Java过滤器，用户登陆验证过滤等

1.简单的过滤：

java文件代码：

package com.yang.juping;

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.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Juping implements Filter{
 FilterConfig config=null;
  public void init(FilterConfig config) throws ServletException{
  
   this.config=config;
  }
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException{
   System.out.println(1111);
   HttpServletRequest req = (HttpServletRequest) request;    //把request,response转换为HttpServletRequest

   HttpServletResponse res = (HttpServletResponse) response;   
   res.sendRedirect("index.jsp");//指定要跳转的页面

  }
  public void destroy(){
  }

}

在web.xml写入

//当访问/index.jsp时，就转向com.yang.juping.Juping

<filter>
   <filter-name>jup</filter-name>
   <filter-class>com.yang.juping.Juping</filter-class>
  </filter>
  <filter-mapping>
   <filter-name>jup</filter-name>
  <url-pattern>/index.jsp</url-pattern>
  </filter-mapping>

 

 2：网上找的还没用过。

java 代码
一、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   
{   
}   
}   
  
二、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());   
     }   
    }   
}   
}   
  
三、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");   
  
}   
}   
  
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;  
   }*/  
}   
}