四個有用的過濾器 Filter

一、使瀏覽器不緩存頁面的過濾器
import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
* 用於的使 Browser 不緩存頁面的過濾器
*/
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、檢測用戶是否登陸的過濾器

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;

/**
* 用於檢測用戶是否登陸的過濾器，如果未登錄，則重定向到指的登錄頁面


* 配置參數


* checkSessionKey 需檢查的在 Session 中保存的關鍵字

* redirectURL 如果用戶未登錄，則重定向到指定的頁面，URL不包括 ContextPath

* notCheckURLList 不做檢查的URL列表，以分號分開，並且 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());
    }
   }
}
}

三、字符編碼的過濾器

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

/**
* 用於設置 HTTP 請求字符編碼的過濾器，通過過濾器參數encoding指明使用何種字符編碼,用於處理Html Form請求參數的中文問題
*/
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、資源保護過濾器


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) {

              //處理用戶登錄
       /* UserBean user = (UserBean)req.getSession().getAttribute(BeanNames.USER_BEAN);

  if (user != null && user.getLoggedIn()) {
   //user logged in
   return true;
  }
  else {
   return false;
  }*/
 }
}