Spring MVC过滤器-登录过滤的代码实现

一个非常简单的登录权限拦截器，具体代码如下：

以下代码是继承OncePerRequestFilter实现登录过滤的代码：

/**
 *
 * @author geloin
 * @date 2012-4-10 下午2:37:38
 */
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> 

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