解决AJAX请求无法转发问题

今天遇到了一个问题，需要把收藏功能优化，在用户未登录的情况下点击收藏时跳转到登录界面。

踩了一些坑后发现由于AJAX请求异步刷新的原因，不支持转发和重定向。

解决办法

1、直接由前台判断是否转发

$.ajax({
    url:"/room/insertHotelCollectionByHotelId",
    contentType:"application/json;charset=UTF-8",
    data:'{"hotelId":'+hotelId+'}',
    dataType:"json",
    type:"post",
    success:function(data) {
    },
    error:function (data) {
        window.location.href="/userhtml/login.html";
    }
});

    @ResponseBody
    @RequestMapping("insertHotelCollectionByHotelId")
    public ResultData   insertHotelCollectionByHotelId(HttpServletRequest request, @RequestBody String  body) throws IOException, ServletException {
        ResultData resultData = new ResultData();
        Long userId = Long.parseLong(request.getSession().getAttribute("userId").toString());

        if (userId == null) {
            resultData.setCode(3);
            resultData.setMessage("数据为空");
        } else {
            Gson gson = new Gson();
            HotelCollection hotelCollection = gson.fromJson(body,HotelCollection.class);
            hotelCollection.setUserId(userId);
            roomService.insertHotelCollectionByHotelId(hotelCollection);
            resultData.setCode(0);
            resultData.setData(hotelCollection);
        }
        return resultData;
    }

2、后台过滤器判断这个请求是否为AJAX请求，如果是，则向前台发送包含这个信息的cookie，前台再根据cookie判断，决定是否转发。

	public class MyInterceptor extends HandlerInterceptorAdapter{
		//该方法是进入controller的必经之路。
		@Override
		public boolean preHandle(HttpServletRequest request,
				HttpServletResponse response, Object handler) throws Exception {
			if(是否登录了?){
				return true; 
			}else { //没有登录重定向到登录页面
				reDirect(request, response); 
				return false;
			}
		}
	
		@Override
		public void postHandle(HttpServletRequest request,
				HttpServletResponse response, Object handler,
				ModelAndView modelAndView) throws Exception {
			// TODO Auto-generated method stub
			super.postHandle(request, response, handler, modelAndView);
		}
	
		@Override
		public void afterCompletion(HttpServletRequest request,
				HttpServletResponse response, Object handler, Exception ex)
				throws Exception {
			// TODO Auto-generated method stub
			super.afterCompletion(request, response, handler, ex);
		}
		
		//对于请求是ajax请求重定向问题的处理方法
		public void reDirect(HttpServletRequest request, HttpServletResponse response) throws IOException{
			//获取当前请求的路径
			String basePath = request.getScheme() + "://" + request.getServerName() + ":"  + request.getServerPort()+request.getContextPath();
			//如果request.getHeader("X-Requested-With") 返回的是"XMLHttpRequest"说明就是ajax请求，需要特殊处理
			if("XMLHttpRequest".equals(request.getHeader("X-Requested-With"))){
				//告诉ajax我是重定向
				response.setHeader("REDIRECT", "REDIRECT");
				//告诉ajax我重定向的路径
				response.setHeader("CONTENTPATH", basePath+"/login.html");
				response.setStatus(HttpServletResponse.SC_FORBIDDEN);
			}else{
				response.sendRedirect(basePath + "/login.html");
			}
		}
	
	}

	var jqxhr;
	//设置ajax请求完成后运行的函数,
	$.ajaxSetup({ 
		complete:function(){
			if("REDIRECT" == jqxhr.getResponseHeader("REDIRECT")){ //若HEADER中含有REDIRECT说明后端想重定向，
				var win = window;
				while(win != win.top){
					win = win.top;
				}
				win.location.href = jqxhr.getResponseHeader("CONTENTPATH");//将后端重定向的地址取出来,使用win.location.href去实现重定向的要求
			}
	    }
	});

补充：

普通转发

//类的注解不能使用@RestController，要用@Controller
@RequestMapping(value="/test/test01/{name}" , method = RequestMethod.GET)
public String test(@PathVariable String name) {
    return "forword:/ceng/hello.html";
}

//类的注解可以使用@RestController，也可以使用@Controller
@RequestMapping(value="/test/test01/{name}" , method = RequestMethod.GET)
public void test(@PathVariable String name, HttpServletRequest request, HttpServletResponse response) throws Exception {
    request.getRequestDispatcher("/ceng/hello.html").forward(request,response);
}

普通重定向

//类的注解不能使用@RestController，要用@Controller
@RequestMapping(value="/test/test01/{name}" , method = RequestMethod.GET)
public String test(@PathVariable String name) {
    return "redirect:/ceng/hello.html";
}

//类的注解可以使用@RestController，也可以使用@Controller
@RequestMapping(value="/test/test01/{name}" , method = RequestMethod.GET)
public void test(@PathVariable String name, HttpServletResponse response) throws IOException {
    response.sendRedirect("/ceng/hello.html");
}

    @RequestMapping("/save2")
    public void save2(Account account, HttpServletRequest request, HttpServletResponse response) throws IOException {
        accountService.saveAccount(account);
        response.sendRedirect(request.getContextPath()+"/account/findAll");
        return;
    }

部分内容转载自：https://blog.csdn.net/qq_30306577/article/details/71693301
https://www.cnblogs.com/lu51211314/p/10482099.html