JPA JPQL
JPA JPQL
一、JPA简介
JPQL语言，即 Java Persistence Query Language 的简称。JPQL 是一种和 SQL 非常类似的中间性和对象化查询语言，它最终会被编译成针对不同底层数据库的 SQL 查询，从而屏蔽不同数据库的差异。如果会hibernate的hql查询，那么jpql会上手的很快。
JPQL语言的语句可以是 select 语句、update 语句或delete语句，它们都通过 Query 接口封装执行。
Query接口封装了执行数据库查询的相关方法。调用 EntityManager 的 createQuery、create NamedQuery 及 createNativeQuery 方法可以获得查询对象，进而可调用 Query 接口的相关方法来执行查询操作。
二、实体类
user类
package com.kuang.pojo;
import org.hibernate.annotations.Generated;
import javax.persistence.*;
import java.util.Date;
@NamedQuery(name = "namedUser",query = "from User where id>?")
@Cacheable(true)
@Table(name = "User_01")
@Entity
public class User {
private int id;
private String name;
private int age;
private Date Birth;
private boolean sex;
@GeneratedValue(strategy=GenerationType.AUTO)
@Id
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Date getBirth() {
return Birth;
}
@Temporal(value = TemporalType.DATE )
public void setBirth(Date birth) {
Birth = birth;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
", Birth=" + Birth +
", sex=" + sex +
'}';
}
public boolean isSex() {
return sex;
}
public void setSex(boolean sex) {
this.sex = sex;
}
}
学生类
package com.kuang.pojo;
import javax.persistence.*;
@Entity
@Table(name = "JPA_STUDENT")
public class Student {
private Integer id;
private String lastName;
private Boolean sex;
private Integer age;
private Teacher teacher;
@JoinColumn(name = "TEACHER_ID")
@ManyToOne(fetch = FetchType.LAZY)
public Teacher getTeacher() {
return teacher;
}
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
@Id
@GeneratedValue
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(name = "LAST_NAME")
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public Boolean getSex() {
return sex;
}
public void setSex(Boolean sex) {
this.sex = sex;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}
二、JPQL的三种查询
1、createNamedQuery
根据实体类@NamedQuery(name = “namedUser”,query = “from User where id>?”)
2、createQuery
创建Query, 可以根据对象查询sql
3、createNativeQuery
根据本地sql 查询
测试
package com.kuang.test;
import com.kuang.pojo.Student;
import com.kuang.pojo.User;
import org.hibernate.ejb.QueryHints;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import javax.persistence.*;
import java.util.List;
public class TestJPQL {
private EntityManagerFactory entityManagerFactory;
private EntityManager entityManager;
private EntityTransaction transaction;
@Before
public void init(){
entityManagerFactory= Persistence.createEntityManagerFactory("jpaHello");
entityManager = entityManagerFactory.createEntityManager();
transaction= entityManager.getTransaction();
transaction.begin();
}
@After
public void destroy(){
transaction.commit();
entityManager.close();
entityManagerFactory.close();
}
@Test
public void testJPQL(){
// sql语句
String sql="from User";
// 创建Query对象
Query query = entityManager.createQuery(sql);
//
List<User> resultList = query.getResultList();
for (User user : resultList) {
System.out.println(user.getName());
}
}
@Test
public void testJPQL01(){
String sql="from User where id=?";
Query query = entityManager.createQuery(sql);
query.setParameter(1,1);
User user = (User) query.getSingleResult();
System.out.println(user.getName());
}
@Test
public void testJQOLNamed(){
Query query = entityManager.createNamedQuery("namedUser");
query.setParameter(1, 0);
List<User> list = query.getResultList();
for (User user : list) {
System.out.println(user.getName());
}
}
@Test
public void testJQOlNative(){
String jpql="select * from user_01";
Query query = entityManager.createNativeQuery(jpql);
List list = query.getResultList();
for (Object o : list) {
System.out.println(o);
}
}
@Test
public void testCache(){
Query query = entityManager.createNamedQuery("namedUser").setHint(QueryHints.HINT_CACHEABLE,true);
query.setParameter(1, 0);
List<User> list = query.getResultList();
for (User user : list) {
System.out.println(user.getName());
}
query = entityManager.createNamedQuery("namedUser").setHint(QueryHints.HINT_CACHEABLE,true);
query.setParameter(1, 0);
list = query.getResultList();
System.out.println(list.size());
}
@Test
public void leftTest(){
String sql="from Student stu left outer join fetch stu.teacher where stu.id =?";
Query query = entityManager.createQuery(sql);
query.setParameter(1,1);
List<Student> list = query.getResultList();
for (Student student : list) {
System.out.println(student.getLastName());
System.out.println(student.getTeacher().getName());
}
}
@Test
public void fucntionTest(){
String sql=" from Student stu left outer join fetch stu.teacher where stu.id =?";
Query query = entityManager.createQuery(sql);
query.setParameter(1,1);
List<Student> list = query.getResultList();
for (Student student : list) {
System.out.println(student.getLastName());
System.out.println(student.getTeacher().getName());
}
}
@Test
public void testRemove(){
String jpql="update Student stu set stu.lastName =? where stu.id =? ";
Query query = entityManager.createQuery(jpql);
query.setParameter(1,"HaHA");
query.setParameter(2,1);
query.executeUpdate();
}
}
四、增删改
query 对象的增删改可以通过executeUpdate来进行
@Test
public void testRemove(){
String jpql="update Student stu set stu.lastName =? where stu.id =? ";
Query query = entityManager.createQuery(jpql);
query.setParameter(1,"HaHA");
query.setParameter(2,1);
query.executeUpdate();
}