JPA由实体生成表

    persistence.xml

<property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"></property>

<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>

 

<property name="hibernate.hbm2ddl.auto" value="update"/>

实体名不能有下划线、主键不能有约束（待更进一步的考证）

 

测试：

EntityManagerFactory factory = Persistence.createEntityManagerFactory("xxx");//persistence-unit name="xxx"
  EntityManager em = factory.createEntityManager();
  //em.getTransaction().begin();
  //em.persist(new User("haojy4"));
  //em.getTransaction().commit();
  em.close();
  factory.close();