Conditional Validator

Problem

The constraints of the Bean Validation cannot be turned on/off programmatically or according to any condition of the model object.

The @GroupSequenceProvider annotation from Hibernate Validator (RI) allows you to emulate this feature, however, it is a bit boring and tiring implement a class for each validated model object.

Solution

An extension for Bean Validation 2.0 containing analogous annotations for each constraint. For example, if you want to apply @NotNull conditionally use @NotNullWhen(expression = "")

Currently, the constraint expression is provided by Commons Jexl. All provided expression must return a Boolean (true/false).

Whenever the expression returns true, Conditional Validator delegates to the provider (Hibernate Validator or Apache BVal) the corresponding validation. For example, when the @NotNulWhen expression is true, ConditionalValidator tells the provider to validate as @NotNull.

Usage

1. Add dependency to pom.xml

<!-- If you use Hibernate Validator (RI) -->
<dependency>
    <groupId>com.github.microtweak</groupId>
    <artifactId>conditional-validator-hv</artifactId>
    <version>${conditional-validator.version}</version>
</dependency>

<!-- If you use Apache BVal -->
<dependency>
    <groupId>com.github.microtweak</groupId>
    <artifactId>conditional-validator-bval</artifactId>
    <version>${conditional-validator.version}</version>
</dependency>

2. Add annotations Conditional Validator

@ConditionalValidate // Enable conditional validation on this class
public class User {

    private boolean notifyByEmail;

    @EmailWhen(expression = "notifyByEmail") // Add the conditional constraint and set the expression
    private String email;
    
    // Getters and Setters
}