JPA入门级demo

下面来实现一个简单的 jpa工程（入门级工程，仅供了解使用）

1、在eclipse中创建jpa工程（平时都用idea,回过头来用eclipse真是郁闷到死啊！）

2、引入jar包就不多说了

3、编写persistence.xml文件

<?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，则也可以不配置该阶段
         -->
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        
        
        <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:///jpa"/>
            <property name="javax.persistence.jdbc.user" value="root"/>
            <property name="javax.persistence.jdbc.password" value="houchen"/>
            
            <!-- 配置JPA 实现产品的基本属性，也就是配置hibernate的基本属性  -->
            <property name="hibernate.format_sql" value="true"/>
            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.hbm2ddl.auoto" value="update"/>
        </properties>
    </persistence-unit>
</persistence>

4、创建实体类并在persistence.xml中添加要持久化的类

//进行映射的表的名称
@Table(name="JPA_CUTOMERS")
@Entity
public class Customer {

    private Integer id;
    private String lastName;

    private String email;
    private int age;
    
    

    //生成主键的方式
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Id
    public Integer getId() {
        return id;
    }

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

    @Column(name="LAST_NAME",length=50,nullable=false)
    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;
    }
    
}

<!-- 添加持久化类 -->

<class>com.atguigu.jpa.helloworld.Customer</class>

5、进行持久化的测试操作

public class Main {
    
    public static void main(String[] args) {
        //1、创建EntitymanagerFactory
        String persistenceUnitName ="jpa-1";
        EntityManagerFactory entityManagerFactory = Persistence.
                createEntityManagerFactory(persistenceUnitName);
        
        //2、创建EntityManager
        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(12);
        customer.setEmail("1285653662@qq.com");
        customer.setLastName("chen");
        
        entityManager.persist(customer);
        
        //5、提交事务
        transaction.commit();
        
        //6、关闭entityManager
        entityManager.close();
        
        //7、关闭entityManagerFactory
        entityManagerFactory.close();
        
    }
    
}