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);
    }