Class MessageHandler<TContent>Abstract

constructor

• new MessageHandler<TContent>(messageType, overrides?, middleware?): MessageHandler<TContent>

• The MessageHandler constructor

  Type Parameters

  • TContent

  Parameters

  • messageType: string

    The type of the message which this MessageHandler handles.

  • Optional overrides: SubscriptionConfig

    Custom adjustments to overwrite Rascal subscription configuration settings.

  • middleware: OnMessageMiddleware<unknown>[] = []

    Middleware functions that should be executed for this specific message handler in addition to the global ones.

  Returns MessageHandler<TContent>

Readonly messageType

Readonly middleware

Optional Readonly overrides

Optional mapError

• mapError(error): Error

• Function to map thrown error of unspecified type to a more human-readable error. Defining this mapping function eliminates the need to wrap onMessage contents into an explicit try-catch block.

  Parameters

  • error: unknown

  Returns Error

Abstract onMessage

• onMessage(payload, message, ackOrNack): Promise<void>

• Main message handling function.

  Parameters

  • payload: TContent

    non-binary message payload (usually a json)

  • message: MessageInfo<TContent>

    message with all related message metadata, including message envelope

  • ackOrNack: AckOrNack

    acknowledgment or rejection callback that can be called to forcefully complete the message processing.

  Returns Promise<void>

Optional onMessageFailure

• onMessageFailure(payload, message, error): Promise<void>

• Function that will be called after the last retry attempt has failed. Useful for handling errors in an explicit way.

  Parameters

  • payload: TContent

    non-binary message payload (usually a json)

  • message: MessageInfo<TContent>

    message with all related message metadata, including message envelope

  • error: Error

    error object that caused message processing to repeatedly fail

  Returns Promise<void>