Want to give custom annotation at RequestBody Pojo class - spring

Question

We can give #valid annotation but I want to give custom annotation at #RequestBody.
Use case: In my person Pojo class, I have two fields firstname and lastname. so I want to validate pojo class in that way that if user has given value for any field (like given for lastname) then it's good. but Both field should not be empty. User should give value for at least one field (it is either or condition)
My Pojo class:
class Person {
private String firstName;
private String lastName;
}
we can't give #NotNull for both fields. so I want to give custom annotation at the class level.
In that validator, I will check both fields and will send the proper error message to User.

Answer 1

You can try Custom ConstraintValidator, simple example #ValidatePerson:
package com.example.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;
import javax.validation.Constraint;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import javax.validation.Payload;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
#RestController
#SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
#PostMapping
public Person doSomeThingPerson(#Validated #RequestBody Person person) {
return person;
}
#ValidatePerson
public static class Person {
private String firstName;
private String lastName;
public String getFirstName() {
return firstName;
}
public String getLastName() {
return lastName;
}
}
#Target({TYPE})
#Retention(RUNTIME)
#Constraint(validatedBy = {PersonValidator.class}) // you can use multiply validators
public #interface ValidatePerson {
String message() default "Invalid Person, firstName and lastName can't be null";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
public static class PersonValidator implements ConstraintValidator<ValidatePerson, Person> {
#Override
public boolean isValid(Person person, ConstraintValidatorContext context) {
return person.getFirstName() != null || person.getLastName() != null;
}
}
}
If firstName and lastName both null then:
{
"timestamp": 1560456328285,
"status": 400,
"error": "Bad Request",
"errors": [
{
"codes": [
"ValidatePerson.person",
"ValidatePerson"
],
"arguments": [
{
"codes": [
"person.",
""
],
"arguments": null,
"defaultMessage": "",
"code": ""
}
],
"defaultMessage": "Invalid Person, firstName and lastName can't be null",
"objectName": "person",
"code": "ValidatePerson"
}
],
"message": "Validation failed for object='person'. Error count: 1",
"path": "/"
}
Also you can customize exception with #ControllerAdvice