JPA入门

persistence.xml:

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
	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">
	<persistence-unit name="jpa-1" transaction-type="RESOURCE_LOCAL">
		<!-- 
		配置使用什么 ORM 产品来作为 JPA 的实现 
		1. 实际上配置的是  javax.persistence.spi.PersistenceProvider 接口的实现类
		2. 若 JPA 项目中只有一个 JPA 的实现产品, 则也可以不配置该节点. 
		-->
		<provider>org.hibernate.ejb.HibernatePersistence</provider>
	
		<!-- 添加持久化类 -->
		<class>com.ldp.jpa.bean.Customer</class>
		<!-- 
		配置二级缓存的策略 
		ALL：所有的实体类都被缓存
		NONE：所有的实体类都不被缓存. 
		ENABLE_SELECTIVE：标识 @Cacheable(true) 注解的实体类将被缓存
		DISABLE_SELECTIVE：缓存除标识 @Cacheable(false) 以外的所有实体类
		UNSPECIFIED：默认值，JPA 产品默认值将被使用
		-->
		<shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode>
	
		<properties>
			<!-- 连接数据库的基本信息 -->
			<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
			<property name="javax.persistence.jdbc.url" value="jdbc:mysql:///20190429jpa"/>
			<property name="javax.persistence.jdbc.user" value="root"/>
			<property name="javax.persistence.jdbc.password" value="123456"/>
			
			<!-- 配置 JPA 实现产品的基本属性. 配置 hibernate 的基本属性 -->
			<property name="hibernate.format_sql" value="true"/>
			<property name="hibernate.show_sql" value="true"/>
			<property name="hibernate.hbm2ddl.auto" value="update"/>
		</properties>
	</persistence-unit>
</persistence>

Customer实体类

package com.ldp.jpa.bean;
//定义一个持久化类

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

import org.hibernate.type.descriptor.java.PrimitiveByteArrayTypeDescriptor;

@Table(name="customer")
@Entity
public class Customer {

	private Integer id;
	private String lastName;
	private String email;
	private Integer age;
	
	@GeneratedValue(strategy=GenerationType.AUTO)
	@Id
	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 String getEmail() {
		return email;
	}
	public void setEmail(String email) {
		this.email = email;
	}
	public Integer getAge() {
		return age;
	}
	public void setAge(Integer age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return "Customer [id=" + id + ", lastName=" + lastName + ", email=" + email + ", age=" + age + "]";
	}
}

测试JPA的操作步骤：

@Test
	public void test01() {
		//操作步骤JPA
		//1.创建EntityManagerFactory
		String persistenceUnitName="jpa-1";
		EntityManagerFactory entityManagerFactory=
				Persistence.createEntityManagerFactory(persistenceUnitName);
		//2.获取EntityManager对象
		EntityManager entityManager = entityManagerFactory.createEntityManager();
		//3.开启事务
		EntityTransaction transaction = entityManager.getTransaction();
		transaction.begin();
		//4.进行持久化操作
		Customer customer=new Customer();
		customer.setAge(22);
		customer.setEmail("[email protected]");
		customer.setLastName("刘东平");
		entityManager.persist(customer);
		//5.提交事务
		transaction.commit();
		//6.关闭entitymanager对象
		entityManager.close();
		//7.关闭entitymanagerfactory对象
		entityManagerFactory.close();
		
	}