Bean Validation does't work

I'm currently learning spring but I'm stuck with the validation annotation that don't works with my bean. I really don't understand what missing and I would need a Hand :)

I have a controller :

@Controller
public class CirclesController {

    @RequestMapping(value = "/createCircle", method = RequestMethod.POST)
    public ModelAndView createCircle(@Valid Circle circle, BindingResult res) {

        if (res.hasErrors()) {
            System.out.println("Can't validate this form..");
        else
            System.out.println("Created new circle : " + circle);
    }
}

And a bean :

public class Circle {

    @Size(min = 5)                 // This is what I try to validate
    private String      name;

public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

I configured the web.xml

<listener>
    <listener-class>
    org.springframework.web.context.ContextLoaderListener
    </listener-class>
</listener>

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>
        classpath:conf/dao-context.xml
        classpath:conf/services-context.xml
        classpath:conf/beans-context.xml
    </param-value>
</context-param>

my prject looks like that :

the *-context.xml have the component-scan and anotation-config tags :

<context:component-scan base-package="com.circuleo.app.[package-name]">
</context:component-scan>
<context:annotation-config></context:annotation-config>
<tx:annotation-driven></tx:annotation-driven>

I have all the external libraries (hibernate, hibernate-api, javax.validation) and no error on the run time... but when I fill the field "name" wit less than 5 characters, I always get "Created new circle : Circle{name=NomDuCercle}" instead of "Can't validate this form..".