返回“错误请求”,但需要“未找到”

这里是我的自定义处理程序异常:

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;

@ResponseStatus(HttpStatus.NOT_FOUND)
public class ProductNotFoundException extends RuntimeException
{
    public ProductNotFoundException(String exception) {
        super(exception);
    }
}

所以什么时候扔 ProductNotFoundException 则响应状态必须为 404 . 因为我添加了注释:

@ResponseStatus(HttpStatus.NOT_FOUND)

此处为控制器:

 import com.google.gson.JsonParseException;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;

@PutMapping("/product")
    public ResponseEntity<Product> updateProduct(@RequestBody String payload) {
        Product product = getProduct(payload);
        Optional<Product> findProduct = productRepository.findById(product.getId());
        if (findProduct.isPresent()) {
            return new ResponseEntity<Product>(updateProduct, HttpStatus.OK);
        } else {
            String error = "Not found product with id = " + product.getId();
            throw new ProductNotFoundException(error);
        }
    }

ProductNotFoundException异常

但当我发送put请求时,产品id不存在,http响应:

{
  "message": "Not found product with id = 123"
}
// PUT http://127.0.0.1:9090/api/v1/product
// HTTP/1.1 400 
// Content-Type: application/json
// Transfer-Encoding: chunked
// Date: Wed, 09 Sep 2020 16:21:22 GMT
// Connection: close
// Request duration: 0.138291s

问题是:为什么http状态是 ? 404