hibernate 和 jpa简介
hibernate 和 jpa简介
- 小引
- 什么是ORM思想？
- Hibernate概述
- JPA概述
- hibernate 和 jpa的关系
- jpa的常用对象
- JPA中的主键生成策略
- JPA的入门案例
- 配置文件(src下META-INF下persistence.xml 固定死的位置不能变)
- 实体类
- 测试Demo（DDL建表）
- JPA的CRUD
- 抽取工具类
- 增删改查方法
- JPA中的两种查询方式
- Hibernate 的CRUD 练习
- 配置文件
- 抽取工具类
- CURD
小引
长时间以来，人们解决持久层的方案，无论是jdbc、dbutils还是mybatis、jdbcTemplate，都无法跳出对SQL的高度关注，也就是说，大家始终要花费大量的时间去写简单的CRUD代码。因此，人们设想能不能通过某种方法，让我们不用再编写简单的CRUD语句而是直接建立某种对应关系实现表的操作，因此hibernate框架诞生了。
什么是ORM思想？
ORM（Object-Relational Mapping）
Object：java对象
Relational：关系型数据库
Mapping：映射（对应关系的映射）
ORM:通过操作实体类就能直接操作数据库，依据的是对应关系的建立
Hibernate概述
它是一个 开源的，轻量级的，基于ORM思想的企业级应用框架。通过实体类自动生成sql语句，实现程序员经过sql而操作数据库的可能。
JPA概述
JPA及java持久化API，是sun公司基于ORM思想提供的一套规范
hibernate 和 jpa的关系
jpa是一套接口和规范，hibernate是它其中一种的实现。
jpa的常用对象
Persistence
JPA的核心对象 主要负责创建 EntityManagerFactory
EntityManagerFactory
类似于SqlSessionFactory SqlSession IOC原理：工厂 + 反射 + 配置
此处使用工厂模式，一劳永逸 降低耦合
EntityManager
它是JPA中的持久化对象 封装所有的持久化方法，以及EntityTransaction
EntityTransaction
事务对象，目的是同化不同事物类型的差异，简便开发
JPA中的主键生成策略
IDENTITY
适用于数据库支持列的自增长情况 mysql db2(ibm)
SEQUENCE
适用于数据库支持序列的情况 Oracle db2
TABLE
用额外的一张表来维护你的主键
AUTO
默认就是Auto 默认使用Table
不完美：jpa提供的 主键生成策略 只限于 数值型
JPA的入门案例
配置文件(src下META-INF下persistence.xml 固定死的位置不能变)
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="myJpa" transaction-type="RESOURCE_LOCAL">
<properties>
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/test"/>
<property name="hibernate.connection.username" value="root"/>
<property name="hibernate.connection.password" value="root"/>
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
<property name="hibernate.show_sql" value="true"/>
<property name="hibernate.format_sql" value="true"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>
<property name="hibernate.connection.provider_class" value="org.hibernate.connection.C3P0ConnectionProvider"/>
properties>
persistence-unit>
persistence>
实体类
package com.itheima.domain;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
/**
* Title: Customer
* Description: 客户的实体类
* @author zhaocq
* @date 2018年9月18日
*/
@Entity
@Table(name="cst_customer")
public class Customer implements Serializable {
@Id
@Column(name="cust_id")
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Integer custId;
@Column(name="cust_name")
private String custName;
@Column(name="cust_source")
private String custSource;
@Column(name="cust_industry")
private String custIndustry;
@Column(name="cust_level")
private String custLevel;
@Column(name="cust_address")
private String custAddress;
@Column(name="cust_phone")
private String custPhone;
public Integer getCustId() {
return custId;
}
public void setCustId(Integer custId) {
this.custId = custId;
}
public String getCustName() {
return custName;
}
public void setCustName(String custName) {
this.custName = custName;
}
public String getCustSource() {
return custSource;
}
public void setCustSource(String custSource) {
this.custSource = custSource;
}
public String getCustIndustry() {
return custIndustry;
}
public void setCustIndustry(String custIndustry) {
this.custIndustry = custIndustry;
}
public String getCustLevel() {
return custLevel;
}
public void setCustLevel(String custLevel) {
this.custLevel = custLevel;
}
public String getCustAddress() {
return custAddress;
}
public void setCustAddress(String custAddress) {
this.custAddress = custAddress;
}
public String getCustPhone() {
return custPhone;
}
public void setCustPhone(String custPhone) {
this.custPhone = custPhone;
}
@Override
public String toString() {
