```
public abstract class ChannelBase
extends EventEmitter<ChannelEvent, ChannelStateListener>
                    
```
Enables messages to be published and subscribed to. Also enables historic messages to be retrieved and provides access to the Presence object of a channel.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`public interface`	`ChannelBase.MessageListener`	An interface whereby a client maybe notified of message on a channel.

Field Summary

Fields
Modifier and Type	Field	Description
`public final String`	`name`
`public final Presence`	`presence`
`public ChannelState`	`state`
`public ErrorInfo`	`reason`
`public ChannelProperties`	`properties`
`public final RealtimeAnnotations`	`annotations`
`ChannelOptions`	`options`
`private Map<String, String>`	`params`

Method Summary

Modifier and Type	Method	Description
`void`	`setState(ChannelState newState, ErrorInfo reason)`
`ChannelOptions`	`getOptions()`
`void`	`setOptions(ChannelOptions options)`	Sets the ChannelOptions for the channel.
`Map<String, String>`	`getParams()`
`RealtimeObjects`	`getObjects()`
`void`	`attach()`	Attach to this channel ensuring the channel is created in the Ably system and all messages publishedon the channel are received by any channel listeners registered using subscribe.
`void`	`attach(CompletionListener listener)`	Attach to this channel ensuring the channel is created in the Ably system and all messages publishedon the channel are received by any channel listeners registered using subscribe.
`void`	`detach()`	Detach from this channel.
`void`	`markAsReleased()`	Mark channel as released that means we can't perform any operation on this channel anymore
`void`	`detach(CompletionListener listener)`	Detach from this channel.
`void`	`sync()`
`void`	`setConnected()`
`void`	`setConnectionFailed(ErrorInfo reason)`	If the connection state enters the FAILED state, then an ATTACHINGor ATTACHED channel state will transition to FAILED and set theChannel#errorReason
`void`	`setConnectionClosed(ErrorInfo reason)`	(RTL3b) If the connection state enters the CLOSED state, then anATTACHING or ATTACHED channel state will transition to DETACHED.
`synchronized void`	`setSuspended(ErrorInfo reason, boolean notifyStateChange)`	(RTL3c) If the connection state enters the SUSPENDED state, then anATTACHING or ATTACHED channel state will transition to SUSPENDED.(RTN15c3) The client library should initiate an attach for channelsthat are in the SUSPENDED state.
`synchronized void`	`setReinitialized()`	Internal(RTN11d) Resets channels back to initialized and clears error reason
`synchronized void`	`unsubscribe()`	Deregisters all listeners to messages on this channel.This removes all earlier subscriptions.
`synchronized void`	`subscribe(ChannelBase.MessageListener listener)`	Registers a listener for messages on this channel.The caller supplies a listener function, which is called each time one or more messages arrives on the channel.
`synchronized void`	`unsubscribe(ChannelBase.MessageListener listener)`	Deregisters the given listener (for any/all event names).This removes an earlier subscription.
`synchronized void`	`subscribe(String name, ChannelBase.MessageListener listener)`	Registers a listener for messages with a given event name on this channel.The caller supplies a listener function, which is called each time one or more matching messages arrives on the channel.
`synchronized void`	`unsubscribe(String name, ChannelBase.MessageListener listener)`	Deregisters the given listener for the specified event name.
`synchronized void`	`subscribe(Array<String> names, ChannelBase.MessageListener listener)`	Registers a listener for messages on this channel for multiple event name values.The caller supplies a listener function, which is called each time one or more matching messages arrives on the channel.
`synchronized void`	`unsubscribe(Array<String> names, ChannelBase.MessageListener listener)`	Deregisters the given listener from all event names in the array.
`void`	`publish(String name, Object data)`	Publishes a single message to the channel with the given event name and payload.
`void`	`publish(Message message)`	Publishes a message to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
