五个有用的过滤器

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jsp 过滤器

一、使浏览器不缓存页面的过滤器

package com.test;

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.HttpServletResponse;

/**
 * 用于的使Browser不缓存页面的过滤器
 */
public class ForceNoCacheFilter implements Filter {

	public void destroy() {

	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain filterChain) throws IOException, ServletException {
		((HttpServletResponse) response).setHeader("Cache-Control", "no-cache");
		((HttpServletResponse) response).setHeader("Pragma", "no-cache");
		((HttpServletResponse) response).setDateHeader("Expires", -1);
		filterChain.doFilter(request, response);
	}

	public void init(FilterConfig arg0) throws ServletException {

	}

}

二、检测用户是否登陆的过滤器

package com.test;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

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;

/**
 * 用于检测用户是否登陆的过滤器，如果未登录，则重定向到指的登录页面 
 * 配置参数 
 * checkSessionKey: 需检查的在Session中保存的关键字
 * redirectURL: 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath 
 * notCheckURLList: 不做检查的URL列表，以分号分开，并且URL中不包括 ContextPath
 */
@SuppressWarnings("unchecked")
public class CheckLoginFilter implements Filter {

	protected FilterConfig filterConfig = null;
	private String redirectURL = null;
	private List notCheckURLList = new ArrayList();
	private String sessionKey = null;

	public void destroy() {
		notCheckURLList.clear();
	}

	public void doFilter(ServletRequest servletRequest,
			ServletResponse servletResponse, FilterChain filterChain)
			throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) servletRequest;
		HttpServletResponse response = (HttpServletResponse) servletResponse;

		HttpSession session = request.getSession();
		if (sessionKey == null) {
			filterChain.doFilter(request, response);
			return;
		}
		if ((!checkRequestURIIntNotFilterList(request))
				&& session.getAttribute(sessionKey) == null) {
			response.sendRedirect(request.getContextPath() + redirectURL);
			return;
		}
		filterChain.doFilter(servletRequest, servletResponse);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		this.filterConfig = filterConfig;
		redirectURL = filterConfig.getInitParameter("redirectURL");
		sessionKey = filterConfig.getInitParameter("checkSessionKey");

		String notCheckURLListStr = filterConfig.getInitParameter("notCheckURLList");

		if (notCheckURLListStr != null) {
			StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";");
			notCheckURLList.clear();
			while (st.hasMoreTokens()) {
				notCheckURLList.add(st.nextToken());
			}
		}
	}

	private boolean checkRequestURIIntNotFilterList(HttpServletRequest request) {
		String uri = request.getServletPath()
				+ (request.getPathInfo() == null ? "" : request.getPathInfo());
		return notCheckURLList.contains(uri);
	}

}

三、字符编码的过滤器

package com.test;

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;

/**
 * 用于设置 HTTP 请求字符编码的过滤器，通过过滤器参数encoding指明使用何种字符编码,用于处理Html Form请求参数的中文问题
 * 只对post方式有效
 */
public class CharacterEncodingFilter implements Filter {

	protected FilterConfig filterConfig = null;
	protected String encoding = "";

	public void destroy() {
		filterConfig = null;
		encoding = null;
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		
		if (encoding != null) {
			request.setCharacterEncoding(encoding);
		}
		chain.doFilter(request, response);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		this.filterConfig = filterConfig;
		this.encoding = filterConfig.getInitParameter("encoding");
	}

}

四、资源保护过滤器

package com.test;

import java.io.IOException;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

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 org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

@SuppressWarnings("unchecked")
public class SecurityFilter implements Filter {

	private static final String LOGIN_PAGE_URI = "login.jsp";

	// the logger object
	private Log logger = LogFactory.getLog(this.getClass());

	// a set of restricted resources
	private Set restrictedResources;

	public void destroy() {

	}

	public void doFilter(ServletRequest req, ServletResponse res,
			FilterChain chain) throws IOException, ServletException {
		this.logger.debug("doFilter");

		String contextPath = ((HttpServletRequest) req).getContextPath();
		String requestUri = ((HttpServletRequest) req).getRequestURI();

		this.logger.debug("contextPath = " + contextPath);
		this.logger.debug("requestUri = " + requestUri);

		if (this.contains(requestUri, contextPath)
				&& !this.authorize((HttpServletRequest) req)) {
			this.logger.debug("authorization failed");
			((HttpServletRequest) req).getRequestDispatcher(LOGIN_PAGE_URI)
					.forward(req, res);
		} else {
			this.logger.debug("authorization succeeded");
			chain.doFilter(req, res);
		}
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		this.restrictedResources = new HashSet();
		this.restrictedResources.add("/createProduct.jsp");
		this.restrictedResources.add("/editProduct.jsp");
		this.restrictedResources.add("/productList.jsp");
	}

	private boolean contains(String value, String contextPath) {
		Iterator ite = this.restrictedResources.iterator();

		while (ite.hasNext()) {
			String restrictedResource = (String) ite.next();

			if ((contextPath + restrictedResource).equalsIgnoreCase(value)) {
				return true;
			}
		}

		return false;
	}

	private boolean authorize(HttpServletRequest req) {

		// 处理用户登录
//		UserBean user = (UserBean) req.getSession().getAttribute(
//				BeanNames.USER_BEAN);
//
//		if (user != null && user.getLoggedIn()) {
//			// user logged in
//			return true;
//		} else {
//			return false;
//		}
		return false;
	}
}

五、利用Filter限制用户浏览权限

package com.test;

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;

//在一个系统中通常有多个权限的用户。不同权限用户的可以浏览不同的页面。
//使用Filter进行判断不仅省下了代码量，而且如果要更改的话只需要在Filter文件里动下就可以。 
public class RightFilter implements Filter {

	public void destroy() {

	}

	public void doFilter(ServletRequest srequest, ServletResponse sresponse,
			FilterChain chain) throws IOException, ServletException {
		// 获取uri地址
		HttpServletRequest request = (HttpServletRequest) srequest;
		String uri = request.getRequestURI();
		String ctx = request.getContextPath();
		uri = uri.substring(ctx.length());
		
		// 判断admin级别网页的浏览权限
		if (uri.startsWith("/admin")) {
			if (request.getSession().getAttribute("admin") == null) {
				request.setAttribute("message", "您没有这个权限");
				request.getRequestDispatcher("/login.jsp").forward(srequest,
						sresponse);
				return;
			}
		}
		
		// 判断manage级别网页的浏览权限
		if (uri.startsWith("/manage")) {
			// 这里省去
		}
		// 下面还可以添加其他的用户权限，省去。
		chain.doFilter(srequest, sresponse);
	}

	public void init(FilterConfig filterConfig) throws ServletException {

	}

}

<?xml version="1.0" encoding="UTF-8"?>
        <filter>
		<filter-name>CharacterEncodingFilter</filter-name>
		<filter-class>com.test.CharacterEncodingFilter</filter-class>
		<init-param>
			<param-name>encoding</param-name>
			<param-value>UTF-8</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>CharacterEncodingFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
	
	<filter>   
     	<filter-name>RightFilter</filter-name>   
      	<filter-class>com.test.RightFilter</filter-class>   
  	</filter>   
	<filter-mapping>   
	    <filter-name>RightFilter</filter-name>   
	    <url-pattern>/admin/*</url-pattern>   
	</filter-mapping>   
  	<filter-mapping>   
      	<filter-name>RightFilter</filter-name>   
      	<url-pattern>/manage/*</url-pattern>   
  	</filter-mapping>

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