Question

我正在尝试编写一个自动重试事务＆＃34; monkey patch＆＃34;光滑的（1.0，不幸的是）。此外，我希望它只重试某些类型的异常。不幸的是，我一直在运行类型擦除的问题。根据我的理解，我想要做的是最终混合运行时和编译时成语，但在这一点上，我所有的想法。我尝试使用反射吗？

object SessionSupport {

  /**
   * Patches the session object to add trnansaction serializable
   * with automatic retry
   */
  implicit class SlickSessionWrapper(session:Session) {
    private val logger = LoggerFactory.getLogger(getClass)

    val MAX_RETRIES = 3
    // UNFORTUNATELY I CANT SEEM TO GET RID OF THE UNCHECKED WARNING.
    // As such, the type check is alwasy going to "pass" for ANY throwable
    def withRetryingSerializableTransaction[A, T <: Throwable ](f: => A)(implicit retryCt:Int = 0):A = {
      val res:Try[A] = session.withTransaction {
        session.conn.setTransactionIsolation(
          java.sql.Connection.TRANSACTION_SERIALIZABLE
        )

        Try(f)
      }

      res match {
        case Success(v) => v
        case Failure(thr) => {
          if(thr.isInstanceOf[T] && retryCt < MAX_RETRIES) {  // type erasure here!!!
            logger.debug(s"Caught ${thr.toString}, retrying")
            withRetryingSerializableTransaction[A, T](f)(retryCt + 1)
          } else {
            logger.error(s"Caught ${thr.toString}.  Rethrowing", thr)
            throw thr
          }
        }
      }
    }
  }
}

Answer 1

是的，你需要对此进行反思。将声明更改为

def withRetryingSerializableTransaction[A, T <: Throwable : Manifest]

然后代替thr.isInstanceOf[T]，执行manifest.runtimeClass.isInstance(thr)

如何在具有更高阶函数的隐式类中删除未经检查的警告

1 个答案: