过滤器大全-JAVA91知识库

过滤器大全

转自:http://www.javaresearch.org/article/174920.htm 原作者：shiwenliang

　　一、字符编码的过滤器

　　二、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 {}
}

　　三、检测用户是否登陆的过滤器

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;
/** */
/** 
* 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 
*/
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());
            }
        }
    }
}

　　四、资源保护过滤器

package catalog.view.util;
import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
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;
/** */
/** 
* This Filter class handle the security of the application. 
* It should be configured inside the web.xml. 
* @author Derek Y. Shen 
*/
public class SecurityFilter implements Filter {
    //the login page uri 
    private static final String LOGIN_PAGE_URI = "login.jsf";
    //the logger object 
    private Log logger = LogFactory.getLog(this.getClass());
    //a set of restricted resources 
    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。以下是Filter文件代码：

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;
public class RightFilter implements Filter {
    public void destroy() {}
    public void doFilter(ServletRequest sreq, ServletResponse sres, FilterChain arg2) throws IOException,
    ServletException {
        // 获取uri地址 
        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 {
	}
}

< !--判断页面的访问权限--> RightFilter < /filter-name>

在web.xml中加入Filter的配置，如下：

　　要传递参数的时候最好使用form进行传参，如果使用链接的话当中文字符的时候过滤器转码是不会起作用的，还有就是页面上form的method也要设置为post，不然过滤器也起不了作用。