1. Validation using Spring’s Validator interface

Spring features a Validator interface that you can use to validate objects. The Validator interface works using an Errors object so that while validating, validators can report validation failures to the Errors object.

2. data object:

public class KmailPostForm {
    private Integer kid;

    public KmailPostForm() {
    }

    public Integer getKid() {

        return kid;
    }

    public void setKid(Integer kid) {
        this.kid = kid;
    }
}

3. validator:

import com.maduar.springbootdemo.form.KmailPostForm;
import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;

public class KmailPostFormValidator implements Validator {
    @Override
    public boolean supports(Class<?> clazz) {
        return KmailPostForm.class.equals(clazz);
    }

    @Override
    public void validate(Object target, Errors errors) {
        ValidationUtils.rejectIfEmpty(errors, "kid", "kid.empty");
        KmailPostForm kmailPostForm = (KmailPostForm) target;
        if (kmailPostForm.getKid() == null) {
            errors.rejectValue("kid", "kid is null");
        } else if (kmailPostForm.getKid().intValue() < 0) {
            errors.rejectValue("kid", "kid < 0");
        }
    }
}

4. controller

@RestController
@RequestMapping(value = "/user")
public class UserController {

    @InitBinder
    public void initBinder(DataBinder dataBinder) {
        dataBinder.setValidator(new KmailPostFormValidator());
    }


    @PostMapping(value = "/helloPost/")
    public HttpEntity<?> helloPost(@Valid @RequestBody KmailPostForm kmailPostForm, BindingResult result) {

        if (result.hasErrors()) {
            return ResponseEntity.ok("error");
        }

        return ResponseEntity.ok("OK");
    }

}

a: springboot 版本 1.5.9.RELEASE

b: https://docs.spring.io/spring-framework/docs/current/spring-framework-reference/core.html#validation

java spring Validator