package com.atguigu.jpa.test;
import java.util.Date;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import javax.persistence.Query;
import org.hibernate.ejb.QueryHints;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.atguigu.jpa.helloworld.Category;
import com.atguigu.jpa.helloworld.Customer;
import com.atguigu.jpa.helloworld.Department;
import com.atguigu.jpa.helloworld.Item;
import com.atguigu.jpa.helloworld.Manager;
import com.atguigu.jpa.helloworld.Order;
public class JPATest {
private EntityManagerFactory entityManagerFactory;
private EntityManager entityManager;
private EntityTransaction transaction;
@Before
public void init(){
entityManagerFactory = Persistence.createEntityManagerFactory("jpa-1");
entityManager = entityManagerFactory.createEntityManager();
transaction = entityManager.getTransaction();
transaction.begin();
}
@After
public void destroy(){
transaction.commit();
entityManager.close();
entityManagerFactory.close();
}
//可以使用 JPQL 完成 UPDATE 和 DELETE 操作.
@Test
public void testExecuteUpdate(){
String jpql = "UPDATE Customer c SET c.lastName = ? WHERE c.id = ?";
Query query = entityManager.createQuery(jpql).setParameter(1, "YYY").setParameter(2, 12);
query.executeUpdate();
}
//使用 jpql 内建的函数
@Test
public void testJpqlFunction(){
String jpql = "SELECT lower(c.email) FROM Customer c";
List<String> emails = entityManager.createQuery(jpql).getResultList();
System.out.println(emails);
}
@Test
public void testSubQuery(){
//查询所有 Customer 的 lastName 为 YY 的 Order
String jpql = "SELECT o FROM Order o "
+ "WHERE o.customer = (SELECT c FROM Customer c WHERE c.lastName = ?)";
Query query = entityManager.createQuery(jpql).setParameter(1, "YY");
List<Order> orders = query.getResultList();
System.out.println(orders.size());
}
/**
* JPQL 的关联查询同 HQL 的关联查询.
*/
@Test
public void testLeftOuterJoinFetch(){
String jpql = "FROM Customer c LEFT OUTER JOIN FETCH c.orders WHERE c.id = ?";
Customer customer =
(Customer) entityManager.createQuery(jpql).setParameter(1, 12).getSingleResult();
System.out.println(customer.getLastName());
System.out.println(customer.getOrders().size());
// List<Object[]> result = entityManager.createQuery(jpql).setParameter(1, 12).getResultList();
// System.out.println(result);
}
//查询 order 数量大于 2 的那些 Customer
@Test
public void testGroupBy(){
String jpql = "SELECT o.customer FROM Order o "
+ "GROUP BY o.customer "
+ "HAVING count(o.id) >= 2";
List<Customer> customers = entityManager.createQuery(jpql).getResultList();
System.out.println(customers);
}
@Test
public void testOrderBy(){
String jpql = "FROM Customer c WHERE c.age > ? ORDER BY c.age DESC";
Query query = entityManager.createQuery(jpql).setHint(QueryHints.HINT_CACHEABLE, true);
//占位符的索引是从 1 开始
query.setParameter(1, 1);
List<Customer> customers = query.getResultList();
System.out.println(customers.size());
}
//使用 hibernate 的查询缓存.
@Test
public void testQueryCache(){
String jpql = "FROM Customer c WHERE c.age > ?";
Query query = entityManager.createQuery(jpql).setHint(QueryHints.HINT_CACHEABLE, true);
//占位符的索引是从 1 开始
query.setParameter(1, 1);
List<Customer> customers = query.getResultList();
System.out.println(customers.size());
query = entityManager.createQuery(jpql).setHint(QueryHints.HINT_CACHEABLE, true);
//占位符的索引是从 1 开始
query.setParameter(1, 1);
customers = query.getResultList();
System.out.println(customers.size());
}
//createNativeQuery 适用于本地 SQL
@Test
public void testNativeQuery(){
String sql = "SELECT age FROM jpa_cutomers WHERE id = ?";
Query query = entityManager.createNativeQuery(sql).setParameter(1, 3);
Object result = query.getSingleResult();
System.out.println(result);
}
//createNamedQuery 适用于在实体类前使用 @NamedQuery 标记的查询语句
@Test
public void testNamedQuery(){
Query query = entityManager.createNamedQuery("testNamedQuery").setParameter(1, 3);
Customer customer = (Customer) query.getSingleResult();
System.out.println(customer);
}
//默认情况下, 若只查询部分属性, 则将返回 Object[] 类型的结果. 或者 Object[] 类型的 List.
