在 SQL 语句中，使用 order by 语句用于对结果集进行排序。JPQL 中也支持使用 order by 语句对结果进行排序，默认按照升序（ASC）对记录进行排序。如果您希望按照降序对记录进行排序，可以使用 DESC 关键字。
（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;
}实例1：根据用户薪水降序排序，代码如下：
public class JPQLDemo7 {
/** 持久化单元名称 */
private static final String PERSISTENCE_NAME = "openJPA2";
public static void main(String[] args) {
EntityManagerFactory factory = Persistence.createEntityManagerFactory(
PERSISTENCE_NAME, System.getProperties());
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
// 根据薪水 salary 递减排序
TypedQuery<User> query = em.createQuery(
"Select u from User u order by u.salary desc", User.class);
for(User user : query.getResultList()) {
System.out.println(user);
}
em.getTransaction().commit();
factory.close();
System.out.println("finished.");
}
}输出 SQL 语句如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 ORDER BY t0.salary DESC
User{id=6, name='用户-5', age=73, salary=8892.097}
User{id=2, name='用户-1', age=80, salary=7253.2427}
User{id=1, name='用户-0', age=56, salary=7251.132}
User{id=9, name='用户-8', age=79, salary=7199.551}
User{id=10, name='用户-9', age=26, salary=6327.472}
User{id=3, name='用户-2', age=44, salary=5855.36}
User{id=7, name='用户-6', age=77, salary=5494.797}
User{id=4, name='用户-3', age=10, salary=4105.1895}
User{id=8, name='用户-7', age=80, salary=3047.556}
User{id=5, name='用户-4', age=53, salary=2927.5222}实例2：先根据用户薪水降序排序，然后根据用户年龄升序排序。代码如下：
public class JPQLDemo7 {
/** 持久化单元名称 */
private static final String PERSISTENCE_NAME = "openJPA2";
public static void main(String[] args) {
EntityManagerFactory factory = Persistence.createEntityManagerFactory(
PERSISTENCE_NAME, System.getProperties());
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
// 先根据用户薪水降序排序，然后根据用户年龄排序
TypedQuery<User> query = em.createQuery(
"Select u from User u order by u.salary desc, u.age asc", User.class);
for(User user : query.getResultList()) {
System.out.println(user);
}
em.getTransaction().commit();
factory.close();
System.out.println("finished.");
}
}输出 SQL 语句如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 ORDER BY t0.salary DESC, t0.age ASC
User{id=6, name='用户-5', age=73, salary=8892.097}
User{id=2, name='用户-1', age=80, salary=7253.2427}
User{id=1, name='用户-0', age=56, salary=7251.132}
User{id=9, name='用户-8', age=79, salary=7199.551}
User{id=10, name='用户-9', age=26, salary=6327.472}
User{id=3, name='用户-2', age=44, salary=5855.36}
User{id=7, name='用户-6', age=77, salary=5494.797}
User{id=4, name='用户-3', age=10, salary=4105.1895}
User{id=8, name='用户-7', age=80, salary=3047.556}
User{id=5, name='用户-4', age=53, salary=2927.5222}
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