JPA中实体类的一些配置

一.单表增删改查

（1）实体类

@Entity
@Table(name="erp_role") //数据库中表名，列名需要与实体类中列名对应，如不对应需要使用@Column注解配置
public class Role {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY) //主键生成策略
    private Integer id;
    private String name;
    private String description;
　　 //省略get和set方法
}
（2）测试类

public class Test {
    @org.junit.Test
    public void testAddRole(){
        Role role = new Role();
        role.setName("角色2");
        role.setDescription("角色2");

        EntityManagerFactory emf = Persistence.createEntityManagerFactory("jpa"); //读取Resource目录下META-INF文件夹中的persistence.xml文件中的配置信息
        EntityManager em = emf.createEntityManager();
        EntityTransaction tx = em.getTransaction();
        tx.begin();
        em.persist(role);
        tx.commit();

    }
    @org.junit.Test
    public void testGetRole(){
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("jpa");
        EntityManager em = emf.createEntityManager();
        EntityTransaction tx = em.getTransaction();
        tx.begin();
        //Query query = em.createNativeQuery("select * from erp_role",Role.class);
        TypedQuery<Role> query = em.createQuery("from Role",Role.class);
        List<Role> roles = query.getResultList();
        roles.forEach(role -> System.out.println(role.getName()));
        tx.commit();
    }
    @org.junit.Test
    public void testUpdateRole(){
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("jpa");
        EntityManager em = emf.createEntityManager();
        EntityTransaction tx = em.getTransaction();
        tx.begin();
        Role role = em.find(Role.class,5);
        role.setName("角色3");
        em.merge(role);
        tx.commit();
    }
    @org.junit.Test
    public void testRemoveRole(){
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("jpa");
        EntityManager em = emf.createEntityManager();
        EntityTransaction tx = em.getTransaction();
        tx.begin();
        Role role = em.find(Role.class,5);
        em.remove(role);
        tx.commit();
    }
}

二.带外键表的级联增加和删除
（1）实体类（订单和订单明细）

@Entity
@Table(name = "erp_order")
public class Order {
    @Id
    @GenericGenerator(strategy = "uuid",name = "idgen") //uuid主键生成策略
    @GeneratedValue(generator = "idgen")
    private String id;
    private String num;
    @OneToMany(mappedBy = "order",cascade = {CascadeType.PERSIST,CascadeType.REMOVE})
    private Set<OrderInfo> orderInfos = new HashSet<OrderInfo>();

    //省略set和set方法

}

@Entity
@Table(name = "erp_orderinfo")
public class OrderInfo {
    @Id
    @GenericGenerator(strategy = "uuid",name = "idgen")
    @GeneratedValue(generator = "idgen")
    private String id;
    private String name;
    @ManyToOne(cascade = CascadeType.PERSIST)
    @JoinColumn(name = "orderid")
    private Order order;

    //省略set和set方法

}

（2）测试类

public class OrderTest {
    private static EntityManagerFactory emf;
    private EntityManager em;
    private EntityTransaction tx;

    @BeforeClass
    public static void init() {
        emf = Persistence.createEntityManagerFactory("jpa");
    }

    @AfterClass
    public static void destory() {
        emf = null;
    }

    @Before
    public void setUp() {
        em = emf.createEntityManager();
        tx = em.getTransaction();
        tx.begin();
    }

    @After
    public void tearDown() {
        tx.commit();
        em.close();
    }

    @Test
    public void testAddOrder() {
        Order order = new Order();
        order.setNum("1002");

        OrderInfo orderInfo1 = new OrderInfo();
        orderInfo1.setName("商品1");
        OrderInfo orderInfo2 = new OrderInfo();
        orderInfo2.setName("商品2");

        orderInfo1.setOrder(order);
        orderInfo2.setOrder(order);

        order.getOrderInfos().add(orderInfo1);
        order.getOrderInfos().add(orderInfo2);
        em.persist(order);
        System.out.println(em.contains(order));
    }

    @Test
    public void testDeleteOrder() {
        Order order = em.find(Order.class, "2c8d9596614b411f01614b4122120000");
        em.remove(order);
    }
}