Message overview

The Nexconn SDK defines the Message class for transmitting and managing messages.

Message model

The Message class encapsulates the following key data:

• Transmission properties: Sender ID, receiver ID, channel type, and other routing information.
• Message content: The actual payload of a message, represented by a subclass of MessageContent (for standard messages) or MediaMessageContent (for media messages). For example, TextMessage is a standard message content type, while ImageMessage is a media message content type. The content type determines which send method to use.

tip

In this documentation, "message" (e.g., text message, voice message) sometimes refers to the specific content class that extends MessageContent or MediaMessageContent.

The following table describes the key properties of the Message class. For a complete list, see the API reference.

Property	Type	Description
messageType	String	The identifier for the message type. See Message type overview.
content	MessageContent?	The actual message payload. Must be a subclass of MessageContent or MediaMessageContent. The Chat SDK provides built-in message types with cross-platform consistent structures (see Message type overview), such as text, voice, image, and GIF. You can also create custom message types.
channelIdentifier	ChannelIdentifier	Channel identifier containing channel type and channel ID. Use channelIdentifier.channelType and channelIdentifier.channelId to access them. See Channel overview.
senderUserId	String?	The user ID of the message sender.
clientId	Int	The local message ID, a unique auto-increment index in local storage.
messageId	String?	The server-assigned globally unique message ID. Only set for successfully sent messages.
direction	MessageDirection	The message direction enum: SEND or RECEIVE.
sentTime	Long	The server timestamp (in milliseconds, UNIX epoch) when the message arrived at the server.
sentStatus	SentStatus	The send status: NONE, SENDING, SENT, FAILED, CANCELED, RECEIVED, READ, or DESTROYED.
receivedStatusInfo	MessageReceivedStatusInfo	The received message status info, including isRead, isDownloaded, isListened, isRetrieved, and isMultipleReceive. See Message received status.
metadata	Map<String, String>?	The message metadata in key-value format. Supports remote sync. See Message metadata.
needReceipt	Boolean	Whether a read receipt is required. See Read receipt.
sentReceipt	Boolean	Whether a read receipt has been sent. See Read receipt.
modifyInfo	MessageModifyInfo?	Message modification info. See Update messages.
isCounted	Boolean	Whether this message is counted for unread count.
isPersisted	Boolean	Whether this message is persisted in local storage.

MessageContent

The Message class contains a content property representing the actual message payload. Message content types must extend one of these base classes:

• MessageContent — The base class for standard message content. For example, the built-in TextMessage extends MessageContent.
• MediaMessageContent — The base class for media message content. It extends MessageContent and adds media file handling logic. For example, the built-in ImageMessage extends MediaMessageContent. When sending or receiving media messages, the SDK automatically handles file upload and download.

The Chat SDK provides built-in, cross-platform consistent message content types (see Message type overview), including text, voice, image, and GIF. To create custom messages, extend MessageContent or MediaMessageContent.

Message storage policy

The client SDK and server use the MessageTag annotation to identify a message's type, storage policy, and whether it counts toward the unread count. MessageTag is a Java annotation applied to message content classes. Every class that extends MessageContent or MediaMessageContent must have a MessageTag annotation.

For built-in message types, the MessageTag is automatically applied. No extra configuration is needed.

To create custom message types, learn how to set up message annotations correctly:

• Custom message types