spring boot correlation validation example - EitherRequired

DemoForm.java

package com.example.web;

import com.example.validation.EitherRequired;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
@EitherRequired(fields = {"input", "otherInput"})
public class DemoForm {

    private String input;
    private String otherInput;

}

EitherRequired.java

package com.example.validation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import javax.validation.Constraint;
import javax.validation.Payload;

@Documented
@Constraint(validatedBy = {EitherRequiredValidator.class})
@Target({ElementType.TYPE, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface EitherRequired {

    String message() default "{com.example.validation.EitherRequired.message}";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    String[] fields();

    @Target({ElementType.TYPE, ElementType.ANNOTATION_TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface List {
        EitherRequired[] value();
    }
}

EitherRequiredValidator.java

package com.example.validation;

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;

public class EitherRequiredValidator implements ConstraintValidator<EitherRequired, Object>{

    private String[] fields;
    private String message;

    @Override
    public void initialize(EitherRequired eitherRequired) {
        fields = eitherRequired.fields();
        message = eitherRequired.message();
    }

    @Override
    public boolean isValid(Object value, ConstraintValidatorContext context) {
        BeanWrapper beanWrapper = new BeanWrapperImpl(value);
        for (String field : fields) {
            Object fieldValue = beanWrapper.getPropertyValue(field);
            if (fieldValue != null) {
                if (fieldValue instanceof String) {
                    if (!((String)fieldValue).isEmpty()) {
                        return true;
                    }
                } else {
                    return true;
                }
            }
        }

        context.disableDefaultConstraintViolation();
        context.buildConstraintViolationWithTemplate(message)
                .addPropertyNode(fields[0]).addConstraintViolation();
        return false;
    }

}

gistfile1.txt

Reference URL:

https://terasolunaorg.github.io/guideline/public_review/ArchitectureInDetail/Validation.html#id11