黎活明老师讲解的JPA源码

package junit.test; import java.util.Date; 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(); // -->sessionFactory-->session-->begin事务 em.getTransaction().begin(); em.persist(new Person("传智播客", new Date())); em.getTransaction().commit(); em.close(); factory.close(); } @Test public void getPerson() { EntityManagerFactory factory = Persistence.createEntityManagerFactory("itcast"); EntityManager em = factory.createEntityManager(); Person person = em.find(Person.class, 1); // get() System.out.println(person.getName()); em.close(); factory.close(); } @Test public void getPerson2() { EntityManagerFactory factory = Persistence.createEntityManagerFactory("itcast"); EntityManager em = factory.createEntityManager(); Person person = em.getReference(Person.class, 3); // load() 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(); //把实体变成游离状态 person.setName("老王"); em.merge(person); //用于把游离状态的对象更新同步到数据库 em.getTransaction().commit(); em.close(); factory.close(); } @Test public void delete() { EntityManagerFactory factory = Persistence.createEntityManagerFactory("itcast"); EntityManager em = factory.createEntityManager(); em.getTransaction().begin(); Person person = em.find(Person.class, 1); em.remove(person); //把托管状态的实体删掉 em.getTransaction().commit(); em.close(); factory.close(); } @Test public void query() { 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, 2); Person person = (Person) query.getSingleResult(); System.out.println(person.getName()); em.close(); factory.close(); } @Test public void deletequery() { 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, 2); query.executeUpdate(); em.getTransaction().commit(); em.close(); factory.close(); } @Test public void updatequery() { 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", 3); query.executeUpdate(); em.getTransaction().commit(); em.close(); factory.close(); } }