判断是否登录的拦截器SessionFilter

需要写个拦截器，当用户没有登录的时候某些页面是不能访问的
用法将需要登录后访问的文件全部放在一个文件夹中，这里是logined文件夹

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

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;
import javax.servlet.http.HttpServletResponse;

import com.tlt.app.bean.Useraccount;
import com.tlt.app.util.Constants;

public class SessionFilter implements Filter{
  private List list = new ArrayList();
  
  public void destroy() {
    // TODO Auto-generated method stub
  }

  public void doFilter(ServletRequest request, ServletResponse response,
      FilterChain chain) throws IOException, ServletException {
    // TODO Auto-generated method stub
    String path=((HttpServletRequest)request).getServletPath();
//    System.out.println("path="+path);
    for(int i=0;i<list.size();i++){
      if(path.indexOf((String)list.get(i))!=-1){//需要拦截
        if (((HttpServletRequest) request).getSession().getAttribute(Constants.USER_KEY) == null) {//session不存在需要拦截
          String contextPath=((HttpServletRequest)request).getContextPath();
//          System.out.println("ContextPath="+contextPath);
          ((HttpServletResponse)response).sendRedirect(contextPath+"/login.jsp?toPath="+servletPath);//记录下登录后需要跳转到的页面，比如：/logined/account.jsp
        }else{
          chain.doFilter(request, response);
        }
        break;
      }else{
        chain.doFilter(request, response);
      }
    }
    
  }

  public void init(FilterConfig filterConfig) throws ServletException {
    // TODO Auto-generated method stub
     //初始化需要拦截的文件夹
     String include = filterConfig.getInitParameter("include");
     if (include != null) {
        StringTokenizer st = new StringTokenizer(include, ",");
        list.clear();
        while (st.hasMoreTokens()) {
          list.add(st.nextToken());
        }
     }
    
  }

}

可以使用多个文件夹，只需要将<param-value>中的值之间用“,”隔开。

<filter>
    <filter-name>sessionFilter</filter-name>
    <filter-class>com.tlt.app.filter.SessionFilter</filter-class>
    <init-param>
      <param-name>include</param-name>
      <param-value>logined</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>sessionFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>