`void`	`publish(Array<Message> messages)`	Publishes an array of messages to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
`void`	`publish(String name, Object data, CompletionListener listener)`	Publishes a single message to the channel with the given event name and payload.
`void`	`publish(String name, Object data, Callback<PublishResult> callback)`	Publishes a single message to the channel with the given event name and payload.
`void`	`publish(Message message, CompletionListener listener)`	Publishes a message to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
`void`	`publish(Message message, Callback<PublishResult> callback)`	Publishes a message to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
`synchronized void`	`publish(Array<Message> messages, CompletionListener listener)`	Publishes an array of messages to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
`synchronized void`	`publish(Array<Message> messages, Callback<PublishResult> listener)`
`Message`	`getMessage(String serial)`	Retrieves the latest version of a specific message by its serial identifier.
`void`	`getMessageAsync(String serial, Callback<Message> callback)`	Asynchronously retrieves the latest version of a specific message by its serial identifier.
`void`	`updateMessage(Message message)`	Asynchronously updates an existing message.
`void`	`updateMessage(Message message, MessageOperation operation)`	Asynchronously updates an existing message.
`void`	`updateMessage(Message message, MessageOperation operation, Callback<UpdateDeleteResult> listener)`	Asynchronously updates an existing message.
`void`	`updateMessage(Message message, Callback<UpdateDeleteResult> listener)`	Asynchronously updates an existing message.
`void`	`deleteMessage(Message message)`	Asynchronously marks a message as deleted.
`void`	`deleteMessage(Message message, MessageOperation operation)`	Asynchronously marks a message as deleted.
`void`	`deleteMessage(Message message, MessageOperation operation, Callback<UpdateDeleteResult> listener)`	Asynchronously marks a message as deleted.
`void`	`deleteMessage(Message message, Callback<UpdateDeleteResult> callback)`	Asynchronously marks a message as deleted.
`void`	`appendMessage(Message message)`	Asynchronously appends message text to the end of the message data.
`void`	`appendMessage(Message message, MessageOperation operation)`	Asynchronously appends message text to the end of the message.
`void`	`appendMessage(Message message, MessageOperation operation, Callback<UpdateDeleteResult> listener)`	Asynchronously appends message text to the end of the message.
`void`	`appendMessage(Message message, Callback<UpdateDeleteResult> callback)`	Asynchronously appends message text to the end of the message.
`PaginatedResult<Message>`	`getMessageVersions(String serial, Array<Param> params)`	Retrieves all historical versions of a specific message.
`void`	`getMessageVersionsAsync(String serial, Array<Param> params, Callback<AsyncPaginatedResult<Message>> callback)`	Asynchronously retrieves all historical versions of a specific message.
`PaginatedResult<Message>`	`history(Array<Param> params)`	Retrieves a PaginatedResult object, containing an array of historical Message objects for the channel.If the channel is configured to persist messages, then messages can be retrieved from history for up to 72 hours in the past.If not, messages can only be retrieved from history for up to two minutes in the past.
`void`	`historyAsync(Array<Param> params, Callback<AsyncPaginatedResult<Message>> callback)`	Asynchronously retrieves a PaginatedResult object, containing an array of historical Message objects for the channel.If the channel is configured to persist messages, then messages can be retrieved from history for up to 72 hours in the past.If not, messages can only be retrieved from history for up to two minutes in the past.
`void`	`emit(ChannelState state, ChannelStateListener.ChannelStateChange channelStateChange)`
`void`	`on(ChannelState state, ChannelStateListener listener)`
`void`	`once(ChannelState state, ChannelStateListener listener)`
`void`	`sendProtocolMessage(ProtocolMessage protocolMessage, CompletionListener listener)`	(Internal) Sends a protocol message and provides a callback for completion.

