极简springboot+springdataJPA的使用，连接数据库

1、首先在springboot的基础上引入maven依赖：一个mysql的驱动，一个整合的JPA使用包

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.23</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-data-jpa -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
            <version>2.7.5</version>
        </dependency>

通过这篇博文，我才知道使用JPA只需要一个包就可以了

 SpringBoot_jpa 依赖引入_cnxjk的博客

2、配置yml，原来最最基本的springboot都不需要配置

server:
  port: 8888
spring:
  datasource:
    url: jdbc:mysql://192.168.0.120:3306/fossx?useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver

就这一点就好

3、写dao层：实体类和repository

@Entity
@Table(name = "clone_scan_pair2")
public class CloneScanPair {
    @Id
    @Column(name = "id")
    private String id;
    @Column(name = "group_id")
    private String groupId;
    @Column(name = "clone_scan_source")
    private String cloneScanSource;
    @Column(name = "clone_scan_match")
    private String cloneScanMatch;
    @Column(name = "task_id")
    private String taskId;

    public CloneScanPair() {
    }
    。。。。。。
}    

实体类一定要有无参构造方法，要不然会报一个No default constructor for entity的错，这是规定

@Repository
public interface CloneScanPairRepository extends JpaRepository<CloneScanPair,String> {
}

that's it

4、编写Start，一定要扫描包，获得组件 

@SpringBootApplication
@ComponentScan("com.nbkj.fossx.engine.repository")
@ComponentScan("com.nbkj.fossx.engine")
public class Start {
    public static void main(String[] args) {
        SpringApplication.run(Start.class,args);
    }
}

当你没有启动springboot，是无法通过autowire和resource获得bean的