org.axonframework.messaging

Interface Message<T>

Type Parameters:

T - The type of payload contained in this Message

All Superinterfaces:

Serializable

All Known Subinterfaces:

CommandMessage<T>, CommandResultMessage<R>, DeadlineMessage<T>, DomainEventMessage<T>, EventMessage<T>, QueryMessage<T,R>, QueryResponseMessage<T>, ResultMessage<R>, SubscriptionQueryMessage<Q,I,U>, SubscriptionQueryUpdateMessage<U>, TrackedEventMessage<T>

All Known Implementing Classes:

AbstractMessage, GenericCommandMessage, GenericCommandResultMessage, GenericDeadlineMessage, GenericDomainEventMessage, GenericEventMessage, GenericMessage, GenericQueryMessage, GenericQueryResponseMessage, GenericResultMessage, GenericSubscriptionQueryMessage, GenericSubscriptionQueryUpdateMessage, GenericTrackedDomainEventMessage, GenericTrackedEventMessage, GrpcBackedCommandMessage, GrpcBackedQueryMessage, GrpcBackedResponseMessage, GrpcBackedSubscriptionQueryMessage, MessageDecorator, SerializedMessage

public interface Message<T>
extends Serializable

Representation of a Message, containing a Payload and MetaData. Typical examples of Messages are Commands and Events.

Instead of implementing Message directly, consider implementing {@code CommandMessage} or EventMessage instead.

Since:

2.0

Author:

Allard Buijze

See Also:

{@code CommandMessage}, EventMessage

Method Summary

Modifier and Type	Method and Description
Message<T>	andMetaData(Map<String,?> metaData) Returns a copy of this Message with it MetaData merged with the given metaData.
String	getIdentifier() Returns the identifier of this message.
MetaData	getMetaData() Returns the meta data for this event.
T	getPayload() Returns the payload of this Event.
Class<T>	getPayloadType() Returns the type of the payload.
default <R> SerializedObject<R>	serializeMetaData(Serializer serializer, Class<R> expectedRepresentation) Serialize the meta data of this message to the expectedRepresentation using given serializer.
default <R> SerializedObject<R>	serializePayload(Serializer serializer, Class<R> expectedRepresentation) Serialize the payload of this message to the expectedRepresentation using given serializer.
Message<T>	withMetaData(Map<String,?> metaData) Returns a copy of this Message with the given metaData.

Method Detail

getIdentifier

String getIdentifier()

Returns the identifier of this message. Two messages with the same identifiers should be interpreted as different representations of the same conceptual message. In such case, the meta-data may be different for both representations. The payload may be identical.

Returns:

the unique identifier of this message

getMetaData

MetaData getMetaData()

Returns the meta data for this event. This meta data is a collection of key-value pairs, where the key is a String, and the value is a serializable object.

Returns:

the meta data for this event

getPayload

T getPayload()

Returns the payload of this Event. The payload is the application-specific information.

Returns:

the payload of this Event

getPayloadType

Class<T> getPayloadType()

Returns the type of the payload.

Is semantically equal to getPayload().getClass(), but allows implementations to optimize by using lazy loading or deserialization.

Returns:

the type of payload.

withMetaData

Message<T> withMetaData(Map<String,?> metaData)

Returns a copy of this Message with the given metaData. The payload remains unchanged.

While the implementation returned may be different than the implementation of this, implementations must take special care in returning the same type of Message (e.g. EventMessage, DomainEventMessage) to prevent errors further downstream.

Parameters:

metaData - The new MetaData for the Message

Returns:

a copy of this message with the given MetaData

andMetaData

Message<T> andMetaData(Map<String,?> metaData)

Returns a copy of this Message with it MetaData merged with the given metaData. The payload remains unchanged.

Parameters:

metaData - The MetaData to merge with

Returns:

a copy of this message with the given MetaData

serializePayload

default <R> SerializedObject<R> serializePayload(Serializer serializer,
                                                 Class<R> expectedRepresentation)

Serialize the payload of this message to the expectedRepresentation using given serializer. This method should return the same SerializedObject instance when invoked multiple times using the same serializer.

Type Parameters:

R - The type of the serialized data

Parameters:

serializer - The serializer to serialize payload with

expectedRepresentation - The type of data to serialize to

Returns:

a SerializedObject containing the serialized representation of the message's payload

serializeMetaData

default <R> SerializedObject<R> serializeMetaData(Serializer serializer,
                                                  Class<R> expectedRepresentation)

Serialize the meta data of this message to the expectedRepresentation using given serializer. This method should return the same SerializedObject instance when invoked multiple times using the same serializer.

Type Parameters:

R - The type of the serialized data

Parameters:

serializer - The serializer to serialize meta data with

expectedRepresentation - The type of data to serialize to

Returns:

a SerializedObject containing the serialized representation of the message's meta data