Cross field validation with Hibernate Validator (JSR 303)

Question

Is there an implementation of (or third-party implementation for) cross field validation in Hibernate Validator 4.x? If not, what is the cleanest way to implement a cross fi

Answer 1

If you’re using the Spring Framework then you can use the Spring Expression Language (SpEL) for that. I’ve wrote a small library that provides JSR-303 validator based on SpEL – it makes cross-field validations a breeze! Take a look at https://github.com/jirutka/validator-spring.

This will validate length and equality of the password fields.

@SpELAssert(value = "pass.equals(passVerify)",
            message = "{validator.passwords_not_same}")
public class MyBean {

    @Size(min = 6, max = 50)
    private String pass;

    private String passVerify;
}

You can also easily modify this to validate the password fields only when not both empty.

@SpELAssert(value = "pass.equals(passVerify)",
            applyIf = "pass || passVerify",
            message = "{validator.passwords_not_same}")
public class MyBean {

    @Size(min = 6, max = 50)
    private String pass;

    private String passVerify;
}

Answer 2

I don't have the reputation for commenting on the first answer but wanted to add that I have added unit tests for the winning answer and have the following observations:

• If you get the first or field names wrong then you get a validation error as though the values don't match. Don't get tripped up by spelling mistakes e.g.

@FieldMatch(first="invalidFieldName1", second="validFieldName2")

• The validator will accept equivalent data types i.e. these will all pass with FieldMatch:

private String stringField = "1";

private Integer integerField = new Integer(1)

private int intField = 1;

• If the fields are of an object type which does not implement equals, the validation will fail.

Answer 3

I'm surprised this isn't available out of the box. Anyway, here is a possible solution.

I've created a class level validator, not the field level as described in the original question.

Here is the annotation code:

package com.moa.podium.util.constraints;

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import javax.validation.Constraint;
import javax.validation.Payload;

@Target({TYPE, ANNOTATION_TYPE})
@Retention(RUNTIME)
@Constraint(validatedBy = MatchesValidator.class)
@Documented
public @interface Matches {

  String message() default "{com.moa.podium.util.constraints.matches}";

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

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

  String field();

  String verifyField();
}

And the validator itself:

package com.moa.podium.util.constraints;

import org.mvel2.MVEL;

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class MatchesValidator implements ConstraintValidator<Matches, Object> {

  private String field;
  private String verifyField;


  public void initialize(Matches constraintAnnotation) {
    this.field = constraintAnnotation.field();
    this.verifyField = constraintAnnotation.verifyField();
  }

  public boolean isValid(Object value, ConstraintValidatorContext context) {
    Object fieldObj = MVEL.getProperty(field, value);
    Object verifyFieldObj = MVEL.getProperty(verifyField, value);

    boolean neitherSet = (fieldObj == null) && (verifyFieldObj == null);

    if (neitherSet) {
      return true;
    }

    boolean matches = (fieldObj != null) && fieldObj.equals(verifyFieldObj);

    if (!matches) {
      context.disableDefaultConstraintViolation();
      context.buildConstraintViolationWithTemplate("message")
          .addNode(verifyField)
          .addConstraintViolation();
    }

    return matches;
  }
}

Note that I've used MVEL to inspect the properties of the object being validated. This could be replaced with the standard reflection APIs or if it is a specific class you are validating, the accessor methods themselves.

The @Matches annotation can then be used used on a bean as follows:

@Matches(field="pass", verifyField="passRepeat")
public class AccountCreateForm {

  @Size(min=6, max=50)
  private String pass;
  private String passRepeat;

  ...
}

As a disclaimer, I wrote this in the last 5 minutes, so I probably haven't ironed out all the bugs yet. I'll update the answer if anything goes wrong.