Why i am getting null value when i am mocking or Inject the object .?

I am getting a null value when i am trying to Inject the Dao interface. Sample of code here when i am writing a test cases.

@Mock
private ServiceUriLocator serviceLocator;   
@Mock
private SessionDao sessionDao;
ActiveSession session;
AccountData accountdata;
@InjectMocks
Account account

This Above code when i am using inside Method like

@Test
public void testActivate()
 {
  Response response=account.activate(accountdata).
 }

 private Accountdata accountdata(){
 accountdata.setFirstName("Employee_name");
 accountdata.LastName("Employee_Last_Name");
 return accountdata;
    }

In above code account value is null that's why i am getting null pointer exception. Anybody can calrify why i am getting null value for injecting the mock value.