function create_qrcode(){ajax({type:'GET',url : "/api/user/get_login_barcode",                success : function(response){var rs = eval("("+response+")");if(rs.code == "0"){                        xxxxxxxx}}});        } 

然后在LoginFilter中进行拦截处理，代码如下：

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;/*** 登录过滤器** @author zhuwenjun 20140506**/
public class LoginFilter implements Filter {@Overridepublic void destroy() {}@Overridepublic void doFilter(ServletRequest req, ServletResponse response, FilterChain chain) throws IOException,ServletException {HttpServletRequest request = (HttpServletRequest) req;response.setContentType( "text/html; charset=utf-8" );response.setCharacterEncoding( "utf-8");//得到请求的URIString url=request.getRequestURI();//因为所有的API请求都会带 api的字符串，请求页面的路径不会携带这个参数，在这里做校验，如果是API的请求就直接转发到MiddleServlet中if(url.contains( "api/")){//将请求的参数给设置过去req.setAttribute( "path", url);req.getServletContext().getRequestDispatcher( "/servlet/MiddleServlet" ).forward(req, response);} else{chain.doFilter(req, response);return;}}@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}}

package com.baimi.walletadmin.pc;import java.io.IOException;
import java.util.ArrayList;
import java.util.List;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.apache.http.cookie.Cookie;
import org.apache.log4j.Logger;import com.baimi.walletadmin.pc.util.HttpsRequest;
import com.baimi.walletadmin.pc.util.RegexUtil;
import com.baimi.walletadmin.pc.util.Util;public class MiddleServlet extends HttpServlet {private Logger log_info = Logger.getLogger("base");@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String returnMsg = HttpsRequest.executeGet(getReqUrl(req), getCookie(req),new CookieUtil(req, resp));Util.returnMsg(resp, returnMsg);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String returnMsg = HttpsRequest.executePost(getReqUrl(req), getCookie(req),req.getInputStream(), new CookieUtil(req, resp));Util.returnMsg(resp, returnMsg);}private List<javax.servlet.http.Cookie> getCookie(HttpServletRequest request) {javax.servlet.http.Cookie[] requestCookies = ((HttpServletRequest) request).getCookies();List<javax.servlet.http.Cookie> cookies = new ArrayList<javax.servlet.http.Cookie>();if (requestCookies != null) {for (javax.servlet.http.Cookie cookie : requestCookies) {if (Constants.TOKEN_COOKIE_NAME.equals(cookie.getName()) || Constants.ZG_COOKIE_NAME.equals(cookie.getName())) {cookies.add(cookie);}}}return cookies;}//从HttpServletRequest中得到请求的url，并拼接成访问第三方API的urlprivate String getReqUrl(HttpServletRequest request) {String path = String.valueOf(request.getAttribute("path"));if (path.contains("api/")) {String retUrl = Constants.REQ_HOST + path.substring(path.indexOf("api/"), path.length());String params = request.getQueryString();if (RegexUtil.isEmpty(params)) {retUrl = retUrl + "?" + params;}return retUrl;} else {return null;}}//接口实现类class CookieUtil implements CookieCallBack {private HttpServletRequest request;private HttpServletResponse response;public CookieUtil(HttpServletRequest request, HttpServletResponse response) {super();this.request = request;this.response = response;}//登录第三方API之后要将第三方返回的cookie设置到HttpServletResponse中@Overridepublic void doLogin(List<Cookie> list) {for (Cookie cookie : list) {if (Constants.TOKEN_COOKIE_NAME.equals(cookie.getName()) || Constants.ZG_COOKIE_NAME.equals(cookie.getName())) {javax.servlet.http.Cookie cook = new javax.servlet.http.Cookie(cookie.getName(),cookie.getValue());cook.setPath("/");cook.setMaxAge(Constants.COOKIE_TIME);((HttpServletResponse) response).addCookie(cook);break;}}}//退出的操作需要将HttpServletResponse中的cookie给清空掉@Overridepublic void doLogout() {request.getSession().invalidate();// 清空sessionjavax.servlet.http.Cookie[] cookies = request.getCookies();if (cookies != null) {for (javax.servlet.http.Cookie cookie : cookies) {if (Constants.TOKEN_COOKIE_NAME.equals(cookie.getName())) {cookie.setMaxAge(0);cookie.setPath("/");response.addCookie(cookie);break;}}}}}
}