Javax @NotNull annotation usage

Question

I have a simple method to get a list of documents for a given companyId. Here is the method:

@Override
public List getDocumentL         


        

Answer 1

@NotNull Annotation,

1. A method should not return null.
2. A variable (like fields, local variables, and parameters) cannot hold null value.

Answer 2

If you @Inject a class with your method, its working as expected.

@Stateless
public class MyBean{ 
    @Inject
    TestClass test;
}

and

public class TestClass {
    public List<Documents> getDocumentList(@NotNull Integer companyId)
    {
        //...
    }
}

ConstraintViolationException when you call your method with null parameter:

WFLYEJB0034: EJB Invocation failed on component MyBean for method ...:
javax.ejb.EJBException: javax.validation.ConstraintViolationException:
1 constraint violation(s) occurred during method validation.

Answer 3

To activate parameter validation, simply annotate the class with @Validated

import org.springframework.validation.annotation.Validated;

Answer 4

From The Java EE 6 Tutorial:

The Bean Validation model is supported by constraints in the form of annotations placed on a field, method, or class of a JavaBeans component, such as a managed bean.

You should place your validation of a field related to a declared bean, something like this:

@Entity
@Table(name="users")
public class BackgammonUser {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long userId;

    @Column(name="username")
    @NotBlank
    private String userName;

    @NotBlank
    private String password;

    @NotNull
    private Boolean enabled;
}

The BackgammonUser is considered to be a bean.