//设置package包名称以及导入依赖的类
package com.twitter.finagle.thrift

import com.twitter.finagle.{Service, SimpleFilter}
import com.twitter.io.Buf
import com.twitter.util.Future
import org.apache.thrift.{TApplicationException, TException}
import org.apache.thrift.protocol.{TMessage, TMessageType, TProtocolFactory}

private[finagle] object UncaughtAppExceptionFilter {

  
  def writeExceptionMessage(
    thriftRequest: Buf,
    throwable: Throwable,
    protocolFactory: TProtocolFactory
  ): Buf = {
    val reqBytes = Buf.ByteArray.Owned.extract(thriftRequest)
    // NB! This is technically incorrect for one-way calls,
    // but we have no way of knowing it here. We may
    // consider simply not supporting one-way calls at all.
    val msg = InputBuffer.readMessageBegin(reqBytes, protocolFactory)
    val name = msg.name

    val buffer = new OutputBuffer(protocolFactory)
    buffer().writeMessageBegin(
      new TMessage(name, TMessageType.EXCEPTION, msg.seqid))

    // Note: The wire contents of the exception message differ from Apache's Thrift in that here,
    // e.toString is appended to the error message.
    val x = new TApplicationException(
      TApplicationException.INTERNAL_ERROR,
      s"Internal error processing $name: '$throwable'")

    x.write(buffer())
    buffer().writeMessageEnd()
    Buf.ByteArray.Owned(buffer.toArray)
  }

}

private[finagle] class UncaughtAppExceptionFilter(protocolFactory: TProtocolFactory)
  extends SimpleFilter[Array[Byte], Array[Byte]]
{
  import UncaughtAppExceptionFilter.writeExceptionMessage

  def apply(
    request: Array[Byte],
    service: Service[Array[Byte], Array[Byte]]
  ): Future[Array[Byte]] =
    service(request).handle {
      case e if !e.isInstanceOf[TException] =>
        val buf = Buf.ByteArray.Owned(request)
        val msg = writeExceptionMessage(buf, e, protocolFactory)
        Buf.ByteArray.Owned.extract(msg)
    }
}