我正在使用JUnit测试DAO类，但是我得到了一个空指针异常，我不确定为什么，因为我已经初始化了服务类。以下是测试类：
public class RegisterTest {
    private UserDaoImpl userservice = new UserDaoImpl();
    @Mock
    JdbcTemplate jdbcTemplate;
    User user;
    @Before
    public void setUp() {
        user = new User();
    }
    @Test
    public void testSetAddress() {
        user.setAddress("A");
        assertEquals(user.getAddress(), "A");
    }
    @Test
    public void testSetEmail() {
        user.setEmail("B");
        assertEquals(user.getEmail(), "B");
    }
    @Test
    public void testSetFirstname() {
        user.setFirstname("C");
        assertEquals(user.getFirstname(), "C");
    }
    @Test
    public void testSetLastname() {
        user.setLastname("D");
        assertEquals(user.getLastname(), "D");
    }
    @Test
    public void testSetPassword() {
        user.setPassword("E");
        assertEquals(user.getPassword(), "E");
    }
    @Test
    public void testSetUsername() {
        user.setUsername("F");
        assertEquals(user.getUsername(), "F");
    }
    @Test
    public void testRegister() {
        userservice.register(user);
        String username = user.getUsername();
        assertEquals(userservice.findByUsername(username).size(), 1);
    }
}
以下是UserDaoImpl：
public class UserDaoImpl implements UserDao {
    @Autowired
    PasswordEncoder passwordEncoder;
    @Autowired
    DataSource datasource;
    @Autowired
    JdbcTemplate jdbcTemplate;
    public List<User> findByUsername(String username) {
        String sql = "select * from users where username='" + username + "'";
        List<User> users = jdbcTemplate.query(sql, new UserMapper());
        return users;
    }
    public int register(User user) {
        // If username is unique
        String uniqueusername = "select * from users where username='" + user.getUsername() + "'";
        List<User> users = jdbcTemplate.query(uniqueusername, new UserMapper());
        if (users.size() == 0) {
            // encode password
            String encryptedPassword = passwordEncoder.encode(user.getPassword());
            // Updating database with new user
            String sql = "insert into users values(?,?,?,?,?,?)";
            return jdbcTemplate.update(sql, new Object[]{
                    user.getUsername(),
                    encryptedPassword,
                    user.getFirstname(),
                    user.getLastname(),
                    user.getEmail(),
                    user.getAddress()});
        } else {
            return 0;
        }
    }
}
如何在测试类中注入该类？我猜空指针异常的原因是因为DAO类没有在测试类中被正确注入。

@RunWith(MockitoJunitRunner.class)
public class RegisterTest {

@InjectMocks
private UserDaoImpl userservice = new UserDaoImpl();