How to implement multiple JSR-303 validation messages for the same @Constraint?

Steve Chambers Published at Dev

Steve Chambers

I'm using JSR-303 validation (hibernate-validator) for an entity with a few different rules to be applied. Would rather not stack up multiple @Constraint annotations for these and instead use a single one, e.g. @MyEntityConstraint.

Problem is there really needs to be a different message for each type of validation failure but the message seems inextricably associated with the annotation:

public @interface MyEntityConstraint {
    String message() default "A single, unchangeable message per constraint???";
    // ...
}

Is there any way round this or am I doomed to have:

@MyEntityConstraint1
@MyEntityConstraint2
// ...
@MyEntityConstraintn
@Entity
public class MyEntity {
    // ...
}

Steve Chambers

As suggested by Hardy, this can be done simply enough using ConstraintValidatorContext - as below:

@Override
public boolean isValid(MyEntity myEntity, ConstraintValidatorContext context) {
    // Disable default ConstraintViolation so a customised message can be set instead.
    context.disableDefaultConstraintViolation();

    return checkConstraint1(myEntity, context)
           && checkConstraint2(myEntity, context)
           //...
           && checkConstraintn(myEntity, context);
}

// Note: A private method for each constraint decreases the cyclomatic complexity.
private boolean checkConstraint1(MyEntity myEntity, ConstraintValidatorContext context) {
    // Default validity is true until proven otherwise.
    boolean valid = true;

    if (/*<<Insert constraint #1 conditions (about myEntity) here>>*/) {
        valid = false;
        context.buildConstraintViolationWithTemplate(
           "<<Insert constraint #1 failure message here>>").addConstraintViolation();
    }

    return valid;
}

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