Java Bean Validation 2.0 – Hibernate Validator Example

Bean validation in Java is supported via JSR-303 (Bean Validation 1.0), JSR-349 (Bean Validation 1.1) and JSR 380 (Bean Validation 2.0).

In this post, we will learn to use hibernate validator to validate the fields in Java bean. Bean validation API offers some very useful annotations that can be applied on a bean property for the purpose of maintaining data integrity.

1. Maven

Given below are the 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. Bean Validation Example

2.1. Model annotated with JSR-380 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. Default Interpolation

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

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

2.3. Executing 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. We may configure the custom property files as below.

For example, put these two property files in classpath:

• messages.properties
• otherMessages.properties

Add both property files to ResourceBundleMessageInterpolator.

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

4. Custom Message Interpolation

4.1. Parameters resolution in runtime

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 value 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);
  

  Program Output.

  'xy' is an invalid name. It must be minimum 3 chars and maximum 20 chars.
  

5. Bean Validation Annotations List

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. Default 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 the comments section.

Happy Learning !!

References:

Bean Validation 2.0
Hibernate Validator Annotation Processor