摘要DAO模式和Spring的“代理服务器无法转换为＆hellip;”rdquo;问题！

public interface AbstractDao<T>
{
  public T get(Serializable id);
  //other CRUD operations
}

public abstract class AbstractDaoJpaImpl<T> implements AbstractDao<T> , Serializable
{
  protected EntityManager em;

  protected Class<T> clazz;

  @SuppressWarnings("unchecked")
  public AbstractDaoJpaImpl()
  {
    ParameterizedType genericSuperclass = (ParameterizedType) getClass().getGenericSuperclass();
    this.clazz = (Class<T>) genericSuperclass.getActualTypeArguments()[0];
  }

  public abstract void setEntityManager(EntityManager em);  
  //implementations skipped
}

public interface PersonDao extends AbstractDao<Person>
{
  //empty
}

@Repository
public class PersonDaoImpl extends AbstractDaoJpaImpl<Person> implements PersonDao , OtherInterface
{
  @PersistenceContext(unitName="company")
  @Override
  public void setEntityManager(EntityManager em)
  {
    this.em = em;
  }

  @Override // implements OtherInterface.additionalMethods()
  public additionalMethods()
  {
    // implements...
  }
}

<tx:annotation-driven transaction-manager="transactionManager" /> 

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:app.xml"})
@TransactionConfiguration(transactionManager="transactionManager" , defaultRollback=false)
public class PersonDaoTest
{
  @Inject 
  PersonDao dao;

  @Test
  public void testAdditionalMethod()
  {
    PersonDaoImpl impl = (PersonDaoImpl) dao;
    System.out.println(impl.additionalMethod(...));
  }
}

(PersonDaoImpl) dao

java.lang.ClassCastException: $Proxy36 cannot be cast to foobar.PersonDaoImpl
    at foobar.PersonDaoTest.testAdditionalMethod(PersonDaoTest.java:36)

proxy-target-class="true"

<tx:annotation-driven>

<tx:annotation-driven transaction-manager="transactionManager" proxy-target-class="true"  />

Caused by: java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.reflect.ParameterizedType

ParameterizedType genericSuperclass = (ParameterizedType) getClass().getGenericSuperclass();