使用ResponseEntity作为的返回值的应用

@Controller
public class ResponseBodyTest {

    @ResponseBody
    @GetMapping("b1")
    public R b1(){
        //将方法的返回值转为json写入到响应体中
        return R.ok().put("msg","success");
    }

	@ResponseBody
    @GetMapping("b2")
    public ResponseEntity<String> b2(){
        HttpHeaders httpHeaders = new HttpHeaders();
        httpHeaders.setContentType(MediaType.TEXT_PLAIN);
        String str = "hello,world";
        ResponseEntity responseEntity = new ResponseEntity<String>(str,httpHeaders,HttpStatus.OK);
        return responseEntity;
    }

}

public class ResponseEntity<T> extends HttpEntity<T> {
    private final Object status;

    public ResponseEntity(HttpStatus status) {
        this((Object)null, (MultiValueMap)null, (HttpStatus)status);
    }

    public ResponseEntity(@Nullable T body, HttpStatus status) {
        this(body, (MultiValueMap)null, (HttpStatus)status);
    }

    public ResponseEntity(MultiValueMap<String, String> headers, HttpStatus status) {
        this((Object)null, headers, (HttpStatus)status);
    }

    public ResponseEntity(@Nullable T body, @Nullable MultiValueMap<String, String> headers, HttpStatus status) {
        super(body, headers);
        Assert.notNull(status, "HttpStatus must not be null");
        this.status = status;
    }

    private ResponseEntity(@Nullable T body, @Nullable MultiValueMap<String, String> headers, Object status) {
        super(body, headers);
        Assert.notNull(status, "HttpStatus must not be null");
        this.status = status;
    }

// 201:创建成功   Created
// 203 :没有认证   NON_AUTHORITATIVE_INFORMATION
// 204: 成功没有返回值 No-content  一般是delete,update时使用
.....

	@GetMapping("/categories")
    public ResponseEntity<List<Category>> getCategoryList(String token){
        return new ResponseEntity<>(categoryService.queryAll(), HttpStatus.OK);
    }

    @PostMapping("/categories")
    public ResponseEntity<Category> AddCategory(String token, @RequestBody Category category){
        
        return new ResponseEntity<>(categoryService.insert(category),HttpStatus.CREATED);
    }