//也可以在实体类中创建对应的构造器, 然后再 JPQL 语句中利用对应的构造器返回实体类的对象.
@Test
public void testPartlyProperties(){
String jpql = "SELECT new Customer(c.lastName, c.age) FROM Customer c WHERE c.id > ?";
List result = entityManager.createQuery(jpql).setParameter(1, 1).getResultList();
System.out.println(result);
}
@Test
public void testHelloJPQL(){
String jpql = "FROM Customer c WHERE c.age > ?";
Query query = entityManager.createQuery(jpql);
//占位符的索引是从 1 开始
query.setParameter(1, 1);
List<Customer> customers = query.getResultList();
System.out.println(customers.size());
}
@Test
public void testSecondLevelCache(){
Customer customer1 = entityManager.find(Customer.class, 1);
transaction.commit();
entityManager.close();
entityManager = entityManagerFactory.createEntityManager();
transaction = entityManager.getTransaction();
transaction.begin();
Customer customer2 = entityManager.find(Customer.class, 1);
}
//对于关联的集合对象, 默认使用懒加载的策略.
//使用维护关联关系的一方获取, 还是使用不维护关联关系的一方获取, SQL 语句相同.
@Test
public void testManyToManyFind(){
// Item item = entityManager.find(Item.class, 5);
// System.out.println(item.getItemName());
//
// System.out.println(item.getCategories().size());
Category category = entityManager.find(Category.class, 3);
System.out.println(category.getCategoryName());
System.out.println(category.getItems().size());
}
//多对所的保存
@Test
public void testManyToManyPersist(){
Item i1 = new Item();
i1.setItemName("i-1");
Item i2 = new Item();
i2.setItemName("i-2");
Category c1 = new Category();
c1.setCategoryName("C-1");
Category c2 = new Category();
c2.setCategoryName("C-2");
//设置关联关系
i1.getCategories().add(c1);
i1.getCategories().add(c2);
i2.getCategories().add(c1);
i2.getCategories().add(c2);
c1.getItems().add(i1);
c1.getItems().add(i2);
c2.getItems().add(i1);
c2.getItems().add(i2);
//执行保存
entityManager.persist(i1);
entityManager.persist(i2);
entityManager.persist(c1);
entityManager.persist(c2);
}
//1. 默认情况下, 若获取不维护关联关系的一方, 则也会通过左外连接获取其关联的对象.
//可以通过 @OneToOne 的 fetch 属性来修改加载策略. 但依然会再发送 SQL 语句来初始化其关联的对象
//这说明在不维护关联关系的一方, 不建议修改 fetch 属性.
@Test
public void testOneToOneFind2(){
Manager mgr = entityManager.find(Manager.class, 1);
System.out.println(mgr.getMgrName());
System.out.println(mgr.getDept().getClass().getName());
}
//1.默认情况下, 若获取维护关联关系的一方, 则会通过左外连接获取其关联的对象.
//但可以通过 @OntToOne 的 fetch 属性来修改加载策略.
@Test
public void testOneToOneFind(){
Department dept = entityManager.find(Department.class, 1);
System.out.println(dept.getDeptName());
System.out.println(dept.getMgr().getClass().getName());
}
//双向 1-1 的关联关系, 建议先保存不维护关联关系的一方, 即没有外键的一方, 这样不会多出 UPDATE 语句.
@Test
public void testOneToOnePersistence(){
Manager mgr = new Manager();
mgr.setMgrName("M-BB");
Department dept = new Department();
dept.setDeptName("D-BB");
//设置关联关系
mgr.setDept(dept);
dept.setMgr(mgr);
//执行保存操作
entityManager.persist(mgr);
entityManager.persist(dept);
}
@Test
public void testUpdate(){
Customer customer = entityManager.find(Customer.class, 10);
customer.getOrders().iterator().next().setOrderName("O-XXX-10");
}
//默认情况下, 若删除 1 的一端, 则会先把关联的 n 的一端的外键置空, 然后进行删除.
