过滤器 Filter

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Servlet JSF 浏览器 Cache Apache

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;
   }*/
}
}

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 {

     }

}


<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。

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