Servlet过滤器大全

一、字符编码的过滤器

 import javax.servlet.*; 
 import java.io.IOException; 
 
/** *//** 
 * 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 
 */ 
 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"); 
 
 } 
 } 

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 --> 
 <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。