Package org.axonframework.messaging.core

Interface MessageStream.Single<M extends Message>

Type Parameters:
M - The type of Message contained in the singular MessageStream.Entry of this stream.
All Superinterfaces:
MessageStream<M>
All Known Subinterfaces:
MessageStream.Empty<M>
Enclosing interface:
MessageStream<M extends Message>
public static interface MessageStream.Single<M extends Message> extends MessageStream<M>
A MessageStream implementation that returns at most a single result before completing.
Since:
5.0.0
Author:
Allard Buijze, Mateusz Nowak, Mitchell Herrijgers, Steven van Beelen
See Also:

  • Method Details

    • first

      default MessageStream.Single<M> first()
      Description copied from interface: MessageStream
      Returns a stream that includes only the first message of this stream, unless it completes without delivering any messages, in which case it completes the same way.

      When the first message is delivered, the returned stream completes normally, independently of how this stream completes. Upon consuming the first message, this stream is MessageStream.close() immediately.

      Specified by:
      first in interface MessageStream<M extends Message>
      Returns:
      A stream that includes only the first message of this stream.

    • map

      default <RM extends Message> MessageStream.Single<RM> map(Function<MessageStream.Entry<M>,MessageStream.Entry<RM>> mapper)
      Description copied from interface: MessageStream
      Returns a stream that maps each entry from this stream using given mapper function into an entry carrying a MessageEntry with a Message of type RM.

      The returned stream completes the same way this stream completes.

      Specified by:
      map in interface MessageStream<M extends Message>
      Type Parameters:
      RM - The declared type of Message contained in the returned entry.
      Parameters:
      mapper - The function converting entries from this stream from entries containing message of type M to RM.
      Returns:
      A stream with all entries mapped according to the mapper function.

    • mapMessage

      default <RM extends Message> MessageStream.Single<RM> mapMessage(Function<M,RM> mapper)
      Description copied from interface: MessageStream
      Returns a stream that maps each message from the entries in this stream using the given mapper function. This maps the Messages from type M to type RM.

      The returned stream completes the same way this stream completes.

      Specified by:
      mapMessage in interface MessageStream<M extends Message>
      Type Parameters:
      RM - The declared type of Message contained in the returned entry.
      Parameters:
      mapper - The function converting message from the entries in this stream from type M to RM.
      Returns:
      A stream with all entries mapped according to the mapper function.

    • filter

      default MessageStream.Single<M> filter(Predicate<MessageStream.Entry<M>> filter)
      Description copied from interface: MessageStream
      Returns a stream that will filter entries based on the given filter.
      Specified by:
      filter in interface MessageStream<M extends Message>
      Parameters:
      filter - The MessageStream.Entry predicate, that will filter out entries. Returning true from this lambda will keep the entry, while returning false will remove it.
      Returns:
      A stream for which the entries have been filtered by the given filter.

    • onNext

      default MessageStream.Single<M> onNext(Consumer<MessageStream.Entry<M>> onNext)
      Description copied from interface: MessageStream
      Invokes the given onNext each time an entry is consumed from this stream.

      Depending on the stream's implementation, the function may be invoked when the entry is provided to the Consumer, or at the moment it's available for reading on the stream. Subscribing multiple times to the resulting stream may cause the given onNext to be invoked more than once for an entry.

      Specified by:
      onNext in interface MessageStream<M extends Message>
      Parameters:
      onNext - The Consumer to invoke for each entry.
      Returns:
      A stream that will invoke the given onNext for each entry.

    • onComplete

      default MessageStream.Single<M> onComplete(Runnable completeHandler)
      Description copied from interface: MessageStream
      Returns a stream that invokes the given completeHandler when the stream completes normally. Throws an exception if this stream is unbounded.
      Specified by:
      onComplete in interface MessageStream<M extends Message>
      Parameters:
      completeHandler - The Runnable to invoke when the stream completes normally.
      Returns:
      A stream that invokes the completeHandler upon normal completion.

    • cast

      default <R extends Message> MessageStream.Single<R> cast()
      Description copied from interface: MessageStream
      Casts this stream to the given type. This method is provided to be more flexible with generics. It is the caller's responsibility to ensure the cast is valid. Failure to do so may result in ClassCastException when reading elements.
      Specified by:
      cast in interface MessageStream<M extends Message>
      Type Parameters:
      R - The type of Message to cast the MessageStream to.
      Returns:
      This instance, cast to the given Message of type T.

    • asCompletableFuture

      default CompletableFuture<@Nullable MessageStream.Entry<M>> asCompletableFuture()
      Returns a CompletableFuture that completes when this stream has been fully consumed, either normally or with an error.

      The future completes with the first MessageStream.Entry observed during stream consumption, or null if no entries were produced before completion.

      This method always drives full stream execution (via reduce), even though only the first encountered entry is retained. This is required to correctly support streams that may:

      • be composed via concatWith
      • perform side-effect-only processing via ignoreEntries()
      • defer emission until completion

      As a result, this operation is not a simple "fetch first element" operation, but a terminal stream execution that observes the first entry while ensuring complete stream traversal.

      Returns:
      A CompletableFuture completed with the first observed MessageStream.Entry, null if none were produced, or completed exceptionally if the stream fails.
      Throws:
      UnsupportedOperationException - if this stream is unbounded