JPA 黎活明JPA视频代码

package junit.test; import java.util.List; import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; import javax.persistence.Query; import org.junit.BeforeClass; import org.junit.Test; import cn.itcast.bean.Person; public class PersonTest { @BeforeClass public static void setUpBeforeClass() throws Exception { } @Test public void save(){ EntityManagerFactory factory=Persistence.createEntityManagerFactory("itcast"); EntityManager em=factory.createEntityManager(); em.getTransaction().begin(); em.persist(new Person("中文")); em.getTransaction().commit(); em.close(); factory.close(); } /**读取数据不需要开事务，有数据更改动作（添、删、改）时才开启事务**/ @Test public void getPerson(){ EntityManagerFactory factory=Persistence.createEntityManagerFactory("itcast"); EntityManager em=factory.createEntityManager(); Person person=em.find(Person.class,1); em.refresh(person);//若直接更改了数据库中的数据，应该用refresh刷新一下数据库的动态变化，保证输出正确结果 System.out.println(person.getName()); em.close(); factory.close(); } @Test public void getPerson2(){ EntityManagerFactory factory=Persistence.createEntityManagerFactory("itcast"); EntityManager em=factory.createEntityManager(); /**getReference方法返回一个代理对象，只有对该代理对象的属性访问时，才会从数据库中得到该条记录（即发生数据的加载行为）**/ Person person=em.getReference(Person.class,1); /**若查找不到id为1的记录，会在对该代理对象的属性访问时，抛出异常。**/ System.out.println(person.getName()); em.close(); factory.close(); } @Test public void updatePerson(){ EntityManagerFactory factory=Persistence.createEntityManagerFactory("itcast"); EntityManager em=factory.createEntityManager(); em.getTransaction().begin(); Person person=em.find(Person.class,1); person.setName("老张"); em.getTransaction().commit(); em.close(); factory.close(); } @Test public void updatePerson2(){ EntityManagerFactory factory=Persistence.createEntityManagerFactory("itcast"); EntityManager em=factory.createEntityManager(); em.getTransaction().begin(); Person person=em.find(Person.class,1); em.clear();//将实体管理器中的所有实体变为游离状态 /**游离状态的实体无法更新字段**/ person.setName("老陈"); em.merge(person);//将游离状态的实体同步更新进数据库中 em.getTransaction().commit(); em.close(); factory.close(); } @Test public void deletePerson(){ EntityManagerFactory factory=Persistence.createEntityManagerFactory("itcast"); EntityManager em=factory.createEntityManager(); em.getTransaction().begin(); Person person=em.find(Person.class,1); em.remove(person); em.getTransaction().commit(); em.close(); factory.close(); } /**JPQL语言**/ @Test public void queryPerson(){ EntityManagerFactory factory=Persistence.createEntityManagerFactory("itcast"); EntityManager em=factory.createEntityManager(); Query query=em.createQuery("select o from Person o where o.id=?1"); query.setParameter(1, 1); //Person person=(Person)query.getSingleResult(); // System.out.println(person.getName()); List<Person> persons=query.getResultList(); for(Person person:persons) { System.out.println(person.getName()); } em.close(); factory.close(); } @Test public void delete(){ EntityManagerFactory factory=Persistence.createEntityManagerFactory("itcast"); EntityManager em=factory.createEntityManager(); em.getTransaction().begin(); Query query=em.createQuery("delete from Person o where o.id=?1"); query.setParameter(1,1); query.executeUpdate(); em.getTransaction().commit(); em.close(); factory.close(); } @Test public void update(){ EntityManagerFactory factory=Persistence.createEntityManagerFactory("itcast"); EntityManager em=factory.createEntityManager(); em.getTransaction().begin(); Query query=em.createQuery("update Person o set o.name=:name where o.id=:id"); query.setParameter("name","xxx"); query.setParameter("id",2); query.executeUpdate(); em.getTransaction().commit(); em.close(); factory.close(); } }