使用ssm框架，配置多数据源自动切换

SpringBoot 版本 2.0.3

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.3.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

已经引入了 postgreSQL 和 mysql 的链接库

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <scope>runtime</scope>
</dependency>

使用 druid 连接池和 mybatis plus 插件

1. 在配置文件中配置了多个数据源

   spring:
     datasource:
       multiple:
         db1:
           username: postgres
           password: postgres
           driverClassName: org.postgresql.Driver
           url: jdbc:postgresql://localhost:5432/data_a
           initialSize: 5
           minIdle: 5
           maxActive: 20
         db2:
           username: root
           password: root
           driver-class-name: com.mysql.jdbc.Driver
           url: jdbc:mysql:///data_b
           initialSize: 5
           minIdle: 5
           maxActive: 20

2. 然后在 MyBatiesPlusConfiguration 中注入

   @Bean(name = "db1")
   @ConfigurationProperties(prefix = "spring.datasource.multiple.db1" )
   public DataSource db1() {
       return DruidDataSourceBuilder.create().build();
   }
   
   @Bean(name = "db2")
   @ConfigurationProperties(prefix = "spring.datasource.multiple.db2" )
   public DataSource db2() {
       return DruidDataSourceBuilder.create().build();
   }

3. 添加到multipleDataSource中

   /**
    * 动态数据源配置
    * @return
    */
   @Bean
   @Primary
   public DataSource multipleDataSource(@Qualifier("db1") DataSource db1, @Qualifier("db2") DataSource db2) {
       MultipleDataSource multipleDataSource = new MultipleDataSource();
       Map< Object, Object > targetDataSources = new HashMap<>();
       targetDataSources.put(DataSourceEnum.DB1.getValue(), db1);
       targetDataSources.put(DataSourceEnum.DB2.getValue(), db2);
       //添加数据源
       multipleDataSource.setTargetDataSources(targetDataSources);
       //设置默认数据源
       multipleDataSource.setDefaultTargetDataSource(db1);
       return multipleDataSource;
   }

4. 如果需要切换数据源，则在指定的方法上加上@DataSource注解即可

@Override
@DataSource(DataSourceEnum.DB2)
public List<Student> selectList(Wrapper<Student> wrapper) {
    return super.selectList(wrapper);
}