Java从后台重定向（redirect）到另一个项目的方法

（1）通过ModelAndView跳转

 @RequestMapping("alipayforward")
     public ModelAndView alipayforward(HttpServletRequest req, HttpServletResponse resp) throws Exception {
         String contNo =req.getParameter("contNo");
         logger.info("访问/downloadRequestElecCont.action");
         String url = "redirect:http://baidu.com/downloadRequestElecCont.action?contNo="+contNo;
         return new ModelAndView(url);
     }

（2）通过HttpServletResponse跳转

 @RequestMapping("alipayforward/{contNo}")
     public void alipayforward(@PathVariable("contNo") String contNo, HttpServletRequest req, HttpServletResponse resp) throws Exception {
         //String contNo =req.getParameter("contNo"); //保单号
         logger.info("访问/downloadRequestElecCont.action");
         resp.sendRedirect("http://baidu.com/downloadRequestElecCont.action?contNo="+contNo);
     }

（3）通过redirect返回String类型跳转，注意这种方法不允许Spring控制器用@RestController注解，

因为@RestController相当于类中的所有方法都标注了@ResponseBody，这些方法不会返回一个视图，而是返回一个json对象，

这样的话只是在页面上打印出字符串，而不跳转。控制器用@Controller注解即可

 @RequestMapping("alipayforward")
     public String alipayforward(@RequestParam("contNo") String contNo, HttpServletRequest req, HttpServletResponse resp) throws Exception {
         //String contNo =req.getParameter("contNo"); //保单号
         logger.info("访问/downloadRequestElecCont.action");
         return "redirect:http://baidu.com/downloadRequestElecCont.action?contNo="+contNo;
     }

下面是关于传参问题

重定向传参为get方式，如果传参数较多，可以封装到map或modelMap中

 @RequestMapping(params = "action=alipayforward")
     public String alipayforward(Map modelMap){
         modelMap.put("userName", "呵呵");
         modelMap.put("password", "123456");
         modelMap.put("age", "25");
         return "redirect:http://localhost:8088/era/user/alipayforward4?modelMap="+modelMap;
     }

另一个项目用实体类对象接收

 @RequestMapping("alipayforward4")
     public void alipayforward4(User user, HttpServletRequest req) throws Exception {
         System.out.println(user.getPassword());
         String modelMap = req.getParameter("modelMap");
         System.out.println(modelMap);
     }