几个有用的过滤器

四个有用的过滤器 Filter
关键字: servlet
java 代码
1.一、使浏览器不缓存页面的过滤器    
2.import javax.servlet.*;   
3.import javax.servlet.http.HttpServletResponse;   
4.import java.io.IOException;   
5.  
6./**  
7.* 用于的使 Browser 不缓存页面的过滤器  
8.*/  
9.public class ForceNoCacheFilter implements Filter {   
10.  
11.public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException   
12.{   
13.   ((HttpServletResponse) response).setHeader("Cache-Control","no-cache");   
14.   ((HttpServletResponse) response).setHeader("Pragma","no-cache");   
15.   ((HttpServletResponse) response).setDateHeader ("Expires", -1);   
16.   filterChain.doFilter(request, response);   
17.}   
18.  
19.public void destroy()   
20.{   
21.}   
22.  
23.     public void init(FilterConfig filterConfig) throws ServletException   
24.{   
25.}   
26.}   
27.  
28.二、检测用户是否登陆的过滤器   
29.  
30.import javax.servlet.*;   
31.import javax.servlet.http.HttpServletRequest;   
32.import javax.servlet.http.HttpServletResponse;   
33.import javax.servlet.http.HttpSession;   
34.import java.util.List;   
35.import java.util.ArrayList;   
36.import java.util.StringTokenizer;   
37.import java.io.IOException;   
38.  
39./**  
40.* 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   
41.1.1.* 配置参数   
2.1.1.* checkSessionKey 需检查的在 Session 中保存的关键字  
2.1.* redirectURL 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath  
2.1.* notCheckURLList 不做检查的URL列表，以分号分开，并且 URL 中不包括 ContextPath  
2.1.*/  
2.public class CheckLoginFilter   
3.implements Filter   
4.{   
5.     protected FilterConfig filterConfig = null;   
6.     private String redirectURL = null;   
7.     private List notCheckURLList = new ArrayList();   
8.     private String sessionKey = null;   
9.  
10.public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException   
11.{   
12.   HttpServletRequest request = (HttpServletRequest) servletRequest;   
13.   HttpServletResponse response = (HttpServletResponse) servletResponse;   
14.  
15.    HttpSession session = request.getSession();   
16.   if(sessionKey == null)   
17.   {   
18.    filterChain.doFilter(request, response);   
19.    return;   
20.   }   
21.   if((!checkRequestURIIntNotFilterList(request)) && session.getAttribute(sessionKey) == null)   
22.   {   
23.    response.sendRedirect(request.getContextPath() + redirectURL);   
24.    return;   
25.   }   
26.   filterChain.doFilter(servletRequest, servletResponse);   
27.}   
28.  
29.public void destroy()   
30.{   
31.   notCheckURLList.clear();   
32.}   
33.  
34.private boolean checkRequestURIIntNotFilterList(HttpServletRequest request)   
35.{   
36.   String uri = request.getServletPath() + (request.getPathInfo() == null ? "" : request.getPathInfo());   
37.   return notCheckURLList.contains(uri);   
38.}   
39.  
40.public void init(FilterConfig filterConfig) throws ServletException   
41.{   
42.   this.filterConfig = filterConfig;   
43.   redirectURL = filterConfig.getInitParameter("redirectURL");   
44.   sessionKey = filterConfig.getInitParameter("checkSessionKey");   
45.  
46.   String notCheckURLListStr = filterConfig.getInitParameter("notCheckURLList");   
47.  
48.   if(notCheckURLListStr != null)   
49.   {   
50.    StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";");   
51.    notCheckURLList.clear();   
52.    while(st.hasMoreTokens())   
53.    {   
54.     notCheckURLList.add(st.nextToken());   
55.    }   
56.   }   
57.}   
58.}   
59.  
60.三、字符编码的过滤器   
61.  
62.import javax.servlet.*;   
63.import java.io.IOException;   
64.  
65./**  
66.* 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  
67.*/  
68.public class CharacterEncodingFilter   
69.implements Filter   
70.{   
71.protected FilterConfig filterConfig = null;   
72.protected String encoding = "";   
73.  
