映射策略

实体和数据库表的映射方式有两种：

1. XML文件
2. 注解

XML文件相对来讲比较笨重，不易重构，我们选择注解形式。实体上的直接注解违反了单一职责的原则，所以我们引入DTO。

package com.lugew.springbootddd;
import lombok.Getter;
import lombok.Setter;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
/**
 * @author 夏露桂
 * @since 2021/6/10 12:00
 */
@Getter
@Setter
@Entity
public class SnackMachineDto {
    @Id
    @GeneratedValue
    private long id;
    private int oneCentCount;
    private int tenCentCount;
    private int quarterCount;
    private int oneDollarCount;
    private int fiveDollarCount;
    private int twentyDollarCount;
    private float moneyInTransaction;
}

同时配置文件设置：

server:
  port: 23333
spring:
  h2:
    console:
      enabled: true
  datasource:
    url: jdbc:h2:mem:testdb
    driverClassName: org.h2.Driver
    username: sa
    password:
  jpa:
    database-platform: org.hibernate.dialect.H2Dialect
logging:
  level:
    org:
      hibernate:
        SQL: debug
        type:
          descriptor:
            sql: trace

启动项目，访问http://localhost:23333/h2-console

最后，我们执行SQL，插入数据：

insert into snack_machine_dto (five_dollar_count, money_in_transaction,one_cent_count, one_dollar_count,quarter_count, ten_cent_count, twenty_dollar_count, id) values (1, 0.0, 1, 1, 1, 1, 1, 1);

为了避免每次重启都要执行sql，我们为Spring boot配置自动执行：

server:
  port: 23333
spring:
  h2:
    console:
      enabled: true
  datasource:
    data: classpath:sql/init.sql
    url: jdbc:h2:mem:testdb;MODE=MYSQL
    driverClassName: org.h2.Driver
    username: sa
    password:
  jpa:
    database-platform: org.hibernate.dialect.H2Dialect
logging:
  level:
    org:
      hibernate:
        SQL: debug
        type:
          descriptor:
            sql: trace