Methods inherited from class io.ably.lib.util.EventEmitter
emit, off, off, off, on, on, once, once
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - setState
```
 void setState(ChannelState newState, ErrorInfo reason)
```
  - getOptions
```
 ChannelOptions getOptions()
```
  - setOptions
```
 void setOptions(ChannelOptions options)
```
    Sets the ChannelOptions for the channel.
    Spec: RTL16
    
    Parameters:
    
    options - A ChannelOptions object.
  - getParams
```
 Map<String, String> getParams()
```
  - getObjects
```
 RealtimeObjects getObjects()
```
  - attach
```
 void attach()
```
    Attach to this channel ensuring the channel is created in the Ably system and all messages publishedon the channel are received by any channel listeners registered using subscribe.Any resulting channel state change will be emitted to any listeners registered using the on or once methods.As a convenience, attach() is called implicitly if subscribe for the channel is called,or enter or subscribe are called on the Presence object for this channel.
    Spec: RTL4d
  - attach
```
 void attach(CompletionListener listener)
```
    Attach to this channel ensuring the channel is created in the Ably system and all messages publishedon the channel are received by any channel listeners registered using subscribe.Any resulting channel state change will be emitted to any listeners registered using the on or once methods.As a convenience, attach() is called implicitly if subscribe for the channel is called,or enter or subscribe are called on the Presence object for this channel.
    Spec: RTL4d
    
    Parameters:
    
    listener - A callback may optionally be passed in to this call to be notified of success or failure of the operation.
  - detach
```
 void detach()
```
    Detach from this channel.Any resulting channel state change is emitted to any listeners registered using the on or once methods.Once all clients globally have detached from the channel, the channel will be released in the Ably service within two minutes.
    Spec: RTL5e
  - markAsReleased
```
 void markAsReleased()
```
    Mark channel as released that means we can't perform any operation on this channel anymore
  - detach
```
 void detach(CompletionListener listener)
```
    Detach from this channel.Any resulting channel state change is emitted to any listeners registered using the on or once methods.Once all clients globally have detached from the channel, the channel will be released in the Ably service within two minutes.
    Spec: RTL5e
    
    Parameters:
    
    listener - A callback may optionally be passed in to this call to be notified of success or failure of the operation.
  - sync
```
@Deprecated() void sync()
```
  - setConnected
```
 void setConnected()
```
  - setConnectionFailed
```
 void setConnectionFailed(ErrorInfo reason)
```
    If the connection state enters the FAILED state, then an ATTACHINGor ATTACHED channel state will transition to FAILED and set theChannel#errorReason
  - setConnectionClosed
```
 void setConnectionClosed(ErrorInfo reason)
```
    (RTL3b) If the connection state enters the CLOSED state, then anATTACHING or ATTACHED channel state will transition to DETACHED.
  - setSuspended
```
 synchronized void setSuspended(ErrorInfo reason, boolean notifyStateChange)
```
    (RTL3c) If the connection state enters the SUSPENDED state, then anATTACHING or ATTACHED channel state will transition to SUSPENDED.(RTN15c3) The client library should initiate an attach for channelsthat are in the SUSPENDED state. For all channels in the ATTACHINGor ATTACHED state, the client library should fail any previously queuedmessages for that channel and initiate a new attach.This also gets called when a connection enters CONNECTED but with anon-fatal error for a failed reconnect (RTN16e).
  - setReinitialized
```
 synchronized void setReinitialized()
```
    Internal
    (RTN11d) Resets channels back to initialized and clears error reason
  - unsubscribe
```
 synchronized void unsubscribe()
```
    Deregisters all listeners to messages on this channel.This removes all earlier subscriptions.
    Spec: RTL8a, RTE5
  - subscribe
```
 synchronized void subscribe(ChannelBase.MessageListener listener)
```
    Registers a listener for messages on this channel.The caller supplies a listener function, which is called each time one or more messages arrives on the channel.
    Spec: RTL7a
    
    Parameters:
    
    listener - A listener may optionally be passed in to this call to be notified of success or failureof the channel attach operation.
  - unsubscribe
```
 synchronized void unsubscribe(ChannelBase.MessageListener listener)
```
    Deregisters the given listener (for any/all event names).This removes an earlier subscription.
    Spec: RTL8a
    
    Parameters:
    
    listener - An event listener function.
  - subscribe
```
 synchronized void subscribe(String name, ChannelBase.MessageListener listener)
```
    Registers a listener for messages with a given event name on this channel.The caller supplies a listener function, which is called each time one or more matching messages arrives on the channel.
    Spec: RTL7b
    
