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 field validator?
As an example, how can you use the API to validate two bean properties are equal (such as validating a password field matches the password verify field).
In annotations, I'd expect something like:
public class MyBean {
@Size(min=6, max=50)
private String pass;
@Equals(property="pass")
private String passVerify;
}
Each field constraint should be handled by a distinct validator annotation, or in other words it's not suggested practice to have one field's validation annotation checking against other fields; cross-field validation should be done at the class level. Additionally, the JSR-303 Section 2.2 preferred way to express multiple validations of the same type is via a list of annotations. This allows the error message to be specified per match.
For example, validating a common form:
@FieldMatch.List({
@FieldMatch(first = "password", second = "confirmPassword", message = "The password fields must match"),
@FieldMatch(first = "email", second = "confirmEmail", message = "The email fields must match")
})
public class UserRegistrationForm {
@NotNull
@Size(min=8, max=25)
private String password;
@NotNull
@Size(min=8, max=25)
private String confirmPassword;
@NotNull
@Email
private String email;
@NotNull
@Email
private String confirmEmail;
}
The Annotation:
package constraints;
import constraints.impl.FieldMatchValidator;
import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.Documented;
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.TYPE;
import java.lang.annotation.Retention;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Target;
/**
* Validation annotation to validate that 2 fields have the same value.
* An array of fields and their matching confirmation fields can be supplied.
*
* Example, compare 1 pair of fields:
* @FieldMatch(first = "password", second = "confirmPassword", message = "The password fields must match")
*
* Example, compare more than 1 pair of fields:
* @FieldMatch.List({
* @FieldMatch(first = "password", second = "confirmPassword", message = "The password fields must match"),
* @FieldMatch(first = "email", second = "confirmEmail", message = "The email fields must match")})
*/
@Target({TYPE, ANNOTATION_TYPE})
@Retention(RUNTIME)
@Constraint(validatedBy = FieldMatchValidator.class)
@Documented
public @interface FieldMatch
{
String message() default "{constraints.fieldmatch}";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
/**
* @return The first field
*/
String first();
/**
* @return The second field
*/
String second();
/**
* Defines several <code>@FieldMatch</code> annotations on the same element
*
* @see FieldMatch
*/
@Target({TYPE, ANNOTATION_TYPE})
@Retention(RUNTIME)
@Documented
@interface List
{
FieldMatch[] value();
}
}
The Validator:
package constraints.impl;
import constraints.FieldMatch;
import org.apache.commons.beanutils.BeanUtils;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
public class FieldMatchValidator implements ConstraintValidator<FieldMatch, Object>
{
private String firstFieldName;
private String secondFieldName;
@Override
public void initialize(final FieldMatch constraintAnnotation)
{
firstFieldName = constraintAnnotation.first();
secondFieldName = constraintAnnotation.second();
}
@Override
public boolean isValid(final Object value, final ConstraintValidatorContext context)
{
try
{
final Object firstObj = BeanUtils.getProperty(value, firstFieldName);
final Object secondObj = BeanUtils.getProperty(value, secondFieldName);
return firstObj == null && secondObj == null || firstObj != null && firstObj.equals(secondObj);
}
catch (final Exception ignore)
{
// ignore
}
return true;
}
}