JPA--环境搭建

约定不等于承诺〃 2021-08-14 01:47 372阅读 0赞

### JPA环境搭建 ###

创建Maven工程并导入依赖

<?xml version="1.0" encoding="UTF-8"?>

4.0.0

<groupId>pers.zhang</groupId>
    <artifactId>JPA_Pro</artifactId>
    <version>1.0-SNAPSHOT</version>
    
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.hibernate.version>5.0.7.Final</project.hibernate.version>
    </properties>
    
    <dependencies>
        
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    
        
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>${project.hibernate.version}</version>
        </dependency>
    
        
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-c3p0</artifactId>
            <version>${project.hibernate.version}</version>
        </dependency>
    
        
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    
        
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
    </dependencies>

\`\`\`

配置jpa的核心配置文件

*  位置：类路径下的一个叫做 META-INF 的文件夹下
 *  文件名：persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
    <persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0">
        
        <persistence-unit name="myJpa" transaction-type="RESOURCE_LOCAL">
            
            <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
    
            
            <properties>
                
                <property name="javax.persistence.jdbc.user" value="root"/>
                <property name="javax.persistence.jdbc.password" value="123456"/>
                <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
                <property name="javax.persistence.jdbc.url" value="jdbc:mysql:///chapter05"/>
    
                
                
                <property name="hibernate.show_sql" value="true"/>
                
                <property name="hibernate.hbm2ddl.auto" value="create"/>
    
            </properties>
        </persistence-unit>
    </persistence>

使用IDEA添加数据源  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NvbGRfX19wbGF5_size_16_color_FFFFFF_t_70]  
注意：关联mysql失败\_Server returns invalid timezone. Go to ‘Advanced’ tab and set ‘serverTimezon’

解决方案：MySQL默认的时区是UTC时区，比北京时间晚8个小时，所以要修改mysql的时长。

在mysql的命令模式下，输入：

set global time_zone='+8:00';

编写实体类并关联表

package pers.zhang.domain;
    
    /** * @author zhang * @date 2019/12/14 - 20:17 */
    
    import javax.persistence.*;
    
    /** * 配置映射关系 * 1.实体类和表的映射关系 * @Entity:声明实体类 * @Table：配置实体类和表的映射关系 * name:配置数据库表的名称 * 2.实体类中属性和表中字段的映射关系 * * */
    @Entity
    @Table(name = "cst_customer")
    public class Customer { 
    
        /* @Id：配置主键 @GeneratedValue：配置主键的生成策略 GenerationType.IDENTITY：自增 @Column：配置属性和字段的映射关系 name：表中字段名 */
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        @Column(name = "cust_id")
        private Long custId;//客户主键
    
        @Column(name = "cust_name")
        private String custName;//客户名称
    
        @Column(name = "cust_source")
        private String custSource;//客户来源
    
        @Column(name = "cust_industry")
        private String custIndustry;//客户所属行业
    
        @Column(name = "cust_level")
        private String custLevel;//客户级别
    
        @Column(name = "cust_address")
        private String custAddress;//客户地址
    
        @Column(name = "cust_phone")
        private String custPhone;//客户电话
    
        public Long getCustId() { 
            return custId;
        }
    
        public void setCustId(Long custId) { 
            this.custId = custId;
        }
    
        public String getCustName() { 
            return custName;
        }
    
        public void setCustName(String custName) { 
            this.custName = custName;
        }
    
        public String getCustSource() { 
            return custSource;
        }
    
        public void setCustSource(String custSource) { 
            this.custSource = custSource;
        }
    
        public String getCustIndustry() { 
            return custIndustry;
        }
    
        public void setCustIndustry(String custIndustry) { 
            this.custIndustry = custIndustry;
        }
    
        public String getCustLevel() { 
            return custLevel;
        }
    
        public void setCustLevel(String custLevel) { 
            this.custLevel = custLevel;
        }
    
        public String getCustAddress() { 
            return custAddress;
        }
    
        public void setCustAddress(String custAddress) { 
            this.custAddress = custAddress;
        }
    
        public String getCustPhone() { 
            return custPhone;
        }
    
        public void setCustPhone(String custPhone) { 
            this.custPhone = custPhone;
        }
    
        @Override
        public String toString() { 
            return "Customer{" +
                    "custId=" + custId +
                    ", custName='" + custName + '\'' +
                    ", custSource='" + custSource + '\'' +
                    ", custIndustry='" + custIndustry + '\'' +
                    ", custLevel='" + custLevel + '\'' +
                    ", custAddress='" + custAddress + '\'' +
                    ", custPhone='" + custPhone + '\'' +
                    '}';
        }
    }

测试：

package pers.zhang.test;
    
    import org.junit.Test;
    import pers.zhang.domain.Customer;
    
    import javax.persistence.EntityManager;
    import javax.persistence.EntityManagerFactory;
    import javax.persistence.EntityTransaction;
    import javax.persistence.Persistence;
    
    /** * @author zhang * @date 2019/12/14 - 20:31 */
    public class JpaTest { 
    
        /* JPA的操作步骤： 1.加载配置文件创建工厂对象（实体管理类工厂） 2.通过实体管理类工厂获取实体管理器 3.获取事务对象，开启事务 4.进行CRUD 5.提交事务或回滚事务 6.释放资源 */
        @Test
        public void saveTest(){ 
            //1.加载配置文件创建工厂对象（实体管理类工厂）
            EntityManagerFactory factory = Persistence.createEntityManagerFactory("myJpa");
            //2.通过实体管理类工厂获取实体管理器
            EntityManager entityManager = factory.createEntityManager();
            //3.获取事务对象，开启事务
            EntityTransaction transaction = entityManager.getTransaction();
            transaction.begin();
            //4.进行CRUD
            Customer customer = new Customer();
            customer.setCustName("阿里巴巴");
            customer.setCustIndustry("电商");
            //保存
            entityManager.persist(customer);
            //5.提交事务或回滚事务
            transaction.commit();
            //6.释放资源
            entityManager.close();
            factory.close();
    
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NvbGRfX19wbGF5_size_16_color_FFFFFF_t_70 1]  
后台输出：

Hibernate: drop table if exists cst_customer
    Hibernate: create table cst_customer (cust_id bigint not null auto_increment, cust_address varchar(255), cust_industry varchar(255), cust_level varchar(255), cust_name varchar(255), cust_phone varchar(255), cust_source varchar(255), primary key (cust_id))
    Hibernate: insert into cst_customer (cust_address, cust_industry, cust_level, cust_name, cust_phone, cust_source) values (?, ?, ?, ?, ?, ?)

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