Hibernate Validator – Java Bean Validation Example

Java example to use hibernate validator to validate Java bean fields. Bean validation API 2 (JSR-380) offers some popular annotations that can be attached to each bean property for the purpose of maintaining data integrity.

1. Maven dependencies

Below are required hibernate validator maven dependencies.

Bean validation allows expressions inside the error messages. To parse these expressions, we must add a dependency on both the expression language API and an implementation of that API. I have added these using javax.el-api specification which is implemented in javax.el from Jboss.

<!-- Java bean validation API - Spec -->
<dependency>
	<groupId>javax.validation</groupId>
	<artifactId>validation-api</artifactId>
	<version>2.0.1.Final</version>
</dependency>

<!-- Hibernate validator - Bean validation API Implementation -->
<dependency>
	<groupId>org.hibernate</groupId>
	<artifactId>hibernate-validator</artifactId>
	<version>6.0.11.Final</version>
</dependency>

<!-- Verify validation annotations usage at compile time -->
<dependency>
  <groupId>org.hibernate</groupId>
  <artifactId>hibernate-validator-annotation-processor</artifactId>
  <version>6.0.11.Final</version>
</dependency>

<!-- Unified Expression Language - Spec -->
<dependency>
	<groupId>javax.el</groupId>
	<artifactId>javax.el-api</artifactId>
	<version>3.0.1-b06</version>
</dependency>

<!-- Unified Expression Language - Implementation -->
<dependency>
	<groupId>org.glassfish.web</groupId>
	<artifactId>javax.el</artifactId>
	<version>2.2.6</version>
</dependency>

2. Hibernate Validator Example

2.1. Model annotated with validation annotations

package com.howtodoinjava.example.model;

import javax.validation.constraints.Email;
import javax.validation.constraints.NotEmpty;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;

public class User {

    @NotNull(message = "Please enter id")
    private Long id;

    @Size(max = 20, min = 3, message = "{user.name.invalid}")
    @NotEmpty(message = "Please enter name")
    private String name;

    @Email(message = "{user.email.invalid}")
    @NotEmpty(message = "Please enter email")
    private String email;

    public User(Long id, String name, String email) {
        super();
        this.id = id;
        this.name = name;
        this.email = email;
    }

    //Setters and Getters
}

2.2. Message resource

By default, all messages are resolved from ValidationMessages.properties file in classpath. If file does not exist, the message resolution has not happen.

user.name.invalid=Invalid Username
user.email.invalid=Invalid Email

2.3. Execute validation

Now let’s execute the bean validation on User instance.

package com.howtodoinjava.example;

import java.util.Set;

import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;

import com.howtodoinjava.example.model.User;

public class TestHibernateValidator 
{
    public static void main(String[] args) 
    {
        //Create ValidatorFactory which returns validator
        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
        
        //It validates bean instances
        Validator validator = factory.getValidator();

        User user = new User(null, "1", "abcgmail.com");

        //Validate bean
        Set<ConstraintViolation<User>> constraintViolations = validator.validate(user);

        //Show errors
        if (constraintViolations.size() > 0) {
            for (ConstraintViolation<User> violation : constraintViolations) {
                System.out.println(violation.getMessage());
            }
        } else {
            System.out.println("Valid Object");
        }
    }
}

Program output:

Please enter id
Invalid Email
Invalid Username

3. Custom resource bundles

By default, framework picks up validation messages from ValidationMessages.properties file in classpath. You may configure your own custom property files as below.

Put these two files in classpath i.e. messages.properties and otherMessages.properties. Now all messages will be resolved from these two property files.

Validator validator = Validation.byDefaultProvider()
        .configure()
        .messageInterpolator(
                new ResourceBundleMessageInterpolator(
                        new AggregateResourceBundleLocator(
                                Arrays.asList(
                                        "messages",
                                        "otherMessages"
                                )
                        )
                )
        )
        .buildValidatorFactory()
        .getValidator();

4. Message Interpolation

4.1. Message parameters resolution

During message resolution, you can use runtime values to make validation messages more meaningful. This parameter value resolution in messages happen in two ways:

1. To resolve values in annotation attributes, simply enclose the with curly braces. E.g. {min} or {max}.
2. To resolve field’s runtime value, use placeholder ${validatedValue}.

4.2) Parameter resolution example

• Property file with message and parameters.

  user.name.invalid='${validatedValue}' is an invalid name. It must be minimum {min} chars and maximum {max} chars.
  

• Bean field with validation annotation.

  @Size(max = 20, min = 3, message = "{user.name.invalid}")
  private String name;
  

• Resolved message in program output.

  User user = new User(23l, "xy", "abc@gmail.com");
  Set<ConstraintViolation<User>> constraintViolations = validator.validate(user);
  
  //Output
  
  'xy' is an invalid name. It must be minimum 3 chars and maximum 20 chars.
  

5. Hibernate Validator Annotations

Now when we know how to use hibernate validator in programmatic manner. Let’s go through all the annotations which you can use in bean classes.

5.1. Bean validation annotations

5.2. Hibernate validator specific annotations

In addition to the constraints defined by the Bean Validation API, Hibernate Validator provides several useful custom constraints which are listed below.

Drop me your questions in comments section.

Happy Learning !!

References:

Bean Validation 2.0
Hibernate Validator Annotation Processor