74.public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException   
75.{   
76.         if(encoding != null)   
77.          servletRequest.setCharacterEncoding(encoding);   
78.         filterChain.doFilter(servletRequest, servletResponse);   
79.}   
80.  
81.public void destroy()   
82.{   
83.   filterConfig = null;   
84.   encoding = null;   
85.}   
86.  
87.     public void init(FilterConfig filterConfig) throws ServletException   
88.{   
89.          this.filterConfig = filterConfig;   
90.         this.encoding = filterConfig.getInitParameter("encoding");   
91.  
92.}   
93.}   
94.  
95.四、资源保护过滤器   
96.  
97.  
98.package catalog.view.util;   
99.  
100.import javax.servlet.Filter;   
101.import javax.servlet.FilterConfig;   
102.import javax.servlet.ServletRequest;   
103.import javax.servlet.ServletResponse;   
104.import javax.servlet.FilterChain;   
105.import javax.servlet.ServletException;   
106.import javax.servlet.http.HttpServletRequest;   
107.import java.io.IOException;   
108.import java.util.Iterator;   
109.import java.util.Set;   
110.import java.util.HashSet;   
111.//   
112.import org.apache.commons.logging.Log;   
113.import org.apache.commons.logging.LogFactory;   
114.  
115./**  
116. * This Filter class handle the security of the application.  
117. *   
118. * It should be configured inside the web.xml.  
119. *   
120. * @author Derek Y. Shen  
121. */  
122.public class SecurityFilter implements Filter {   
123. //the login page uri   
124. private static final String LOGIN_PAGE_URI = "login.jsf";   
125.    
126. //the logger object   
127. private Log logger = LogFactory.getLog(this.getClass());   
128.    
129. //a set of restricted resources   
130. private Set restrictedResources;   
131.    
132. /**  
133.  * Initializes the Filter.  
134.  */  
135. public void init(FilterConfig filterConfig) throws ServletException {   
136.  this.restrictedResources = new HashSet();   
137.  this.restrictedResources.add("/createProduct.jsf");   
138.  this.restrictedResources.add("/editProduct.jsf");   
139.  this.restrictedResources.add("/productList.jsf");   
140. }   
141.    
142. /**  
143.  * Standard doFilter object.  
144.  */  
145. public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)   
146.   throws IOException, ServletException {   
147.  this.logger.debug("doFilter");   
148.     
149.  String contextPath = ((HttpServletRequest)req).getContextPath();   
150.  String requestUri = ((HttpServletRequest)req).getRequestURI();   
151.     
152.  this.logger.debug("contextPath = " + contextPath);   
153.  this.logger.debug("requestUri = " + requestUri);   
154.     
155.  if (this.contains(requestUri, contextPath) && !this.authorize((HttpServletRequest)req)) {   
156.   this.logger.debug("authorization failed");   
157.   ((HttpServletRequest)req).getRequestDispatcher(LOGIN_PAGE_URI).forward(req, res);   
158.  }   
159.  else {   
160.   this.logger.debug("authorization succeeded");   
161.   chain.doFilter(req, res);   
162.  }   
163. }   
164.    
165. public void destroy() {}    
166.    
167. private boolean contains(String value, String contextPath) {   
168.  Iterator ite = this.restrictedResources.iterator();   
169.     
170.  while (ite.hasNext()) {   
171.   String restrictedResource = (String)ite.next();   
172.      
173.   if ((contextPath + restrictedResource).equalsIgnoreCase(value)) {   
174.    return true;   
175.   }   
176.  }   
177.     
178.  return false;   
179. }   
180.    
181. private boolean authorize(HttpServletRequest req) {   
182.  
183.              //处理用户登录   
184.       /* UserBean user = (UserBean)req.getSession().getAttribute(BeanNames.USER_BEAN);  
185.    
186.  if (user != null && user.getLoggedIn()) {  
187.   //user logged in  
188.   return true;  
189.  }  
190.  else {  
191.   return false;  
192.  }*/  
193. }   
194.}


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 -->  
  <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，如下：
<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。