DataSourceAutoConfiguration分析

SpringBoot有一个自动配置DataSourceAutoConfiguration 为数据源配置
/META-INF/spring.factories文件找到DataSourceAutoConfiguration配置类
一、先来看下DataSourceAutoConfiguration配置类生效的时机，观察源码发现

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })
@EnableConfigurationProperties(DataSourceProperties.class)
@Import({ DataSourcePoolMetadataProvidersConfiguration.class, DataSourceInitializationConfiguration.class })

在springboot下只有EmbeddedDatabaseType类型是爆红，说明没有相关依赖引入,而它属于spring-jdbc依赖，那么加上(从spring-boot-starter-data-jdbc里面复制的)

<dependency><groupId>org.springframework</groupId><artifactId>spring-jdbc</artifactId><version>5.2.1.RELEASE</version><scope>compile</scope>
</dependency>

此时重启项目发现容器中已经有org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration 即此时DataSourceAutoConfiguration生效，但是它仅仅是DataSourceAutoConfiguration这个类被注入容器，要想自动配置数据源
还需要让EmbeddedDatabaseConfiguration或PooledDataSourceConfiguration生效

当引入下面依赖时可以去掉spring-jdb因为spring-boot-starter-data-jdbc里面引入了spring-jdb依赖

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jdbc</artifactId>
</dependency>

DataSourceAutoConfiguration 就会触发自动配置
配置生效时机参考传送门

题外话spring-boot-starter-jdbc 和 spring-boot-starter-data-jdbc 的区别
一、你会发现spring-boot-starter-data-jdbc 依赖下面有spring-boot-starter-jdbc和spring-data-jdbc
而spring-data-jdbc引入了spring-data-commons 其中CrudRepository接口提供了基础增删改查，该接口就在spring-data-commons中。

二、springboot默认的数据源是HikariDataSource，HikariCP依赖位于spring-boot-starter-jdbc下。
上面测试用到的
依赖

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><version>2.2.1.RELEASE</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jdbc</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.24</version></dependency></dependencies>

测试类MyBatisPlusBootMain

@SpringBootApplication
public class MyBatisPlusBootMain implements CommandLineRunner, ApplicationContextAware {Logger logger = LoggerFactory.getLogger(MyBatisPlusBootMain.class);@Autowired(required = false)DataSource dataSource;private  ApplicationContext applicationContext;public static void main(String[] args) {ApplicationContext run = SpringApplication.run(MyBatisPlusBootMain.class, args);UsersEntity user01 = run.getBean("user01", UsersEntity.class);System.out.println(user01);DataSourceAutoConfiguration dataSourceAutoConfiguration = run.getBean("org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration", DataSourceAutoConfiguration.class);System.out.println(dataSourceAutoConfiguration);}@Overridepublic void run(String... args) throws Exception {System.out.println(">>>>>>>>>>>>>>>>>服务启动执行");showConnection();showIOCBean();}private void showIOCBean() {String[] names = this.applicationContext.getBeanDefinitionNames();for (int i = 0; i < names.length; i++) {System.out.println(names[i]);}}private void showConnection() throws SQLException {logger.info("dataSource:{}", dataSource.getClass().getName());Connection connection = dataSource.getConnection();logger.info("connection:{}", connection.toString());}@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {this.applicationContext=applicationContext;}
}

yml

spring:datasource:url: jdbc:mysql://localhost:3306/testusername: rootpassword: 3306

更换默认的数据源改为DruidDataSource

参考：传送门

方法一：

添加依赖

<dependency><groupId>com.alibaba</groupId><artifactId>druid</artifactId><version>1.1.23</version>
</dependency>

yml

spring:datasource:url: jdbc:mysql://localhost:3306/bms_testusername: rootpassword: 3306type: com.alibaba.druid.pool.DruidDataSource

此时数据源更改为DruidDataSource

方法二：

1 、添加druid依赖
2、创建DataSource的bean，进行相关配置后，返回DruidDataSource

@Beanpublic DataSource dataSource() {DruidDataSource dataSource = new DruidDataSource();dataSource.setUrl("jdbc:mysql://localhost:3306/bms_test");dataSource.setUsername("root");dataSource.setPassword("3306");return dataSource;}

多数据源配置