    Parameters:
    
    name - The event name.
    
    listener - A listener may optionally be passed in to this call to be notified of success or failureof the channel attach operation.
  - unsubscribe
```
 synchronized void unsubscribe(String name, ChannelBase.MessageListener listener)
```
    Deregisters the given listener for the specified event name.This removes an earlier event-specific subscription
    Spec: RTL8a
    
    Parameters:
    
    name - The event name.
    
    listener - An event listener function.
  - subscribe
```
 synchronized void subscribe(Array<String> names, ChannelBase.MessageListener listener)
```
    Registers a listener for messages on this channel for multiple event name values.The caller supplies a listener function, which is called each time one or more matching messages arrives on the channel.
    Spec: RTL7a
    
    Parameters:
    
    names - An array of event names.
    
    listener - A listener may optionally be passed in to this call to be notified of success or failureof the channel attach operation.
  - unsubscribe
```
 synchronized void unsubscribe(Array<String> names, ChannelBase.MessageListener listener)
```
    Deregisters the given listener from all event names in the array.
    Spec: RTL8a
    
    Parameters:
    
    names - An array of event names.
    
    listener - An event listener function.
  - publish
```
@NonBlocking() void publish(String name, Object data)
```
    Publishes a single message to the channel with the given event name and payload.When publish is called with this client library, it won't attempt to implicitly attach to the channel,so long as transient publishing is available in the library.Otherwise, the client will implicitly attach.
    Spec: RTL6i
    
    Parameters:
    
    name - the event name
    
    data - the message payload
  - publish
```
@NonBlocking() void publish(Message message)
```
    Publishes a message to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
    Spec: RTL6i
    
    Parameters:
    
    message - A Message object.
  - publish
```
@NonBlocking() void publish(Array<Message> messages)
```
    Publishes an array of messages to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
    Spec: RTL6i
    
    Parameters:
    
    messages - An array of Message objects.
  - publish
```
@Deprecated()@NonBlocking() void publish(String name, Object data, CompletionListener listener)
```
    Publishes a single message to the channel with the given event name and payload.When publish is called with this client library, it won't attempt to implicitly attach to the channel,so long as transient publishing is available in the library.Otherwise, the client will implicitly attach.
    Spec: RTL6i
    
    Parameters:
    
    name - the event name
    
    data - the message payload
    
    listener - A listener may optionally be passed in to this call to be notified of success or failure of the operation.
  - publish
```
@NonBlocking() void publish(String name, Object data, Callback<PublishResult> callback)
```
    Publishes a single message to the channel with the given event name and payload.When publish is called with this client library, it won't attempt to implicitly attach to the channel,so long as transient publishing is available in the library.Otherwise, the client will implicitly attach.
    Spec: RTL6i
    
    Parameters:
    
    name - the event name
    
    data - the message payload
    
    callback - A callback may optionally be passed in to this call to be notified of success or failure of the operation,receiving a PublishResult with message serial(s) on success.
  - publish
```
@Deprecated()@NonBlocking() void publish(Message message, CompletionListener listener)
```
    Publishes a message to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
    Spec: RTL6i
    
    Parameters:
    
    message - A Message object.
    
    listener - A listener may optionally be passed in to this call to be notified of success or failure of the operation.
  - publish
```
@NonBlocking() void publish(Message message, Callback<PublishResult> callback)
```
    Publishes a message to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
    Spec: RTL6i
    
    Parameters:
    
    message - A Message object.
    
    callback - A callback may optionally be passed in to this call to be notified of success or failure of the operation,receiving a PublishResult with message serial(s) on success.
  - publish
```
@Deprecated()@NonBlocking() synchronized void publish(Array<Message> messages, CompletionListener listener)
```
    Publishes an array of messages to the channel.When publish is called with this client library, it won't attempt to implicitly attach to the channel.
    Spec: RTL6i
    
    Parameters:
    
    messages - An array of Message objects.
    
    listener - A listener may optionally be passed in to this call to be notified of success or failure of the operation.
  - publish
```
@NonBlocking() synchronized void publish(Array<Message> messages, Callback<PublishResult> listener)
```
  - getMessage
```
@Blocking() Message getMessage(String serial)
```
    Retrieves the latest version of a specific message by its serial identifier.
    This method allows you to fetch the current state of a message, including any updatesor deletions that have been applied since its creation.
    
