如何使用Hibernate JPA线程安全进行数据库访问？

Z时代
2024-01-10
分类：问答

我想知道我需要做什么才能访问数据库线程安全。

这是我的Entity类：

@Entity
@Table(name = "students")
@NamedQuery(name = "Student.getAll", query = "SELECT s FROM Student s")
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;
    @Column(length = 32, name = "name")
    private String name;
    // ... constructor, getters and setters, toString ...
}

这是DbService类：

public class DbService {
    public EntityManager em = Persistence
                         .createEntityManagerFactory("MyPersistenceUnit")
                         .createEntityManager();
    public Student add(Student student) {
        EntityTransaction tx = em.getTransaction();
        tx.begin();
        Student studentFromDb = em.merge(student);
        tx.commit();
        return studentFromDb;
    }
    public void delete(long id) {
        EntityTransaction tx = em.getTransaction();
        tx.begin();
        em.remove(get(id));
        tx.commit();
    }
    public Student get(long id) {
        return em.find(Student.class, id);
    }
    public void update(Student student) {
        EntityTransaction tx = em.getTransaction();
        tx.begin();
        em.merge(student);
        tx.commit();
    }
    public List<Student> getAll() {
        TypedQuery<Student> namedQuery =
                     em.createNamedQuery("Student.getAll", Student.class);
        return namedQuery.getResultList();
    }
}

这是与DbService一起使用的类：

public class SomeDbWorker implements Runnable {
    @Override
    public void run() {
        DbService service = new DbService();
        // do something ...
        service.add( ... );
        service.delete( ... );
        service.getAll();
        // ...
    }
}