(4)删除对象 public void delete(){ EntityMangerFactory factory=Persistence.createEntityMangerFactory("itcast"); EntityManger em=factory.createEntityManger(); em.getTransaction().begin(); //开启事务 Person person=em.find(Person.class,1); em.remove(person); //删除 em.getTransaction().commit(); em.close(); factory.close(); }
注意导入的包,应该导入javax开头的包 (5)查询 public void query(){ EntityMangerFactory factory=Persisentce.createEntityMangerFactory("itcast"); EntityManger em=factory.createEntityManger(); Query query=em.createQuery("select o from Person o where o.id=?1"); //从第一条记录开始查起 query.setParameter(1,2); //分别对应第一个问号和id=2这条记录 List person=query.getResultList(); for(Person person:persons) System.out.println(person.getName()); //循环打印结果中的name值 em.close(); factory.close(); }
public void deletequery(){ EntityMangerFactory factory=Persistence.createEntityMangerFactory("itcast"); EntityManger em=factory.createEntityManger(); em.getTranscation().begin(); //开启事务 Query query=em.createQuery("delete from Person o where o.id=?1"); query.setParameter(1,2); query.executeUpdate(); em.getTransaction().commit(); em.close(); factory.close(); }
public void queryupdate(){ EntityMangerFactory factory=Persistence.createEntityMangerFactory("itcast"); EntityManger em=factory.createEntityManger(); em.getTransaction().begin(); Query query=em.createQuery("update Person o set o.name=:name where o.id=:id"); //另外一种方式 query.setParameter("name","xxx"); //将name的值设为xxx query.setParameter("id",3); query.executeUpdate(); em.getTransaction().commit(); em.close(); factory.close(); }