Controller_vs_RestController

Controller注解 返回值类型：

1. ModelAndView
   页面和数据整合的类型，使用模版引擎时可使用这种方式
2. void
   此时，可以进行forward转发，request.getRequestDispatcher(“forwardUrl”).forward(request, response)（页面url不变）
   也可以进行redirect重定向，response.sendRedirect(“redirectUrl”) (页面url会跳转)
   还可以通过response.getWriter.write()直接返回页面数据
3. String
   Controller注解下，返回字符串默认是逻辑视图名称，功能同返回ModelAndView
   也可以进行redirect重定向，response.sendRedirect(“redirectUrl”) (页面url会跳转)，此时返回值无用
   还可以进行forward转发，request.getRequestDispatcher(“forwardUrl”).forward(request, response)（页面url不变），此时返回值无用
4. 任意数据类型 + ResponseBody注解
   此时将返回值按照返回类型进行json解析，并返回json数据

@Controller
@RequestMapping(path = "/hehe")
public class TestController {

    @GetMapping(path = "test")
    @ResponseBody
    public String test(@RequestParam String name) {
        return "HELLO " + name;
    }

    @GetMapping(path = "testvoid")
    public void testVoid(HttpServletRequest request,
                         HttpServletResponse response,
                         @RequestParam String name) {
        response.setCharacterEncoding ( "utf-8" );
        response.setContentType ( "application/json; charset=utf-8" );
        try {
            response.getWriter ().write ( "response write data: " + name );
        } catch (IOException e) {
            e.printStackTrace ();
        }
    }

    @GetMapping(path = "redirect1")
    public  String redirect1(@RequestParam String name) {
        return "redirect:test?name=" + name;
    }

    @GetMapping(path = "redirect2")
    public  void redirect2(HttpServletRequest request,
                           HttpServletResponse response,
                           @RequestParam String name) {
        try {
            response.sendRedirect ( "/hehe/test?name=" + name );
        } catch (IOException e) {
            e.printStackTrace ();
        }
    }

    @GetMapping(path = "redirect3")
    public RedirectView redirect3(@RequestParam String name) {
        return new RedirectView ( "/hehe/test?name=" + name );
    }

    @GetMapping(path = "forward1")
    public  String forward1(@RequestParam String name) {
        return "forward:test";
    }

    @GetMapping(path = "forward2")
    public void forward2(
            HttpServletRequest request,
            HttpServletResponse response,
            @RequestParam String name) {
        try {
             request.getRequestDispatcher ( "/hehe/test" )
                    .forward ( request, response);
        } catch (ServletException e) {
            e.printStackTrace ();
        } catch (IOException e) {
            e.printStackTrace ();
        }
    }

}

RestController注解 相当于 Controller注解 + ResponseBody注解，会对返回值进行JSON化处理并直接返回数据

@RestController
public class TestRestController {
    @RequestMapping("/rest")
    public Map test() {
        return new HashMap (  );
    }
}