Java 五個有用的過濾器

時間 2019-12-11

標籤 java 五個有用過濾器欄目 Java 简体版

原文原文鏈接

五個有用的過濾器

1、使瀏覽器不緩存頁面的過濾器 html

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    
{    
}    
}

2、檢測用戶是否登錄的過濾器

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錄的過濾器，若是未登陸，則重定向到指的登陸頁面 


* 配置參數 


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

* redirectURL 若是用戶未登陸，則重定向到指定的頁面，URL不包括 ContextPath 

* notCheckURLList 不作檢查的URL列表，以分號分開，而且 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());    
     }    
    }    
}    
}

3、字符編碼的過濾器

java

import javax.servlet.*;    
import java.io.IOException;    
   
/** 
* 用於設置 HTTP 請求字符編碼的過濾器，經過過濾器參數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");    
   
}    
}

4、資源保護過濾器

web

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) {    
   
              //處理用戶登陸    
       /* 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限制用戶瀏覽權限

在一個系統中一般有多個權限的用戶。不一樣權限用戶的能夠瀏覽不一樣的頁面。使用Filter進行判斷不只省下了代碼量，並且若是要更改的話只須要在Filter文件裏動下就能夠。
如下是Filter文件代碼：

apache

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 {    
        // 獲取uri地址    
         HttpServletRequest request=(HttpServletRequest)sreq;    
         String uri = request.getRequestURI();    
         String ctx=request.getContextPath();    
         uri = uri.substring(ctx.length());    
        //判斷admin級別網頁的瀏覽權限    
        if(uri.startsWith("/admin")) {    
            if(request.getSession().getAttribute("admin")==null) {    
                 request.setAttribute("message","您沒有這個權限");    
                 request.getRequestDispatcher("/login.jsp").forward(sreq,sres);    
                return;    
             }    
         }    
        //判斷manage級別網頁的瀏覽權限    
        if(uri.startsWith("/manage")) {    
            //這裏省去    
             }    
         }    
        //下面還能夠添加其餘的用戶權限，省去。    
   
     }    
   
    public void init(FilterConfig arg0) throws ServletException {    
            
     }    
   
}

配置文件：

<!-- 判斷頁面的訪問權限 -->   
  <filter>   
     <filter-name>RightFilter</filter-name>   
      <filter-class>cn.itkui.filter.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>

在web.xml中加入Filter的配置，以下：瀏覽器

<filter>   

        <filter-name>EncodingAndCacheflush</filter-name>   
        <filter-class>EncodingAndCacheflush</filter-class>   
        <init-param>   
            <param-name>encoding</param-name>   
            <param-value>UTF-8</param-value>   
        </init-param>   
    </filter>   
    <filter-mapping>   
        <filter-name>EncodingAndCacheflush</filter-name>   
        <url-pattern>/*</url-pattern>   
    </filter-mapping>

要傳遞參數的時候最好使用form進行傳參，若是使用連接的話當中文字符的時候過濾器轉碼是不會起做用的，還有就是頁面上

form的method也要設置爲post，否則過濾器也起不了做用緩存