Mastering Spring Boot: Unified Controllers, Validation, and Response Handling

Spring Boot controller methods receive requests via @GetMapping and @PostMapping under a common @RequestMapping prefix. The example controller shows a ProductInfoController with a GET method findById and a POST method findPage, illustrating how request parameters are bound to a VO object.

The annotations @RestController (equivalent to @Controller + @ResponseBody), @RequestMapping, @GetMapping, and @PostMapping are explained, as well as how JSON fields such as productId and productName are automatically mapped from the request body.

To improve front‑end collaboration, the article proposes a unified response format that adds a status code, a message msg, and a data payload. Raw entity JSON is contrasted with the wrapped structure, and a StatusCode interface plus a ResultCode enum (e.g., SUCCESS(1000, "请求成功")) are introduced to centralize status definitions.

The ResultVo class provides constructors for different scenarios: returning only a code/message, returning data with the default success code, or returning data with a custom StatusCode. This eliminates repetitive manual wrapping in controller methods.

Parameter validation is streamlined with @Validated and Bean Validation annotations such as @NotNull and @Min. When validation fails, Spring throws BindException, which is intercepted by a @RestControllerAdvice that extracts the first ObjectError and returns a ResultVo using ResultCode.VALIDATE_ERROR.

To avoid writing new ResultVo(...) in every method, a ResponseBodyAdvice implementation ( ControllerResponseAdvice) automatically wraps non‑ ResultVo responses. It treats String return types specially by converting the wrapped object to JSON. Methods annotated with a custom @NotControllerResponseAdvice are excluded from this automatic wrapping.

Business‑level exceptions are handled uniformly by defining an AppCode enum that implements StatusCode (e.g., APP_ERROR(2000, "业务异常")) and an APIException runtime exception that carries a code, a message, and a detailed error description. A second @RestControllerAdvice catches APIException and returns a ResultVo with the appropriate code and message.

Example usage shows throwing

new APIException(AppCode.ORDER_NOT_EXIST, "订单号不存在：" + orderId)

and receiving a JSON response like

{"code":2003,"msg":"订单不存在","data":"订单号不存在：1998"}

. The article also includes images illustrating the AOP interception flow and a health‑check endpoint that can be excluded from wrapping.