilter(arg0, arg1);
}
public void init(FilterConfig arg0)throws ServletException {
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<filter>
<filter-name>MyFilter</filter-name>
<filter-class>com.michael.servlet.MyFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>MyFilter</filter-name>
<url-pattern>/admin/*</url-pattern>
</filter-mapping>
</web-app>
testFilter.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>testFilter.html</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
</head>
<body>
<h1>Test Filter 1</h1>
</body>
</html>
? 获得Filter的初始化参数
–在web.xml配置文件的Filter声明中配置初始化参数
–在Filter实现类中获得初始化参数
? Filter 实例
–字符编码 Filter
测试一下提交的中文是否乱码？
用户名显示为乱码
下面我们将整个页面设置统一编码，用Filter来解决哈~
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<filter>
<filter-name>MyFilter</filter-name>
<filter-class>com.michael.servlet.MyFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>gbk</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>MyFilter</filter-name>
<url-pattern>/admin/*</url-pattern>
</filter-mapping>
<filter>
<filter-name>EncodingFilter</filter-name>
<filter-class>com.michael.servlet.EncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>EncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>RegisterServlet</servlet-name>
<servlet-class>com.michael.servlet.RegisterServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RegisterServlet</servlet-name>
<url-pattern>/servlet/RegisterServlet</url-pattern>
</servlet-mapping>
</web-app>
register.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>register.html</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
</head>
<body>
<form name="f1" id="f1" action="/Servlet_Filter/servlet/RegisterServlet" method="post">
<table border="0">
<tr>
<td>Username:</td>
<td><input type="text" name="username" id="login"></td>
</tr>
<tr>
<td>Password:</td>
<td><input type="password" name="password" id="password"></td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" value="Register"></td>
</tr>
</table>
</form>
</body>
</html>
RegisterServlet.java
package com.michael.servlet;
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 RegisterServletextends HttpServlet {
/**
* Constructor of the object.
*/
public RegisterServlet() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy();
// Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request,response);
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out
.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.print(username);
out.print(password);
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init()throws ServletException {
// Put your code here
}
}
EncodingFilter.java
package com.michael.servlet;
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 EncodingFilterimplements Filter{
public void destroy() {
// TODO Auto-generated method stub
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
request.setCharacterEncoding("gbk");
response.setCharacterEncoding("gbk");
chain.doFilter(request, response);
}
public void init(FilterConfig arg0)throws ServletException {
// TODO Auto-generated method stub
}
}
可以正常显示中文了哈~
–权限验证 Filter
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<filter>
<filter-name>MyFilter</filter-name>
<filter-class>com.michael.servlet.MyFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>gbk</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>MyFilter</filter-name>
<url-pattern>/admin/*</url-pattern>
</filter-mapping>
<filter>
<filter-name>EncodingFilter</filter-name>
<filter-class>com.michael.servlet.EncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>EncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<filter>
<filter-name>SessionFilter</filter-name>
<filter-class>com.michael.servlet.SessionFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>SessionFilter</filter-name>
<url-pattern>/admin/*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>RegisterServlet</servlet-name>
<servlet-class>com.michael.servlet.RegisterServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>com.michael.servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RegisterServlet</servlet-name>
<url-pattern>/servlet/RegisterServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/servlet/LoginServlet</url-pattern>
</servlet-mapping>
</web-app>
login.jsp
<%@ page language="java"import="java.util.*" pageEncoding="gbk"%>
<%
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 'login.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">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
${Login_Error }
<form name="f1" id="f1" action="/Servlet_Filter/servlet/LoginServlet" method="post">
<table border="0">
<tr>
<td>Username:</td>
<td><input type="text" name="username" id="login"></td>
</tr>
<tr>
<td>Password:</td>
<td><input type="password" name="password" id="password"></td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" value="Login"></td>
</tr>
</table>
</form>
</body>
</html>
LoginServlet.java
package com.michael.servlet;
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;
import javax.servlet.http.HttpSession;
public class LoginServletextends HttpServlet {
/**
* Constructor of the object.
*/
public LoginServlet() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy();
// Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request,response);
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession();
session.setAttribute("UserSession","user");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out
.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.print(" Welcome you! ");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init()throws ServletException {
// Put your code here
}
}
SessionFilter.java
package com.michael.servlet;
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;
import javax.servlet.http.HttpSession;
public class SessionFilterimplements Filter {
public void destroy() {
// TODO Auto-generated method stub
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest hrequest = (HttpServletRequest)request;
HttpServletResponse hresponse = (HttpServletResponse)response;
HttpSession session = hrequest.getSession();
String session_Value = (String)session.getAttribute("UserSession");
if(session_Value!=null&&session_Value.length()>=0){
chain.doFilter(request, response);
}else{
hrequest.setAttribute("Login_Error","请登录");
hrequest.getRequestDispatcher("/login.jsp").forward(hrequest, hresponse);
}
}
public void init(FilterConfig arg0)throws ServletException {
// TODO Auto-generated method stub
}
}
没有登录的状态下直接访问admin目录下的testFilter.thml页面，页面显示“请登录”。
下面我们输入用户名和密码进行模拟登录验证。
页面显示登录成功！
登录成功后我们再访问admin目录下的页面就可以正常访问了哈~
#################################################
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