* Strategy interface that specifies a converter that can convert from and to HTTP requests and responses.

   ////////////////@ResponseBody/////////////////////////////
	@ResponseBody
    @RequestMapping("testRequestBody")
    public String testRequestBody(){
        return "abc";
    }
////////////////////////@RequestBody///////////////////////////
    @RequestMapping("testRequestBody")
    public String testRequestBody(@RequestBody String body){
        System.out.println(body);
        return "SUCCESS";
    }
 

////////////HttpEntity/////////////// 將請求報文轉化為String型別物件
    @RequestMapping("testHttpEntity")
    public String testHttpEntity(HttpEntity<String> entity){

        System.out.println(entity.getHeaders().getContentLength());
        return "a";
    }

///////////////ResponseEntity/////////////////////  體現出的就是下載的感覺，就是將伺服器的資源回傳給客戶端
    @RequestMapping("testResponseEntity")
    public ResponseEntity<String> testResponseEntity(){

        ResponseEntity<String> responseEntity = new ResponseEntity<String>("hello world",
                HttpStatus.OK);
        return responseEntity;
    }