General API¶

A Backendless application can publish messages to Backendless for subsequent distribution to subscribers. A message must be published to a channel. Backendless supports unlimited number of channels per application. Channels can be used as a filtering mechanism - subscribers see the messages published only to the channel they subscribe to.

There is only one API for all types of message publishing. It supports the following scenarios:

Basic message publish
Publishing with headers - can be used for conditional delivery
Delayed publishing
Repeated publishing

API Specification¶

Blocking Methods¶

Publishes a message to the default channel.

public MessageStatus Backendless.Messaging.publish( Object message ) 
                                                    throws BackendlessException

Same as above, but publishes to the specified channel.

public MessageStatus Backendless.Messaging.publish( String channelName, 
                                                    Object message ) 
                                                    throws BackendlessException

Publishes a message to the default channel. May have headers and/or subtopic defined in the publishOptions argument.

public MessageStatus Backendless.Messaging.publish( Object message, 
                                                    PublishOptions publishOptions ) 
                                                    throws BackendlessException

Same as above, but publishes to the specified channel.

public MessageStatus Backendless.Messaging.publish( String channelName, 
                                                    Object message, 
                                                    PublishOptions publishOptions ) 
                                                    throws BackendlessException

Publishes a message to the default channel. May have headers and/or subtopic defined in the publishOptions argument. The deliveryOptions argument can be used to:

Publish the message at a later time (delayed publishing).
Specify that the message should be republished multiple times (repeated publishing).

public MessageStatus Backendless.Messaging.publish( Object message, 
                                                    PublishOptions publishOptions, 
                                                    DeliveryOptions deliveryOptions )
                                                    throws BackendlessException

Same as above, but publishes to the specified channel.

public MessageStatus Backendless.Messaging.publish( String channelName, 
                                                    Object message, 
                                                    PublishOptions publishOptions, 
                                                    DeliveryOptions deliveryOptions ) 
                                                    throws BackendlessException

Non-blocking Methods¶

The same set of methods is available for the non-blocking invocation. The difference in the method signatures is the AsyncCallback<MessageStatus> argument:

// Publishes a message to the default channel:
public void Backendless.Messaging.publish( Object message, 
                                           AsyncCallback<MessageStatus> responder )

// Same as above, but publishes to the specified channel:
public void Backendless.Messaging.publish( String channelName, 
                                           Object message, 
                                           AsyncCallback<MessageStatus> responder )

// Publishes a message to the default channel. 
// May have headers and/or subtopic defined in the publishOptions argument.
public void Backendless.Messaging.publish( Object message, 
                                           PublishOptions publishOptions, 
                                           AsyncCallback<MessageStatus> responder )

// Same as above, but publishes to the specified channel:
public void Backendless.Messaging.publish( String channelName, 
                                           Object message, 
                                           PublishOptions publishOptions, 
                                           AsyncCallback<MessageStatus> responder )

// Publishes a message to the default channel. 
// May have headers and/or subtopic defined in the publishOptions argument. 
// The deliveryOptions argument can be used to:
//    1. Publish the message at a later time (delayed publishing)
//    2. Specify that the message should be republished multiple times (repeated publishing):
public void Backendless.Messaging.publish( Object message, 
                                           PublishOptions publishOptions, 
                                           DeliveryOptions deliveryOptions, 
                                           AsyncCallback<MessageStatus> responder )

// Same as above, but publishes to the specified channel:
public void Backendless.Messaging.publish( String channelName, 
                                           Object message, 
                                           PublishOptions publishOptions, 
                                           DeliveryOptions deliveryOptions, 
                                           AsyncCallback<MessageStatus> responder )

where:

Argument	Description
`channelName`	name of the channel to publish the message to. If the channel does not exist, Backendless automatically creates it.
`message`	object to publish. The object can be of any data type - a primitive value, `String`, `Date`, a user-defined complex type, a collection or an array of these types.
`publishOptions`	an instance of `PublishOptions`. When provided may contain publisher ID (an arbitrary, application-specific string value identifying the publisher), subtopic value and/or a collection of headers. See the Publish with Headers section for examples.
`deliveryOptions`	an instance of `DeliveryOptions`. When provided may specify options for message delivery such as: deliver as a push notification, delayed delivery or repeated delivery. See the Delayed Publish and Repeated Publish sections for examples.

Return value¶

Argument	Description
`MessageStatus`	an object which contains ID of the published message. Use the `getMessageId()` method to get the ID assigned to the message by the backend (the ID is needed to check the message publishing status or cancel the message).

Errors¶

The following errors may occur during the message publishing API call. See the Error Handling section for details on how to retrieve the error code when the server returns an error:

Error Code	Description
5003	Invalid `repeatExpiresAt` date in delivery options.
5007	User does not have the permission to publish messages
5030	Invalid `publishAt` date in the delivery options.