JPA系列二：基本使用

1、创建jpa项目

2、添加maven模块

3、删除lib文件夹。将META-INF移到resources里面。

4、引入依赖

<dependencies>
    <!--  hibernate 依赖 -->
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>4.2.4.Final</version>
    </dependency>
    <!-- mysql 驱动 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.17</version>
    </dependency>
</dependencies>

5、创建实体类Customer

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

	private Integer id;
	private String lastName;
	private String email;
	private int age;
	
	public Customer() {
		// TODO Auto-generated constructor stub
	}
	
	public Customer(String lastName, int age) {
		super();
		this.lastName = lastName;
		this.age = 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 int getAge() {
		return age;
	}

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

6、在persistence.xml中配置

 <persistence-unit name="NewPersistenceUnit">
     <!--
      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.atguigu.jpa.helloworld.Customer</class>

     <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://localhost:3306/jpa"/>
         <property name="javax.persistence.jdbc.user" value="root"/>
         <property name="javax.persistence.jdbc.password" value="root"/>

         <!-- 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>

7、编写方法测试

public static void main(String[] args) {
	//1. 创建 EntitymanagerFactory
	String persistenceUnitName = "NewPersistenceUnit";
	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("[email protected]");
	customer.setLastName("Tom");
	entityManager.persist(customer);

	//5. 提交事务
	transaction.commit();
	
	//6. 关闭 EntityManager
	entityManager.close();
	
	//7. 关闭 EntityManagerFactory
	entityManagerFactory.close();
}

控制台输出：

测试成功后会在数据库自动创建表jpa_cutomers。并插入数据