Spring JPA add custom method

I am trying to add custom method to my spring repository but it is throwing errors. Below are the code snippets I am using. CommonDAO has the extra method I am trying add. User is the entity on which I am trying to operate. Problem is Spring is treating the method as User entity's property not as a separate method. Could you please let me know what I am missing?

Repository Interfaces and Implementations

    public interface CommonDAO<T> {
              public T merge(T t);
         }

    public interface UserDAOJPA extends JpaRepository<User, Integer>, CommonDAO<User> {
        public User findByUsername(String userName);
    }


@Repository(value="jpaBean")
public class UserDAOImplJPA implements CommonDAO<User> {

    @PersistenceContext
    private EntityManager em;

    @Override
    public User merge(User user) {
        return em.merge(user);
    }
}

Service Class

@Service
public class UserManagerJPAImpl implements UserManager {

    @Autowired
    private UserDAOJPA userDAO;


    @Override
    @Transactional
    public void insertUser(User user) {
        userDAO.save(user);
    }

    @Override
    @Transactional
    public User getUserById(int userId) {
        return userDAO.findOne(userId);
    }

    @Override
    @Transactional
    public User getUser(String username) {
        return userDAO.findByUsername(username);
    }

    @Override
    @Transactional
    public List<User> getUsers() {
        return userDAO.findAll();
    }

    @Override
    @Transactional
    public User mergeUser(User user) {
        return userDAO.merge(user);
    }

    /**
     * @param userDAO the userDAO to set
     */
    public void setUserDAO(UserDAOJPA userDAO) {
        this.userDAO = userDAO;
    }

}

Test Class

public class TestTx {
    public static void main(String[] args) {
        ApplicationContext ctx =
                new ClassPathXmlApplicationContext("app-context.xml");
/*      UserManager userManagerTraditional =
                (UserManager) ctx.getBean("userManagerImpl");*/

        UserManager userManager =
                (UserManager) ctx.getBean("userManagerJPAImpl");

        User user = new User();
        user.setUsername("johndoe");
        user.setName("John Doe");

        userManager.insertUser(user);

        System.out.println("User inserted!");

        user = userManager.getUser("johndoe");

        System.out.println("\nUser fetched by username!"
                + "\nId: " + user.getId()
                + "\nUsername: " + user.getUsername()
                + "\nName: " + user.getName());

        user.setName("After change");
        userManager.mergeUser(user);
        //user = userManagerTraditional.getUserById(user.getId());

        System.out.println("\nUser fetched by ID!"
                + "\nId: " + user.getId()
                + "\nUsername: " + user.getUsername()
                + "\nName: " + user.getName());

        List<User> users = userManager.getUsers();

        System.out.println("\nUser list fetched!"
                + "\nUser count: " + users.size());
    }
}

Errors I am getting No property merge found for type User!

15:25:03,995 INFO a.LocalContainerEntityManagerFactoryBean: 462 - Closing JPA EntityManagerFactory for persistence unit 'testPU' Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userDAOJPA': Invocation of init method failed; nested exception is org.springframework.data.mapping.PropertyReferenceException: No property merge found for type User! at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1574) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:736) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480) at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:139) at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:83) at com.debopam.sprintx.TestTx.main(TestTx.java:14) Caused by: org.springframework.data.mapping.PropertyReferenceException: No property merge found for type User! at org.springframework.data.mapping.PropertyPath.(PropertyPath.java:75) at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:327) at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:307) at org.springframework.data.mapping.PropertyPath.from(PropertyPath.java:270) at org.springframework.data.mapping.PropertyPath.from(PropertyPath.java:241) at org.springframework.data.repository.query.parser.Part.(Part.java:76) at org.springframework.data.repository.query.parser.PartTree$OrPart.(PartTree.java:235) at org.springframework.data.repository.query.parser.PartTree$Predicate.buildTree(PartTree.java:373) at org.springframework.data.repository.query.parser.PartTree$Predicate.(PartTree.java:353) at org.springframework.data.repository.query.parser.PartTree.(PartTree.java:84) at org.springframework.data.jpa.repository.query.PartTreeJpaQuery.(PartTreeJpaQuery.java:61) at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:95) at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateIfNotFoundQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:206) at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$AbstractQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:73) at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.(RepositoryFactorySupport.java:347) at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:185) at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.initAndReturn(RepositoryFactoryBeanSupport.java:239) at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:225) at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet(JpaRepositoryFactoryBean.java:92) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1633) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1570) ... 12 more