（1）Transactional标注在DBServiceImpl 类上的updateMediaInfo方法。
（2）DBServiceImpl 类同样定义了一个切面类DynamicDataSourceAspectJ，
对DBServiceImpl 类上的所有方法都进行AOP操作。
（3）transactional与DynamicDataSourceAspectJ执行的先后顺序是咋样的呀？（我代码测试发现是会先执行transactional，但是代码原理我不知道，哭泣中）

@Service("idbService")
public class DBServiceImpl implements IDBService {
    private MediaInfoDao mediaInfoDao;

    @Autowired
    public DBServiceImpl(MediaInfoDao mediaInfoDao) {
        this.mediaInfoDao = mediaInfoDao;
    }

    @Override
    public List<Map<String, Object>> listMediaInfo(String dbSeq, String tbName, String fastdfsUrl) {
        List<Map<String, Object>> result = mediaInfoDao.listMediaInfo(tbName, fastdfsUrl);
        return result;
    }

    @Transactional
    @Override
    public void updateMediaInfo(String dbSeq, String tbName, Long id, String fastdfsUrl, String fastdfsUrlValue) {
        mediaInfoDao.updateMediaInfo(tbName, id, fastdfsUrl, fastdfsUrlValue);
    }
}

@Aspect
@Component
public class DynamicDataSourceAspectJ {
    @Pointcut("execution(*  com.sunt.ossasync.service.impl.DBServiceImpl.*(..))")
    public void plugin() {
    }

    @Before("plugin()")
    public void before(JoinPoint joinPoint) {
        System.out.println("进行before拦截 " + joinPoint);
        Object[] args = joinPoint.getArgs(); // 参数值
        String dataSource = "datasource" + args[0];
        DataSourceHolder.setDataSource(dataSource);
    }

    @After("plugin()")
    public void after(JoinPoint joinPoint) {
        System.out.println("进行after拦截 " + joinPoint);
    }

    @AfterReturning(pointcut = "plugin()", returning = "returnValue")
    public void afterReturning(JoinPoint joinPoint, Object returnValue) {
        System.out.println("进行return拦截  " + joinPoint + "，返回值[" + returnValue + "]");
    }

}