Spring MVC过滤器-登录过滤

以下代码是继承OncePerRequestFilter实现登录过滤的代码：

 package com.test.spring.filter;

 import java.io.IOException;
 import java.io.PrintWriter;

 import javax.servlet.FilterChain;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.springframework.web.filter.OncePerRequestFilter;

 /**
  * 登录过滤
  *
  * @author geloin
  * @date 2012-4-10 下午2:37:38
  */
 public class SessionFilter extends OncePerRequestFilter {

     /*
      * (non-Javadoc)
      *
      * @see
      * org.springframework.web.filter.OncePerRequestFilter#doFilterInternal(
      * javax.servlet.http.HttpServletRequest,
      * javax.servlet.http.HttpServletResponse, javax.servlet.FilterChain)
      */
     @Override
     protected void doFilterInternal(HttpServletRequest request,
             HttpServletResponse response, FilterChain filterChain)
             throws ServletException, IOException {

         // 不过滤的uri
         String[] notFilter = new String[] { "login.html", "index.html" };

         // 请求的uri
         String uri = request.getRequestURI();

         // uri中包含background时才进行过滤
         if (uri.indexOf("background") != -1) {
             // 是否过滤
             boolean doFilter = true;
             for (String s : notFilter) {
                 if (uri.indexOf(s) != -1) {
                     // 如果uri中包含不过滤的uri，则不进行过滤
                     doFilter = false;
                     break;
                 }
             }
             if (doFilter) {
                 // 执行过滤
                 // 从session中获取登录者实体
                 Object obj = request.getSession().getAttribute("loginedUser");
                 if (null == obj) {
                     // 如果session中不存在登录者实体，则弹出框提示重新登录
                     // 设置request和response的字符集，防止乱码
                     request.setCharacterEncoding("UTF-8");
                     response.setCharacterEncoding("UTF-8");
                     PrintWriter out = response.getWriter();
                     String loginPage = "....";
                     StringBuilder builder = new StringBuilder();
                     builder.append("<script type=\"text/javascript\">");
                     builder.append("alert('网页过期，请重新登录！');");
                     builder.append("window.top.location.href='");
                     builder.append(loginPage);
                     builder.append("';");
                     builder.append("</script>");
                     out.print(builder.toString());
                 } else {
                     // 如果session中存在登录者实体，则继续
                     filterChain.doFilter(request, response);
                 }
             } else {
                 // 如果不执行过滤，则继续
                 filterChain.doFilter(request, response);
             }
         } else {
             // 如果uri中不包含background，则继续
             filterChain.doFilter(request, response);
         }
     }

 }

写完过滤器后，需要在web.xml中进行配置：

<filter>
    <filter-name>sessionFilter</filter-name>
    <filter-class>com.test.spring.filter.SessionFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>sessionFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>