Q:

validating json using constraints annotations is not working

I am trying to validate a json when deserialize it using constraints annotations  but it doesn't seem to work. for example 
import com.fasterxml.jackson.annotation.JsonProperty;
import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;

public class SimpleFooRequest {

    @NotNull
    @JsonProperty(value = "count")
    @Min(value = 100,message = "must be min 10")
    private  Integer count;

    @NotNull
    private String name;
    public String getName() {return name; }
    public void setName(String name) { this.name = name; }
    public Integer getCount() {return count;}
    public void setCount(Integer count) {this.count = count;}
}

when trying to unmarshal the json
@Test
public void testFooRequest() throws Exception
{
  String fooJson = {"count":-10}
  ObjectMapper mapper = new ObjectMapper()
  SimpleFooRequest request = mapper.readValue(fooJson,SimpleFooRequest.class);
  assert request.getCount().equals(-10);//expected fail but it pass !!!
}

it seems to pass although I expected that the assertion will fail due to the count min value limitation . I also tried to put the annotations on the setters but got same results 
I have <mvc:annotation-driven /> and hibernate-validator-4.3.1.Final.jar in my dependencies
I know that I can create custom validator but I thought that for simple validations I can use the annotations . 
what do I need to do to make it work ? 

A:

Annotations are just meta-data. They're not programs that can perform any validation. The validator is the program that will make use of the meta-data. In a container, the container will manage the validator. In basic unit tests or standalones, you will need to manage the validator yourself. 
That being said, even a validator cannot stop the object from being created/populated (as you seem to be asserting in your test). It just validates that the value is valid. If not, the validator throws an exception and/or lists some constraint violations. Either the container, or you should handle what to do with the exceptions/violations. 
And AFAIK, there's no ObjectMapper configuration for automatic JSR-303 support while deserializing
A better unit test, might look something like
/*  ----- Using the Hibernate Validator implementation ----- */
@Test
public void testInvalidCount() throws Exception {
    final String json = "{\"count\":-10, \"name\":\"Stack\"}";
    ObjectMapper mapper = new ObjectMapper();
    ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
    Validator validator = factory.getValidator();

    SimpleFooRequest request = mapper.readValue(
                               json, SimpleFooRequest.class);
    Set<ConstraintViolation<SimpleFooRequest>> violations 
                             = validator.validate(request);
    Assert.assertEquals(1, violations.size());  
    Assert.assertEquals("must be min 10", 
            violations.iterator().next().getMessage());
}

See Getting started with Hibernate Validator for some more examples

