检验用户名、密码、字符编码、页面缓存----Filter的基本使用 -

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检验用户名、密码、字符编码、页面缓存----Filter的基本使用

博客分类：

Filter

Servlet Java JSP Tomcat 浏览器


<%@ 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>Insert title here</title>
</head>
<body>

	<font color="red">${requestScope.errormsg }</font>
	<br><br>

	<form action="hello.jsp" method="post">
		Name: <input type="text" name="name"/><br><br>
		Password: <input type="password" name="password"/><br><br>
		<input type="submit" value="Submit"/>
	</form>

</body>
</html>

hello.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>Insert title here</title>
</head>
<body>

	<h4>Hello Page</h4><br><br>
	
	<%
		//request.setCharacterEncoding("UTF-8") ;
	%>
	
	hello : ${param.name }<br><br>
	
</body>
</html>

EncodingFilter.java


package com.syh.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * 字符编码过滤器,在设置这个过滤器的时候，还要将Tomcat的一个配置改变:
 * 修改 Tomcat 服务器的 conf 目录下的 server.xml 文件中的  <Connector> 为(67 行)
		<Connector port="8989" protocol="HTTP/1.1" 
		  connectionTimeout="20000" 
		redirectPort="8443" useBodyEncodingForURI="true" />,再次重新启动Tomcat服务器
 * @author Administrator
 *
 */

public class EncodingFilter implements Filter {

	private FilterConfig config ;
	
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		this.config = filterConfig ;
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		
		//1. 获取 ServletContext 对象
		ServletContext servletContext = config.getServletContext() ;
		
		//2. 获取 encoding 的初始化参数
		String encoding = servletContext.getInitParameter("encoding") ;
		
		//3. 设置 request 的字符编码
		request.setCharacterEncoding(encoding) ;
		
		chain.doFilter(request, response) ;
		
	}

	@Override
	public void destroy() {

	}

}

NoCacheFilter.java


package com.syh.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;

/**
 * 使浏览器不缓存页面的过滤器
 * @author Administrator
 *
 */

public class NoCacheFilter implements Filter {

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {

	}

	@Override
	public void doFilter(ServletRequest req, ServletResponse resp,
			FilterChain chain) throws IOException, ServletException {
		HttpServletResponse response = (HttpServletResponse) resp ;
		
		// 并不是所有的浏览器都能完全支持上面的三个响应头, 因此最好是同时使用下面的三个响应头
		response.setDateHeader("Expires",-1);
		response.setHeader("Cache-Control","no-cache");
		response.setHeader("Pragma","no-cache");
		
		chain.doFilter(req, resp) ;
		
	}

	@Override
	public void destroy() {

	}

}

NameFilter.java


package com.syh.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;

/**
 * 用户名检验过滤器
 * @author Administrator
 *
 */

public class NameFilter implements Filter {

	private FilterConfig config ;
	
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		this.config = filterConfig ;
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		
		//1. 获取表单中 name 的参数
		String paramName = request.getParameter("name") ;
		
		//2. 获取当前 Filter 中 name 的参数
		String initName = config.getInitParameter("name") ;
		
		//3. 比较
		if(paramName != null && initName.equals(paramName)) {
			//3.1  匹配，放行
			chain.doFilter(request, response) ;
		}else {
			
			//3.2 不匹配, 将页面转发到 /login.jsp, 并提示用户 "您输入的用户名不同"
			request.setAttribute("errormsg", "您输入的用户名" + paramName + "不同") ;
			request.getRequestDispatcher("/login.jsp").forward(request,response) ;
		}
		
		
	}

	@Override
	public void destroy() {

	}

}

PasswordFilter.java


package com.syh.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;

/**
 * 密码检验过滤器
 * @author Administrator
 *
 */

public class PasswordFilter implements Filter {

	private FilterConfig config ;
	
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		this.config = filterConfig ;
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		
		//1.获取表单中 password 的参数
		String paramPassword = request.getParameter("password") ;
		
		
		//2. 获取当前 Filter 的 password 的参数
		String initPassword = config.getInitParameter("password") ;
		
		//3. 比较
		if(paramPassword != null && initPassword.equals(paramPassword)) {
			//3.1 匹配， 放行
			chain.doFilter(request, response) ;
		} else {
			
			//3.2 不匹配, 将页面转发到 /login.jsp, 并提示用户 "您输入的密码不正确"
			request.setAttribute("errormsg", "您输入的密码不正确") ;
			request.getRequestDispatcher("/login.jsp").forward(request, response) ;
		}
	}

	@Override
	public void destroy() {

	}

}


<!-- 字符编码的参数 -->

	<context-param>
		<param-name>encoding</param-name>
		<param-value>UTF-8</param-value>
	</context-param>

	<!-- 字符编码的检验 -->

	<filter>
		<filter-name>EncodingFilter</filter-name>
		<filter-class>com.syh.filter.EncodingFilter</filter-class>
	</filter>

	<filter-mapping>
		<filter-name>EncodingFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

	<!-- 浏览器缓存的检验 -->

	<filter>
		<filter-name>NoCacheFilter</filter-name>
		<filter-class>com.syh.filter.NoCacheFilter</filter-class>
	</filter>

	<filter-mapping>
		<filter-name>NoCacheFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

	<!-- 用户名的检验 -->
	<filter>
		<filter-name>NameFilter</filter-name>
		<filter-class>com.syh.filter.NameFilter</filter-class>
		<init-param>
			<param-name>name</param-name>
			<param-value>Tom</param-value>
		</init-param>
	</filter>

	<filter-mapping>
		<filter-name>NameFilter</filter-name>
		<url-pattern>/hello.jsp</url-pattern>
	</filter-mapping>

	<!-- 用户名的检验 -->

	<filter>
		<filter-name>PasswordFilter</filter-name>
		<filter-class>com.syh.filter.PasswordFilter</filter-class>
		<init-param>
			<param-name>password</param-name>
			<param-value>1234</param-value>
		</init-param>
	</filter>

	<filter-mapping>
		<filter-name>PasswordFilter</filter-name>
		<url-pattern>/hello.jsp</url-pattern>
	</filter-mapping>