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Spring Java Bean Validation

Post Date: 17 Oct 2023


The Spring Framework, renowned for its versatility and efficiency, plays a pivotal role in offering comprehensive support for the Java Bean Validation API. Let’s embark on an exploration into the world of Bean Validation with Spring.

Java Bean Validation paves the way for unified validation by harnessing constraint declarations and metadata within Java applications. This framework allows developers to annotate domain model properties with declarative validation constraints. Subsequently, these constraints get enforced by the runtime. While there are numerous in-built constraints available, developers also have the liberty to architect custom constraints tailored to their specific needs.

Think of a basic ProductForm with things like productName and quantity. With Bean Validation, you can set rules like shown here:

public class ProductForm {

	private String productName;

	private int quantity;

With Bean Validation applied, validators will evaluate instances of this class in alignment with the stipulated constraints.

Configuring a Bean Validation Provider

Spring’s deep-rooted support for the Bean Validation API extends to the bootstrapping of a Bean Validation provider seamlessly integrated as a Spring bean. This facilitates the injection of jakarta.validation.ValidatorFactory or jakarta.validation.Validator at crucial junctions within your application where validation is paramount.

Consider leveraging the LocalValidatorFactoryBean to configure a default Validator as an intrinsic Spring bean:

public class ApplicationConfig {

	public LocalValidatorFactoryBean validator() {
		return new LocalValidatorFactoryBean();

This foundational configuration initiates bean validation employing its inherent bootstrap mechanism. The presence of a Bean Validation provider, like the Hibernate Validator, is assumed to exist within the classpath and is autonomously identified.

Injecting a Validator

The LocalValidatorFactoryBean effortlessly melds with both jakarta.validation.ValidatorFactory and jakarta.validation.Validator, along with Spring’s proprietary org.springframework.validation.Validator. Consequently, beans requiring to invoke validation mechanisms can comfortably access references to these interfaces.

For example, if you want to use the Bean Validation API directly:

public class MyService {

	private Validator validator;

Crafting Custom Constraints

Complex bean validation rules can be split into two parts:

  1. A @Constraint annotation proclaiming the constraint and its tunable properties.
  2. An embodiment of the jakarta.validation.ConstraintValidator interface scripting the constraint’s behavior.

Correlating a declaration with its realization, each @Constraint annotation cites a ConstraintValidator implementation class. Come runtime, the ConstraintValidatorFactory brings the referenced execution to life when the constraint annotation is discerned within your domain model.

By default, the LocalValidatorFactoryBean marshals a SpringConstraintValidatorFactory enabling Spring to originate ConstraintValidator instances. This bestows your tailor-made ConstraintValidators with the potency of dependency injection akin to other Spring beans.

Spring-Driven Method Validation

Spring’s rich ecosystem allows for the integration of the method validation feature, bolstered by Bean Validation 1.1 and, by extension, Hibernate Validator 4.3, via the MethodValidationPostProcessor bean definition:

public class ApplicationConfig {

	public MethodValidationPostProcessor validationPostProcessor() {
		return new MethodValidationPostProcessor();

To qualify for the zenith of Spring-driven method validation, it’s crucial for all target classes to be festooned with Spring’s @Validated annotation.

Configuring a DataBinder

The DataBinder stands as a formidable tool for assimilating a Validator. Once harmonized, the Validator can be invoked by a simple call to binder.validate(). Any ensuing validation discrepancies are autonomously appended to the binder’s BindingResult.

For Example:

Foo target = new Foo();
DataBinder binder = new DataBinder(target);
binder.setValidator(new FooValidator());

// bind to the target object

// initiate validation on the target object

// acquire BindingResult encompassing any validation pitfalls
BindingResult results = binder.getBindingResult();

When you need to combine general bean validation settings with a specific Spring Validator set up on a DataBinder, check out the Spring MVC Validation guide.

In Conclusion

The article delves deep into the world of Java Bean Validation within the Spring Framework. At its heart, Bean Validation offers a standardized way to enforce validation rules, making sure our Java applications are robust and error-free. By leveraging annotations, developers can effortlessly specify constraints on their domain models, ensuring that data adheres to predefined rules.

Spring Framework not only supports the core Bean Validation API but also provides extensive capabilities to integrate it smoothly into applications. Whether it’s configuring a default validation provider, injecting validators, or setting up custom constraints, Spring has got it covered. Additionally, there’s a special emphasis on method validation driven by Spring, which requires some AOP considerations but offers fine-grained control.

Furthermore, when it comes to integrating with Spring MVC, there’s a seamless bridge ensuring our web applications benefit from the same robust validation mechanisms. This ensures consistent and reliable data throughout an application, from the backend models to the front-end user interfaces.

Lastly, always remember that while the framework provides tools and conventions, it’s up to developers to use them judiciously, ensuring applications are not only functional but also reliable and user-friendly.

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