Spring MVC過濾器-登錄過濾

以下代碼是繼承OncePerRequestFilter實現登錄過濾的代碼：

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;
  
/**
 * 登錄過濾
 * 
 * @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 {
  
        // 不過濾的uri
        String[] notFilter = new String[] { "login.html", "index.html" };
  
        // 請求的uri
        String uri = request.getRequestURI();
  
        // uri中包含background時才進行過濾
        if (uri.indexOf("background") != -1) {
            // 是否過濾
            boolean doFilter = true;
            for (String s : notFilter) {
                if (uri.indexOf(s) != -1) {
                    // 如果uri中包含不過濾的uri，則不進行過濾
                    doFilter = false;
                    break;
                }
            }
            if (doFilter) {
                // 執行過濾
                // 從session中獲取登錄者實體
                Object obj = request.getSession().getAttribute("loginedUser");
                if (null == obj) {
                    // 如果session中不存在登錄者實體，則彈出框提示重新登錄
                    // 設置request和response的字符集，防止亂碼
                    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('網頁過期，請重新登錄！');");
                    builder.append("window.top.location.href='");
                    builder.append(loginPage);
                    builder.append("';");
                    builder.append("</script>");
                    out.print(builder.toString());
                } else {
                    // 如果session中存在登錄者實體，則繼續
                    filterChain.doFilter(request, response);
                }
            } else {
                // 如果不執行過濾，則繼續
                filterChain.doFilter(request, response);
            }
        } else {
            // 如果uri中不包含background，則繼續
            filterChain.doFilter(request, response);
        }
    }
  
}

寫完過濾器后，需要在web.xml中進行配置：

<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>