# Spring ResponseEntity

### 1. ResponseEntity
>用法

@GetMapping("/hello")
ResponseEntity<String> hello() {
    return new ResponseEntity<>("Hello World!", HttpStatus.OK);
}

//所以根据不同场景返回不同状态
@GetMapping("/age")
ResponseEntity<String> age(
  @RequestParam("yearOfBirth") int yearOfBirth) {

    if (isInFuture(yearOfBirth)) {
        return new ResponseEntity<>(
          "Year of birth cannot be in the future", 
          HttpStatus.BAD_REQUEST);
    }

    return new ResponseEntity<>(
      "Your age is " + calculateAge(yearOfBirth), 
      HttpStatus.OK);
}

//可以设置http標頭
@GetMapping("/customHeader")
ResponseEntity<String> customHeader() {
    HttpHeaders headers = new HttpHeaders();
    headers.add("Custom-Header", "foo");

    return new ResponseEntity<>(
      "Custom header set", headers, HttpStatus.OK);
}

//ResponseEntity提供了两个内嵌的构建器接口: 
//HeadersBuilder 和其子接口 BodyBuilder
@GetMapping("/hello")
ResponseEntity<String> hello() {
    return ResponseEntity.ok("Hello World!");
}
//常用的http 回應碼
BodyBuilder accepted();
BodyBuilder badRequest();
BodyBuilder created(java.net.URI location);
HeadersBuilder<?> noContent();
HeadersBuilder<?> notFound();
BodyBuilder ok();

//可以能使用BodyBuilder status(int status) 方法设置http状态
//ResponseEntity BodyBuilder.body(T body)设置http响应体
@GetMapping("/age")
ResponseEntity<String> age(@RequestParam("yearOfBirth") int yearOfBirth) {
    if (isInFuture(yearOfBirth)) {
        return ResponseEntity.badRequest()
            .body("Year of birth cannot be in the future");
    }

    return ResponseEntity.status(HttpStatus.OK)
        .body("Your age is " + calculateAge(yearOfBirth));
}
//自定義標頭
@GetMapping("/customHeader")
ResponseEntity<String> customHeader() {
    return ResponseEntity.ok()
        .header("Custom-Header", "foo")
        .body("Custom header set");
}

資料來源:
[使用spring ResponseEntity处理http响应](https://blog.csdn.net/neweastsun/article/details/81142870)

###### tags: `Spring boot` `ResponseEntity`