@Data
class MyUser {

    @Size(min = 3, max = 15)
    private String name;

}


@Data
class MyUser2 {

    @Length(min = 3, max = 15)
    private String name;

}


@Data
class MyUser3 {

    //  the resulting column would be generated as a VARCHAR(15) and trying to insert a longer string would result in an SQL error.
    // @Column only to specify table column properties as it doesn't provide validations.
    // we can use @Column together with @Size to specify database column property with bean validation.
    @Column(length = 15)
    private String name;

}

import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;

import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import java.util.Set;

import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

/**
 * @description
 */


@Slf4j
class MyUserValidationTest {


    private final Validator validator = Validation.buildDefaultValidatorFactory().getValidator();


    @Test
    public void testSize() {

        MyUser myUser = new MyUser();
        myUser.setName("mary mary mary mary");

        Set<ConstraintViolation<MyUser>> violations = validator.validate(myUser);


        assertThat(violations.size()).isEqualTo(1);
        assertFalse(violations.isEmpty());

        for (ConstraintViolation<?> error : violations) {
            log.error(error.getPropertyPath() + ": " + error.getMessage());
        }

    }



    @Test
    public void testLength() {

        MyUser2 myUser = new MyUser2();
        myUser.setName("mary mary mary mary");

        Set<ConstraintViolation<MyUser2>> violations = validator.validate(myUser);


        assertThat(violations.size()).isEqualTo(1);
        assertFalse(violations.isEmpty());

        for (ConstraintViolation<?> error : violations) {
            log.error(error.getPropertyPath() + ": " + error.getMessage());
        }

    }



    @Test
    public void testColumn() {

        MyUser3 myUser = new MyUser3();
        myUser.setName("mary mary mary mary");

        Set<ConstraintViolation<MyUser3>> violations = validator.validate(myUser);

        assertTrue(violations.isEmpty());
    }
}