Filter Designer生成头文件怎么用

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技术领航探索者 2024-11-06 11:01:25

文章标签 jbuilder import filter string encoding 文章分类 架构后端开发

问题：

1 什么过滤器？

2 过滤器的优点和缺点？

3 过滤器常用的地方？

4 如何使用jBuilder创建过滤器？

解决方案：

1 过滤器是一个对象，可以传输请求或修改响应。它可以在请求到达Servlet/JSP之前对其进行预处理，而且能够在响应离开Servlet/JSP之后对其进行后处理。所以如果你有几个Servlet/JSP需要执行同样的数据转换或页面处理的话，你就可以写一个过滤器类，然后在部署描述文件（web.xml）中把该过滤器与对应的Servlet/JSP联系起来。你可以一个过滤器以作用于一个或一组servlet，零个或多个过滤器能过滤一个或多个servlet。一个过滤器实现java.servlet.Filter接口并定义它的三个方法：1． void init(FilterConfig config) throws ServletException:在过滤器执行service前被调用，以设置过滤器的配置对象。2． void destroy();在过滤器执行service后被调用。3． void doFilter(ServletRequest req,ServletResponse res,FilterChain chain) throws IOException,ServletException;

2 过滤器的优点是可以节省代码，缺点是：对网站的性能是有影响的。

3 主要用于以下5个地方：

(1) 使浏览器不缓存页面的过滤器

/** 
* 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);    
}       
}    
   
(2) 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());    
     }    
    }    
}    
}    
   
(3) 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");    
   
}    
}    
   
(4) 资源保护过滤器    
   
   
package catalog.view.util;    
      
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; 
   }*/   
}    
}   
(5) 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。

4 使用jBuilder创建过滤器

package 
   untitled3;

 
  import 
   javax.servlet. 
  * 
  ;
 
  import 
   javax.servlet.http. 
  * 
  ;
 
  import 
   java.io. 
  * 
  ;
 
  import 
   java.util. 
  * 
  ;

 
  /** */ 
  /**
 * wgf
 * <p>Title: </p> 
 * 
 * <p>Description: </p> 
 * 
 * <p>Copyright: Copyright (c) 2008</p> 
 * 
 * <p>Company: </p>
 * 
 * @author not attributable
 * @version 1.0
 */ 
  
 
  public 
    
  class 
   Filter1
     
  extends 
   HttpServlet  
  implements 
   Filter  
  ... 
  {
  private FilterConfig filterConfig;
  //Handle the passed-in FilterConfig
  public void init(FilterConfig filterConfig) throws ServletException ...{
    this.filterConfig = filterConfig;
  }

  //Process the request/response pair
  public void doFilter(ServletRequest request, ServletResponse response,
                       FilterChain filterChain) ...{
    try ...{
      HttpServletRequest req = (HttpServletRequest) request;
      req.setCharacterEncoding("GBK");
      filterChain.doFilter(request, response);
    }
    catch (ServletException sx) ...{
      filterConfig.getServletContext().log(sx.getMessage());
    }
    catch (IOException iox) ...{
      filterConfig.getServletContext().log(iox.getMessage());
    }
  }

  //Clean up resources
  public void destroy() ...{
  }
}

Filter Designer生成头文件怎么用_jbuilder