本章节将介绍怎样利用 JPQL 实现批量操作。
下面实例将使用 user 表作为操作对象。
（1）配置 persistence.xml，如下：
<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.0"> <persistence-unit name="openJPA2" transaction-type="RESOURCE_LOCAL"> <!-- JPA提供者 --> <provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider> <!-- 声明实体类 --> <class>com.hxstrive.openjpa.entity2.User</class> <!-- 配置JPA数据库属性 --> <properties> <property name="openjpa.ConnectionURL" value="jdbc:mysql://localhost:3306/openjpa_learn?useSSL=false& serverTimezone=UTC&useUnicode=true&characterEncoding=UTF-8"/> <property name="openjpa.ConnectionDriverName" value="com.mysql.jdbc.Driver"/> <property name="openjpa.ConnectionUserName" value="root"/> <property name="openjpa.ConnectionPassword" value="aaaaaa"/> <property name="openjpa.Log" value="SQL=TRACE"/> <!-- 自动生成表 --> <property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)"/> <!-- 不使用加载时强化和编译时强化，使用运行时Unenhanced（不能发挥OpenJPA的最大效能，所以也不推荐） --> <property name="openjpa.ClassLoadEnhancement" value="false"/> <property name="openjpa.DynamicEnhancementAgent" value="false"/> <property name="openjpa.RuntimeUnenhancedClasses" value="supported"/> </properties> </persistence-unit> </persistence>
（2）用户表实体映射，代码如下：
@Data
@Entity
@Table
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
@Column
private String name;
@Column
private Integer age;
@Column
private Float salary;
}通过 createQuery() 方法执行 select 语句，查询 user 表中所有数据。代码如下：
private void select() {
EntityManagerFactory factory = Persistence.createEntityManagerFactory(
PERSISTENCE_NAME, System.getProperties());
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
TypedQuery<User> query = em.createQuery("select u from User u", User.class);
List<User> userList = query.getResultList();
for (User user : userList) {
System.out.println(user);
}
em.getTransaction().commit();
em.close();
factory.close();
System.out.println("finished.");
}运行上面代码输出 SQL 语句如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0
User{id=1, name='用户-0', age=56, salary=7251.132}
User{id=2, name='用户-1', age=93, salary=7253.2427}
User{id=3, name='用户-2', age=44, salary=5855.36}
User{id=4, name='用户-3', age=10, salary=4105.1895}
User{id=5, name='用户-4', age=53, salary=2927.5222}
User{id=6, name='用户-5', age=73, salary=8892.097}
User{id=7, name='用户-6', age=77, salary=5494.797}
User{id=8, name='用户-7', age=91, salary=3047.556}
User{id=9, name='用户-8', age=79, salary=7199.551}
User{id=10, name='用户-9', age=26, salary=6327.472}通过 createQuery() 方法执行 update 语句，将所有年龄大于80岁的用户的年龄设置为80岁。代码如下：
private void update() {
EntityManagerFactory factory = Persistence.createEntityManagerFactory(
PERSISTENCE_NAME, System.getProperties());
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
Query query = em.createQuery("update User u set u.age=80 where u.age > 80");
query.executeUpdate();
em.getTransaction().commit();
em.close();
factory.close();
System.out.println("finished.");
}运行上面代码输出 SQL 语句如下：
UPDATE User t0 SET t0.age = ? WHERE (t0.age > ?) [params=?, ?]
通过 createQuery() 方法执行 delete 语句，将所有年龄大于80岁的用户删除。代码如下：
private void delete() {
EntityManagerFactory factory = Persistence.createEntityManagerFactory(
PERSISTENCE_NAME, System.getProperties());
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
Query query = em.createQuery("delete from User u where u.age > 80");
query.executeUpdate();
em.getTransaction().commit();
em.close();
factory.close();
System.out.println("finished.");
}运行上面代码输出 SQL 语句如下：
DELETE t0 FROM User t0 WHERE (t0.age > ?) [params=?]
