JPA基础思路

这里分享一个小编自学的JAP基础

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.test.jpa.helloworld.Customer</class>
<properties>
<!-- 连接数据库的基本信息 -->
<property name="javax.persistence.jdbc.driver" value="oracle.jdbc.driver.OracleDriver"/>
<property name="javax.persistence.jdbc.url" value="jdbc:oracle:thin:@localhost:1521:orcl"/>
<property name="javax.persistence.jdbc.user" value="jpa"/>
<property name="javax.persistence.jdbc.password" value="orcl"/>

<!-- 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"/>
<!-- 反向生成数据库 -->
<property name="hibernate.hbm2ddl.auto" value="update"/>


</properties> 
</persistence-unit>
</persistence>

Customer 实体类

package com.test.jpa.helloworld;


import java.util.Date;


import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;


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


private Integer id;
private String lastName;


private String email;
private int age;

private Date createdTime;

private Date birth;
@GeneratedValue(strategy=GenerationType.AUTO)
@Id
public Integer getId() {
return id;
}


public void setId(Integer id) {
this.id = id;
}


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 int getAge() {
return age;
}


public void setAge(int age) {
this.age = age;
}




//精确都时分秒
@Temporal(TemporalType.TIMESTAMP)
public Date getCreatedTime() {
return createdTime;
}


public void setCreatedTime(Date createdTime) {
this.createdTime = createdTime;
}


//精确到日期
@Temporal(TemporalType.DATE)
public Date getBirth() {
return birth;
}


public void setBirth(Date birth) {
this.birth = birth;
}


@Transient
public String getInfo(){
return "工具方法不需要添加到数据库中，加注解--Transient";
}


@Override
public String toString() {
return "Customer [id=" + id + ", lastName=" + lastName + ", email="
+ email + ", age=" + age + ", createdTime=" + createdTime
+ ", birth=" + birth + "]";
}



}

main类

main方法

package com.test.jpa.helloworld;


import java.util.Date;


import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;


public class Main {


public static void main(String[] args) {


// 1.创建EntityManagerFatory  是配置文件的name属性
String persistenceUnitName = "jpa-1";
EntityManagerFactory entityManagerFatory = Persistence
.createEntityManagerFactory(persistenceUnitName);


// 2.创建EntityManager
EntityManager entityManager = entityManagerFatory.createEntityManager();


// 3.开启事物
EntityTransaction transaction = entityManager.getTransaction();
transaction.begin();
// 4.持久化操作
Customer customer = new Customer();
customer.setAge(12);
customer.setEmail("mail.qq.com");
customer.setLastName("zhangsan");
customer.setBirth(new Date());
customer.setCreatedTime(new Date());
entityManager.persist(customer);
// 5.提交事物
transaction.commit();


// 6.关闭EntityManager
entityManager.close();
// 7.关闭EntityManagerFatory
entityManagerFatory.close();
}
}