    Parameters:
    
    serial - The unique serial identifier of the message to retrieve.
  - getMessageAsync
```
@NonBlocking() void getMessageAsync(String serial, Callback<Message> callback)
```
    Asynchronously retrieves the latest version of a specific message by its serial identifier.
    
    Parameters:
    
    serial - The unique serial identifier of the message to retrieve.
    
    callback - A callback to handle the result asynchronously.
  - updateMessage
```
@NonBlocking() void updateMessage(Message message)
```
    Asynchronously updates an existing message.
    
    Parameters:
    
    message - A Message object containing the fields to update and the serial identifier.
  - updateMessage
```
@NonBlocking() void updateMessage(Message message, MessageOperation operation)
```
    Asynchronously updates an existing message.
    
    Parameters:
    
    message - A Message object containing the fields to update and the serial identifier.
    
    operation - operation metadata such as clientId, description, or metadata in the version fieldThis callback is invoked on a background thread.
  - updateMessage
```
@NonBlocking() void updateMessage(Message message, MessageOperation operation, Callback<UpdateDeleteResult> listener)
```
    Asynchronously updates an existing message.
    
    Parameters:
    
    message - A Message object containing the fields to update and the serial identifier.
    
    operation - operation metadata such as clientId, description, or metadata in the version field
    
    listener - A callback to be notified of the outcome of this operation.
  - updateMessage
```
@NonBlocking() void updateMessage(Message message, Callback<UpdateDeleteResult> listener)
```
    Asynchronously updates an existing message.
    
    Parameters:
    
    message - A Message object containing the fields to update and the serial identifier.
    
    listener - A callback to be notified of the outcome of this operation.
  - deleteMessage
```
@NonBlocking() void deleteMessage(Message message)
```
    Asynchronously marks a message as deleted.
    
    Parameters:
    
    message - A Message object containing the serial identifier and operation metadata.
  - deleteMessage
```
@NonBlocking() void deleteMessage(Message message, MessageOperation operation)
```
    Asynchronously marks a message as deleted.
    
    Parameters:
    
    message - A Message object containing the serial identifier and operation metadata.
    
    operation - operation metadata such as clientId, description, or metadata in the version fieldThis callback is invoked on a background thread.
  - deleteMessage
```
@NonBlocking() void deleteMessage(Message message, MessageOperation operation, Callback<UpdateDeleteResult> listener)
```
    Asynchronously marks a message as deleted.
    
    Parameters:
    
    message - A Message object containing the serial identifier and operation metadata.
    
    operation - operation metadata such as clientId, description, or metadata in the version field
    
    listener - A callback to be notified of the outcome of this operation.
  - deleteMessage
```
@NonBlocking() void deleteMessage(Message message, Callback<UpdateDeleteResult> callback)
```
    Asynchronously marks a message as deleted.
    
    Parameters:
    
    message - A Message object containing the serial identifier and operation metadata.
    
    callback - A callback to be notified of the outcome of this operation.
  - appendMessage
```
@NonBlocking() void appendMessage(Message message)
```
    Asynchronously appends message text to the end of the message data.
    
    Parameters:
    
    message - A Message object containing the serial identifier and data to append.
  - appendMessage
```
@NonBlocking() void appendMessage(Message message, MessageOperation operation)
```
    Asynchronously appends message text to the end of the message.
    
    Parameters:
    
    message - A Message object containing the serial identifier and data to append.
    
    operation - operation details such as clientId, description, or metadataThis callback is invoked on a background thread.
  - appendMessage
```
@NonBlocking() void appendMessage(Message message, MessageOperation operation, Callback<UpdateDeleteResult> listener)
```
    Asynchronously appends message text to the end of the message.
    
