关于Java：springboot如何验证方法参数@RequestParams是否为空？

我们可以使用@Validated（类上）与@Valid（参数上）组合，再配合@NotBlank / @NotNull（可以自定义错误message），即可完美解决：

import .*

@Validated
public class CalculationController {

    @RequestMapping(value ="/calculate")
    @ResponseBody
    public CalculationResult calculate(
            @Valid @NotBlank @RequestParam(name ="op") String operation,
            @Valid @NotNull @RequestParam(name ="num1") Double num1,
            @Valid @NotNull @RequestParam(name ="num2") Double num2) {
        ("Operation:" + operation);
        Double calculate = (operation, num1, num2);
        return new CalculationResult(calculate);
    }
}

应该修改相应的@Test以测试"可能不为空"消息的数组，如下所示：

@Test
public void validates_all_parameters_are_set() throws Exception {
    ResponseEntity<String> response = ("/calculate?op=&num1=&num2=", );
    assertThat((), equalTo(HttpStatus.BAD_REQUEST));
    assertThat((), equalTo("{"error":["may not be null","may not be null"]}"));
}