JPA Criteria ORDER BY排序

ORDER BY 子句用于对数据进行排序并按升序或降序排列它们。CriteriaQuery 接口提供 orderBy() 方法来定义排序的类型。

JPA Criteria ORDER BY排序示例

在这里，我们将对学生表执行几个 ORDER BY 操作。让我们假设该表包含以下记录：

StudentEntity实体类

package com.yiidian.pojo;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="student")
public class StudentEntity {  
  
    @Id
    private int s_id;  
    private String s_name;  
    private int s_age;  
      
    public StudentEntity(int s_id, String s_name, int s_age) {  
        super();  
        this.s_id = s_id;  
        this.s_name = s_name;  
        this.s_age = s_age;  
    }  
  
    public StudentEntity() {  
        super();  
    }  
  
    public int getS_id() {  
        return s_id;  
    }  
  
    public void setS_id(int s_id) {  
        this.s_id = s_id;  
    }  
  
    public String getS_name() {  
        return s_name;  
    }  
  
    public void setS_name(String s_name) {  
        this.s_name = s_name;  
    }  
  
    public int getS_age() {  
        return s_age;  
    }  
  
    public void setS_age(int s_age) {  
        this.s_age = s_age;  
    }
}  

persistence.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
             xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="Student_details">
        <class>com.yiidian.pojo.StudentEntity</class>
        <properties>
            <property name="javax.persistence.jdbc.driver"
                      value="com.mysql.jdbc.Driver" />
            <property name="javax.persistence.jdbc.url"
                      value="jdbc:mysql://localhost:3306/jpa?serverTimezone=UTC&amp;useSSL=false" />
            <property name="javax.persistence.jdbc.user" value="root" />
            <property name="javax.persistence.jdbc.password" value="root" />
            <property name="eclipselink.logging.level" value="SEVERE" />
            <property name="eclipselink.ddl-generation" value="create-or-extend-tables" />
        </properties>
    </persistence-unit>

</persistence>

按升序排序

package com.yiidian.test;

import com.yiidian.pojo.StudentEntity;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Root;
import java.util.*;

public class Asc {

    public static void main(String args[]) {
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("Student_details");
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        CriteriaBuilder cb = em.getCriteriaBuilder();
        CriteriaQuery<StudentEntity> cq = cb.createQuery(StudentEntity.class);

        Root<StudentEntity> stud = cq.from(StudentEntity.class);

        cq.orderBy(cb.asc(stud.get("s_age")));
        CriteriaQuery<StudentEntity> select = cq.select(stud);
        TypedQuery<StudentEntity> q = em.createQuery(select);
        List<StudentEntity> list = q.getResultList();

        System.out.print("s_id");
        System.out.print("\t s_name");
        System.out.println("\t s_age");

        for (StudentEntity s : list) {
            System.out.print(s.getS_id());
            System.out.print("\t" + s.getS_name());
            System.out.println("\t" + s.getS_age());
        }

        em.getTransaction().commit();
        em.close();
        emf.close();
    }
}  

输出结果为：

按降序排序

package com.yiidian.test;

import com.yiidian.pojo.StudentEntity;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Root;
import java.util.List;

public class Desc {

    public static void main(String args[]) {
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("Student_details");
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        CriteriaBuilder cb = em.getCriteriaBuilder();
        CriteriaQuery<StudentEntity> cq = cb.createQuery(StudentEntity.class);

        Root<StudentEntity> stud = cq.from(StudentEntity.class);

        cq.orderBy(cb.desc(stud.get("s_age")));
        CriteriaQuery<StudentEntity> select = cq.select(stud);
        TypedQuery<StudentEntity> q = em.createQuery(select);
        List<StudentEntity> list = q.getResultList();

        System.out.print("s_id");
        System.out.print("\t s_name");
        System.out.println("\t s_age");

        for (StudentEntity s : list) {
            System.out.print(s.getS_id());
            System.out.print("\t" + s.getS_name());
            System.out.println("\t" + s.getS_age());
        }

        em.getTransaction().commit();
        em.close();
        emf.close();
    }
}  

输出结果为：