LocalValidatorFactoryBean implements both javax.validation.Validator and org.springframework.validation.Validator. You may inject a reference to one of these two interfaces into beans that need to invoke validation logic.

Inject a reference to javax.validation.Validator if you prefer to work with the JSR-303 API directly:

import javax.validation.Validator;

@Service
public class MyService {

    @Autowired
    private Validator validator;

}
				

Inject a reference to org.springframework.validation.Validator if your bean requires the Spring Validation API:

import org.springframework.validation.Validator;

@Service
public class MyService {

    @Autowired
    private Validator validator;

}
				

Each JSR-303 validation constraint consists of two parts. First, a @Constraint annotation that declares the constraint and its configurable properties. Second, an implementation of the javax.validation.ConstraintValidator interface that implements the constraint's behavior. To associate a declaration with an implementation, each @Constraint annotation references a corresponding ValidationConstraint implementation class. At runtime, a ConstraintValidatorFactory instantiates the referenced implementation when the constraint annotation is encountered in your domain model.

By default, the LocalValidatorFactoryBean configures a SpringConstraintValidatorFactory that uses Spring to create ConstraintValidator instances. This allows your custom ConstraintValidators to benefit from dependency injection like any other Spring bean.

Shown below is an example of a custom @Constraint declaration, followed by an associated ConstraintValidator implementation that uses Spring for dependency injection:

@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy=MyConstraintValidator.class)
public @interface MyConstraint {
}
				

import javax.validation.ConstraintValidator;

public class MyConstraintValidator implements ConstraintValidator {

    @Autowired;
    private Foo aDependency;

    ...
}
				

As you can see, a ConstraintValidator implementation may have its dependencies @Autowired like any other Spring bean.

The default LocalValidatorFactoryBean configuration should prove sufficient for most cases. There are a number of other configuration options for various JSR-303 constructs, from message interpolation to traversal resolution. See the JavaDocs of LocalValidatorFactoryBean more information on these options.

To trigger validation of a @Controller input, simply annotate the input argument as @Valid:

@Controller
public class MyController {

    @RequestMapping("/foo", method=RequestMethod.POST)
    public void processFoo(@Valid Foo foo) { ... }

}
				

Spring MVC will validate a @Valid object after binding so-long as an appropriate Validator has been configured.

	Note
	The @Valid annotation is part of the standard JSR-303 Bean Validation API, and is not a Spring-specific construct.

The Validator instance invoked when a @Valid method argument is encountered may be configured in two ways. First, you may call binder.setValidator(Validator) within a @Controller's @InitBinder callback. This allows you to configure a Validator instance per @Controller class:

@Controller
public class MyController {

    @InitBinder
    protected void initBinder(WebDataBinder binder) {
        binder.setValidator(new FooValidator());
    }
    
    @RequestMapping("/foo", method=RequestMethod.POST)
    public void processFoo(@Valid Foo foo) { ... }
	
}
				

Second, you may call setValidator(Validator) on the global WebBindingInitializer. This allows you to configure a Validator instance across all @Controllers:

<!-- Invokes Spring MVC @Controller methods -->
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="webBindingInitializer">
        <!-- Configures Spring MVC DataBinder instances -->
        <bean class="org.springframework.web.bind.support.ConfigurableWebBindingInitializer">
            <property name="validator" ref="validator" />
        </bean>
    </property>
</bean>
				

With JSR-303, the default javax.validation.Validator implementation is generic. A single instance typically coordinates the validation of all application objects that declare validation constraints. To configure such a general purpose Validator for use by Spring MVC, simply inject a LocalValidatorFactoryBean reference into the WebBindingInitializer.

A full configuration example showing injection of a JSR-303 backed Validator into Spring MVC is shown below:

<!-- Invokes Spring MVC @Controller methods -->
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="webBindingInitializer">
        <!-- Configures Spring MVC DataBinder instances -->
        <bean class="org.springframework.web.bind.support.ConfigurableWebBindingInitializer">
            <property name="validator" ref="validator" />
        </bean>
    </property>
</bean>

<!-- Creates the JSR-303 Validator -->
<bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean" />
				

With this configuration, anytime a @Valid @Controller input is encountered, it will be validated by the JSR-303 provider. JSR-303, in turn, will enforce any constraints declared against the input. Any ConstaintViolations will automatically be exposed as BindingResults renderable by standard Spring MVC form tags.