@wangyanrui 是不太懂，但是为啥我换了个写法就能读取到了呢？

@Configuration
@PropertySource(value= "classpath:application-ds.yml",factory = PropertySourceConfig.class)
@EnableConfigurationProperties
public class TransactionConfig {


@Bean
@ConfigurationProperties(prefix = "ds2")
public DataSource dataSource() {
return DataSourceBuilder.create().build();
}

}