//可以通过 @OneToMany 的 cascade 属性来修改默认的删除策略.
@Test
public void testOneToManyRemove(){
Customer customer = entityManager.find(Customer.class, 8);
entityManager.remove(customer);
}
//默认对关联的多的一方使用懒加载的加载策略.
//可以使用 @OneToMany 的 fetch 属性来修改默认的加载策略
@Test
public void testOneToManyFind(){
Customer customer = entityManager.find(Customer.class, 9);
System.out.println(customer.getLastName());
System.out.println(customer.getOrders().size());
}
//若是双向 1-n 的关联关系, 执行保存时
//若先保存 n 的一端, 再保存 1 的一端, 默认情况下, 会多出 n 条 UPDATE 语句.
//若先保存 1 的一端, 则会多出 n 条 UPDATE 语句
//在进行双向 1-n 关联关系时, 建议使用 n 的一方来维护关联关系, 而 1 的一方不维护关联系, 这样会有效的减少 SQL 语句.
//注意: 若在 1 的一端的 @OneToMany 中使用 mappedBy 属性, 则 @OneToMany 端就不能再使用 @JoinColumn 属性了.
//单向 1-n 关联关系执行保存时, 一定会多出 UPDATE 语句.
//因为 n 的一端在插入时不会同时插入外键列.
@Test
public void testOneToManyPersist(){
Customer customer = new Customer();
customer.setAge(18);
customer.setBirth(new Date());
customer.setCreatedTime(new Date());
customer.setEmail("mm@163.com");
customer.setLastName("MM");
Order order1 = new Order();
order1.setOrderName("O-MM-1");
Order order2 = new Order();
order2.setOrderName("O-MM-2");
//建立关联关系
customer.getOrders().add(order1);
customer.getOrders().add(order2);
order1.setCustomer(customer);
order2.setCustomer(customer);
//执行保存操作
entityManager.persist(customer);
entityManager.persist(order1);
entityManager.persist(order2);
}
/*
@Test
public void testManyToOneUpdate(){
Order order = entityManager.find(Order.class, 2);
order.getCustomer().setLastName("FFF");
}
//不能直接删除 1 的一端, 因为有外键约束.
@Test
public void testManyToOneRemove(){
// Order order = entityManager.find(Order.class, 1);
// entityManager.remove(order);
Customer customer = entityManager.find(Customer.class, 7);
entityManager.remove(customer);
}
//默认情况下, 使用左外连接的方式来获取 n 的一端的对象和其关联的 1 的一端的对象.
//可使用 @ManyToOne 的 fetch 属性来修改默认的关联属性的加载策略
@Test
public void testManyToOneFind(){
Order order = entityManager.find(Order.class, 1);
System.out.println(order.getOrderName());
System.out.println(order.getCustomer().getLastName());
}
*/
/**
* 保存多对一时, 建议先保存 1 的一端, 后保存 n 的一端, 这样不会多出额外的 UPDATE 语句.
*/
/*
@Test
public void testManyToOnePersist(){
Customer customer = new Customer();
customer.setAge(18);
customer.setBirth(new Date());
customer.setCreatedTime(new Date());
customer.setEmail("gg@163.com");
customer.setLastName("GG");
Order order1 = new Order();
order1.setOrderName("G-GG-1");
Order order2 = new Order();
order2.setOrderName("G-GG-2");
//设置关联关系
order1.setCustomer(customer);
order2.setCustomer(customer);
//执行保存操作
entityManager.persist(order1);
entityManager.persist(order2);
entityManager.persist(customer);
}
*/
/**
* 同 hibernate 中 Session 的 refresh 方法.
*/
@Test
public void testRefresh(){
Customer customer = entityManager.find(Customer.class, 1);
customer = entityManager.find(Customer.class, 1);
entityManager.refresh(customer);
}
/**
* 同 hibernate 中 Session 的 flush 方法.
*/
@Test
public void testFlush(){
Customer customer = entityManager.find(Customer.class, 1);
System.out.println(customer);
customer.setLastName("AA");
entityManager.flush();
}
//若传入的是一个游离对象, 即传入的对象有 OID.
