五个有用的过滤器

【五个有用的过滤器】

 

一、使浏览器不缓存页面的过滤器

import javax.servlet.*;    
import javax.servlet.http.HttpServletResponse;    
import java.io.IOException;    
/** 
* 用于的使 Browser 不缓存页面的过滤器 
*/   
public class ForceNoCacheFilter implements Filter {  
	  
   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 destroy() { }    
   
	public void init(FilterConfig filterConfig) throws ServletException { }    
}    

  二、检测用户是否登陆的过滤器

/** 
 * 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 
 */
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.util.List;
import java.util.ArrayList;
import java.util.StringTokenizer;
import java.io.IOException;

public class CheckLoginFilter implements Filter {
	protected FilterConfig filterConfig = null;
	private String redirectURL = null;
	private List notCheckURLList = new ArrayList();
	private String sessionKey = null;

	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 destroy() {
		notCheckURLList.clear();
	}

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

	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());
			}
		}
	}
}

  

三、字符编码的过滤器

 

/**
 * 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
 */
import javax.servlet.*;
import java.io.IOException;

public class CharacterEncodingFilter implements Filter {
	protected FilterConfig filterConfig = null;
	protected String encoding = "";

	public void doFilter(ServletRequest servletRequest,
			ServletResponse servletResponse, FilterChain filterChain)
			throws IOException, ServletException {
		if (encoding != null)
			servletRequest.setCharacterEncoding(encoding);
		filterChain.doFilter(servletRequest, servletResponse);
	}

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

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

 四、资源保护过滤器

/**
 * This Filter class handle the security of the application.
 * 
 * It should be configured inside the web.xml.
 * 
 * @author Derek Y. Shen
 */
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
import java.util.Iterator;
import java.util.Set;
import java.util.HashSet;     
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class SecurityFilter implements Filter {
	private static final String LOGIN_PAGE_URI = "login.jsf";
	private Log logger = LogFactory.getLog(this.getClass());
	private Set restrictedResources;
	/**
	 * Initializes the Filter.
	 */
	public void init(FilterConfig filterConfig) throws ServletException {
		this.restrictedResources = new HashSet();
		this.restrictedResources.add("/createProduct.jsf");
		this.restrictedResources.add("/editProduct.jsf");
		this.restrictedResources.add("/productList.jsf");
	}
	/**
	 * Standard doFilter object.
	 */
	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 destroy() {}

	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; }
		 */
	}
}

 

五 利用Filter限制用户浏览权限

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。

import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;

public class RightFilter implements Filter {

	public void destroy() {}

	public void doFilter(ServletRequest sreq, ServletResponse sres,
			FilterChain arg2) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) sreq;
		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(sreq, sres);
				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。

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