java - 当前没有交易 Activity

Question

所以我这里有这段代码

User us = new User();
            us.setId(id1);
            us.setUsername(userNameTextField.getText());
            us.setPassowrd(passwordFormattedTextField.getText());
            us.setLevel(levelComboBox.getSelectedItem().toString());
            us.setEmpid(getCurrentEmp());
            getCurrentEmp().getUserCollection().add(us);
            em.getTransaction().begin();               
            em.persist(getCurrentEmp());
            em.flush();
            em.getTransaction().commit();

但是当我尝试提交时我得到了这个错误

Exception Description: No transaction is currently active
at org.eclipse.persistence.internal.jpa.transaction.EntityTransactionWrapper.throwCheckTransactionFailedException(EntityTransactionWrapper.java:87)
at org.eclipse.persistence.internal.jpa.transaction.EntityTransactionWrapper.checkForTransaction(EntityTransactionWrapper.java:50)
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.checkForTransaction(EntityManagerImpl.java:2015)
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.flush(EntityManagerImpl.java:846)

我没有得到 y 因为我已经调用了 entitymanager 实例如下

em = emi.getInstance();

来自这个类(class)

public class EmInstance {
EntityManager em;
public EntityManager getInstance(){
em = Persistence.createEntityManagerFactory("samplePU").createEntityManager();
return em;
} 

我的问题是，每当我想使用它时，如何使事务处于 Activity 状态，例如在提交、更新或任何其他事务过程时。我正在使用 eclipselink 及其桌面应用程序

Answer 1

您确定两次调用 em.getTransaction() 会返回相同的交易吗？尝试:

EntityTransaction etx = em.getTransaction();
etx.begin();
...
etx.commit();