//1. 若在 EntityManager 缓存中有对应的对象
//2. JPA 会把游离对象的属性复制到查询到EntityManager 缓存中的对象中.
//3. EntityManager 缓存中的对象执行 UPDATE.
@Test
public void testMerge4(){
Customer customer = new Customer();
customer.setAge(18);
customer.setBirth(new Date());
customer.setCreatedTime(new Date());
customer.setEmail("dd@163.com");
customer.setLastName("DD");
customer.setId(4);
Customer customer2 = entityManager.find(Customer.class, 4);
entityManager.merge(customer);
System.out.println(customer == customer2); //false
}
//若传入的是一个游离对象, 即传入的对象有 OID.
//1. 若在 EntityManager 缓存中没有该对象
//2. 若在数据库中也有对应的记录
//3. JPA 会查询对应的记录, 然后返回该记录对一个的对象, 再然后会把游离对象的属性复制到查询到的对象中.
//4. 对查询到的对象执行 update 操作.
@Test
public void testMerge3(){
Customer customer = new Customer();
customer.setAge(18);
customer.setBirth(new Date());
customer.setCreatedTime(new Date());
customer.setEmail("ee@163.com");
customer.setLastName("EE");
customer.setId(4);
Customer customer2 = entityManager.merge(customer);
System.out.println(customer == customer2); //false
}
//若传入的是一个游离对象, 即传入的对象有 OID.
//1. 若在 EntityManager 缓存中没有该对象
//2. 若在数据库中也没有对应的记录
//3. JPA 会创建一个新的对象, 然后把当前游离对象的属性复制到新创建的对象中
//4. 对新创建的对象执行 insert 操作.
@Test
public void testMerge2(){
Customer customer = new Customer();
customer.setAge(18);
customer.setBirth(new Date());
customer.setCreatedTime(new Date());
customer.setEmail("dd@163.com");
customer.setLastName("DD");
customer.setId(100);
Customer customer2 = entityManager.merge(customer);
System.out.println("customer#id:" + customer.getId());
System.out.println("customer2#id:" + customer2.getId());
}
/**
* 总的来说: 类似于 hibernate Session 的 saveOrUpdate 方法.
*/
//1. 若传入的是一个临时对象
//会创建一个新的对象, 把临时对象的属性复制到新的对象中, 然后对新的对象执行持久化操作. 所以
//新的对象中有 id, 但以前的临时对象中没有 id.
@Test
public void testMerge1(){
Customer customer = new Customer();
customer.setAge(18);
customer.setBirth(new Date());
customer.setCreatedTime(new Date());
customer.setEmail("cc@163.com");
customer.setLastName("CC");
Customer customer2 = entityManager.merge(customer);
System.out.println("customer#id:" + customer.getId());
System.out.println("customer2#id:" + customer2.getId());
}
//类似于 hibernate 中 Session 的 delete 方法. 把对象对应的记录从数据库中移除
//但注意: 该方法只能移除 持久化 对象. 而 hibernate 的 delete 方法实际上还可以移除 游离对象.
@Test
public void testRemove(){
// Customer customer = new Customer();
// customer.setId(2);
Customer customer = entityManager.find(Customer.class, 2);
entityManager.remove(customer);
}
//类似于 hibernate 的 save 方法. 使对象由临时状态变为持久化状态.
//和 hibernate 的 save 方法的不同之处: 若对象有 id, 则不能执行 insert 操作, 而会抛出异常.
@Test
public void testPersistence(){
Customer customer = new Customer();
customer.setAge(15);
customer.setBirth(new Date());
customer.setCreatedTime(new Date());
customer.setEmail("bb@163.com");
customer.setLastName("BB");
customer.setId(100);
entityManager.persist(customer);
System.out.println(customer.getId());
}
//类似于 hibernate 中 Session 的 load 方法
@Test
public void testGetReference(){
Customer customer = entityManager.getReference(Customer.class, 1);
System.out.println(customer.getClass().getName());
System.out.println("-------------------------------------");
// transaction.commit();
// entityManager.close();
System.out.println(customer);
}
//类似于 hibernate 中 Session 的 get 方法.
@Test
public void testFind() {
Customer customer = entityManager.find(Customer.class, 1);
System.out.println("-------------------------------------");
System.out.println(customer);
}
}
