JPA系列二：基本使用

小灰灰 2022-02-09 09:51 298阅读 0赞

1、创建jpa项目  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3_size_16_color_FFFFFF_t_70]  
2、添加maven模块  
![!\[][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3_size_16_color_FFFFFF_t_70 1]  
3、删除lib文件夹。将META-INF移到resources里面。  
![在这里插入图片描述][2019050213055044.png]  
4、引入依赖

<dependencies>
        
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>4.2.4.Final</version>
        </dependency>
        
        <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">
         
         <provider>org.hibernate.ejb.HibernatePersistence</provider>
    
         
         <class>com.atguigu.jpa.helloworld.Customer</class>
    
         <properties>
             
             <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"/>
    
             
             <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("tom@atguigu.com");
    	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：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3_size_16_color_FFFFFF_t_70 2]  
测试成功后会在数据库自动创建表jpa\_cutomers。并插入数据  
![在这里插入图片描述][20190502131826628.png]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3_size_16_color_FFFFFF_t_70]: /images/20220206/aab2adadbbb74b65acbc49f01095ead0.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/2019050220202135.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3,size_16,color_FFFFFF,t_70
[2019050213055044.png]: /images/20220206/8ed293cb3b1a4f7a8ef534e335adc9ce.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3_size_16_color_FFFFFF_t_70 2]: /images/20220206/062980f92cd04e259d85bd16f6390890.png
[20190502131826628.png]: /images/20220206/e142a37b376a466192d8bc008c408af2.png