return "Customer [custId=" + custId + ", custName=" + custName + ", custSource=" + custSource
+ ", custIndustry=" + custIndustry + ", custLevel=" + custLevel + ", custAddress=" + custAddress
+ ", custPhone=" + custPhone + "]";
}
}
测试Demo（DDL建表）
package com.itheima.test;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import org.junit.Test;
import domain.Customer;
public class JpaTest {
@Test
public void test() {
//创建entityManagerFactory工厂
EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("myJpa");
//获得EntityManager对象
EntityManager em = entityManagerFactory.createEntityManager();
//获取事物对象
EntityTransaction tx = em.getTransaction();
//开启事物
tx.begin();
Customer customer = new Customer();
customer.setCustName("hello jpa");
//保存操作
em.persist(customer);
//提交事物
tx.commit();
//关闭资源
em.close();
entityManagerFactory.close();
}
}
JPA的CRUD
抽取工具类
package utils;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
public class EntityManagerUtil {
private static EntityManagerFactory entityManagerFactory;
static {
entityManagerFactory=Persistence.createEntityManagerFactory("myJpa");
}
public EntityManager createEntityManager() {
return entityManagerFactory.createEntityManager();
}
}
增删改查方法
package com.itheima.test;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;
import javax.persistence.Query;
import org.junit.Test;
import domain.Customer;
import utils.EntityManagerUtil;
public class JpaCRUDTest {
//增
@Test
public void addTest() {
Customer customer = new Customer();
customer.setCustName("hello jpa3");
customer.setCustPhone("110");
EntityManager em = EntityManagerUtil.createEntityManager();
EntityTransaction tx = em.getTransaction();
tx.begin();
//增加persist方法
em.persist(customer);
tx.commit();
em.close();
}
//查
@Test
public void findTest() {
EntityManager em = EntityManagerUtil.createEntityManager();
EntityTransaction tx = em.getTransaction();
tx.begin();
//查询find方法
Customer c = em.find(Customer.class, 1);
System.out.println(c);
tx.commit();
em.close();
}
//改
@Test
public void updateTest() {
EntityManager em = EntityManagerUtil.createEntityManager();
EntityTransaction tx = em.getTransaction();
tx.begin();
//先查询
Customer c = em.find(Customer.class, 1);
//在用merge修改
c.setCustName("改名字了");
em.merge(c);
System.out.println(c);
tx.commit();
em.close();
}
//删
@Test
public void delTest() {
EntityManager em = EntityManagerUtil.createEntityManager();
EntityTransaction tx = em.getTransaction();
tx.begin();
//先查询
Customer c = em.find(Customer.class, 1);
//在用remove删除
em.remove(c);
tx.commit();
em.close();
}
//查询全部
@Test
public void findAllTest() {
EntityManager em = EntityManagerUtil.createEntityManager();
EntityTransaction tx = em.getTransaction();
tx.begin();
//查询find方法
Query query = em.createQuery("from Customer");// JPQL java persistence query language
List<Customer> resultList = query.getResultList();
for (Customer customer : resultList) {
System.out.println(customer);
}
tx.commit();
em.close();
}
//聚合函数
@Test
public void test() {
EntityManager em = EntityManagerUtil.createEntityManager();
EntityTransaction tx = em.getTransaction();
tx.begin();
//查询find方法
Query query = em.createQuery("select count(custId) from Customer");// JPQL java persistence query language
List<Customer> resultList = query.getResultList();
System.out.println(resultList.get(0));
tx.commit();
em.close();
}
}
JPA中的两种查询方式
Find和 getReference 的区别：
1. 加载时机不一样，find是立即加载，getReference是
延迟加载。
2. 返回的对象不一样，find返回的就是实体对象，
getReference返回的是代理对象。
Hibernate 的CRUD 练习
配置文件
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driverproperty>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/testproperty>