    Parameters:
    
    message - A Message object containing the serial identifier and data to append.
    
    operation - operation details such as clientId, description, or metadata
    
    listener - A callback to be notified of the outcome of this operation.
  - appendMessage
```
@NonBlocking() void appendMessage(Message message, Callback<UpdateDeleteResult> callback)
```
    Asynchronously appends message text to the end of the message.
    
    Parameters:
    
    message - A Message object containing the serial identifier and data to append.
    
    callback - A callback to be notified of the outcome of this operation.
  - getMessageVersions
```
@Blocking() PaginatedResult<Message> getMessageVersions(String serial, Array<Param> params)
```
    Retrieves all historical versions of a specific message.
    This method returns a paginated result containing all versions of the message,ordered chronologically. Each version includes metadata about when and by whomthe message was modified.
    
    Parameters:
    
    serial - The unique serial identifier of the message.
    
    params - Query parameters for filtering or pagination (e.g., limit, start, end).
  - getMessageVersionsAsync
```
@NonBlocking() void getMessageVersionsAsync(String serial, Array<Param> params, Callback<AsyncPaginatedResult<Message>> callback)
```
    Asynchronously retrieves all historical versions of a specific message.
    
    Parameters:
    
    serial - The unique serial identifier of the message.
    
    params - Query parameters for filtering or pagination.
    
    callback - A callback to handle the result asynchronously.
  - history
```
 PaginatedResult<Message> history(Array<Param> params)
```
    Retrieves a PaginatedResult object, containing an array of historical Message objects for the channel.If the channel is configured to persist messages, then messages can be retrieved from history for up to 72 hours in the past.If not, messages can only be retrieved from history for up to two minutes in the past.
    Spec: RSL2a
    
    Parameters:
    
    params - the request params:start (RTL10a) - The time from which messages are retrieved, specified as milliseconds since the Unix epoch.
  - historyAsync
```
 void historyAsync(Array<Param> params, Callback<AsyncPaginatedResult<Message>> callback)
```
    Asynchronously retrieves a PaginatedResult object, containing an array of historical Message objects for the channel.If the channel is configured to persist messages, then messages can be retrieved from history for up to 72 hours in the past.If not, messages can only be retrieved from history for up to two minutes in the past.
    Spec: RSL2a
    
    Parameters:
    
    params - the request params:start (RTL10a) - The time from which messages are retrieved, specified as milliseconds since the Unix epoch.
    
    callback - Callback with AsyncPaginatedResult object containing an array of Message objects.
  - emit
```
 void emit(ChannelState state, ChannelStateListener.ChannelStateChange channelStateChange)
```
  - on
```
 void on(ChannelState state, ChannelStateListener listener)
```
  - once
```
 void once(ChannelState state, ChannelStateListener listener)
```
  - sendProtocolMessage
```
 void sendProtocolMessage(ProtocolMessage protocolMessage, CompletionListener listener)
```
    (Internal) Sends a protocol message and provides a callback for completion.
    
    Parameters:
    
    protocolMessage - the protocol message to be sent
    
    listener - the listener to be notified upon completion of the message delivery

Class ChannelBase

Nested Class Summary

Field Summary

Method Summary

Methods inherited from class io.ably.lib.util.EventEmitter

Methods inherited from class java.lang.Object

Method Detail

setState

getOptions

setOptions

getParams

getObjects

attach

attach

detach

markAsReleased

detach

sync

setConnected

setConnectionFailed

setConnectionClosed

setSuspended

setReinitialized

unsubscribe

subscribe

unsubscribe

subscribe

unsubscribe

subscribe

unsubscribe

publish

publish

publish

publish

publish

publish

publish

publish

publish

getMessage

getMessageAsync

updateMessage

updateMessage

updateMessage

updateMessage

deleteMessage

deleteMessage

deleteMessage

deleteMessage

appendMessage

appendMessage

appendMessage

appendMessage

getMessageVersions

getMessageVersionsAsync

history

historyAsync

emit

on

once

sendProtocolMessage