要使用JPA2检查对象是否被锁定,您可以使用以下方法:
LockModeType
枚举类型:import javax.persistence.LockModeType;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class JPALockDemo {
public static void main(String[] args) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("example-unit");
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
MyEntity myEntity = em.find(MyEntity.class, 1, LockModeType.PESSIMISTIC_WRITE);
// 检查对象是否被锁定
if (myEntity != null) {
System.out.println("对象已被锁定");
} else {
System.out.println("对象未被锁定");
}
em.getTransaction().commit();
em.close();
emf.close();
}
}
LockModeType
注解:import javax.persistence.LockModeType;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;
public class JPALockDemo {
public static void main(String[] args) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("example-unit");
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
Query query = em.createQuery("SELECT e FROM MyEntity e WHERE e.id = :id");
query.setParameter("id", 1);
query.setLockMode(LockModeType.PESSIMISTIC_WRITE);
MyEntity myEntity = query.getSingleResult();
// 检查对象是否被锁定
if (myEntity != null) {
System.out.println("对象已被锁定");
} else {
System.out.println("对象未被锁定");
}
em.getTransaction().commit();
em.close();
emf.close();
}
}
在这两个示例中,我们使用了悲观锁定(LockModeType.PESSIMISTIC_WRITE
)来锁定对象。如果对象被锁定,则表示对象已被修改或删除,否则表示对象未被锁定。
请注意,这些示例仅适用于JPA2。如果您使用的是不同的ORM框架,则可能需要使用不同的方法来检查对象是否被锁定。
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