<property name="hibernate.connection.username">rootproperty>
<property name="hibernate.connection.password">adminproperty>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialectproperty>
<property name="hibernate.show_sql">trueproperty>
<property name="hibernate.format_sql">trueproperty>
<property name="hibernate.hbm2ddl.auto">updateproperty>
<property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProviderproperty>
<mapping class="com.itheima.domain.Customer"/>
session-factory>
hibernate-configuration>
抽取工具类
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
/**
* Title: HibernateUtil
* Description: Hibernate的工具类
* @author zhaocq
* @date 2018年9月18日
*/
public class HibernateUtil {
// private static EntityManagerFactory factory;
private static SessionFactory factory;
static{
// 创建工厂
// factory = Persistence.createEntityManagerFactory("myJpa");
// 创建Configuration对象
Configuration configuration = new Configuration();
configuration.configure();
factory = configuration.buildSessionFactory();
}
public static Session createSession(){
return factory.openSession();
}
}
CURD
package com.itheima.test;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;
import domain.Customer;
import utils.HibernateUtil;
/**
* Title: JpaTest
* Description:Hibernate的crud操作
* @author zhaocq
* @date 2018年9月18日
*/
public class HibernateCRUDTest {
/**
* Title: test
* Description: 保存
*/
@Test
public void test(){
Customer c = new Customer();
c.setCustName("hello Hibernate");
// 获取Session
Session session = HibernateUtil.createSession();
Transaction tx = session.beginTransaction();
// 执行保存操作
session.save(c);
// 提交事务
tx.commit();
// 关闭相关资源
session.close();
}
/**
* Title: test1
* Description: 根据ID查询
*/
@Test
public void test1(){
// 获取Session
Session session = HibernateUtil.createSession();
Transaction tx = session.beginTransaction();
// 执行保存操作
Customer c = session.get(Customer.class, 1);
System.out.println(c);
// 提交事务
tx.commit();
// 关闭相关资源
session.close();
}
/**
* Title: test2
* Description:更新
*/
@Test
public void test2(){
// 获取Session
Session session = HibernateUtil.createSession();
Transaction tx = session.beginTransaction();
// 执行保存操作
Customer c = session.get(Customer.class, 1);
c.setCustName("javaee520");
session.update(c);
// 提交事务
tx.commit();
// 关闭相关资源
session.close();
}
/**
* Title: test3
* Description: 删除
*/
@Test
public void test3(){
Customer c = new Customer();
c.setCustId(2);
// 获取Session
Session session = HibernateUtil.createSession();
Transaction tx = session.beginTransaction();
// 执行保存操作
//Customer c = session.get(Customer.class, 1);
session.delete(c);
// 提交事务
tx.commit();
// 关闭相关资源
session.close();
}
/**
* Title: test4
* Description: 查询全部
*/
@Test
public void test4(){
// 获取Session
Session session = HibernateUtil.createSession();
Transaction tx = session.beginTransaction();
// 创建Query
Query query = session.createQuery("from Customer");// HQL hibernate query language
List<Customer> list = query.list();
for(Customer l:list){
System.out.println(l);
}
// 提交事务
tx.commit();
// 关闭相关资源
session.close();
}
/**
* Title: test5
* Description: 聚合函数的使用
*/
@Test
public void test5(){
// 获取Session
Session session = HibernateUtil.createSession();
Transaction tx = session.beginTransaction();
// 创建Query
Query query = session.createQuery("select count(custId) from Customer");// JPQL java persistence query language
Object uniqueResult = query.uniqueResult();
System.out.println(uniqueResult);
// 提交事务
tx.commit();
// 关闭相关资源
session.close();
}
}