Pusher Channels Java Client

There are two primary ways to handle events:

1. ChannelEventListener: Used during initial subscription. It handles both protocol-related events (like onSubscriptionSucceeded) and application data events via onEvent. You can specify which event names to listen for when passing this to subscribe.

2. SubscriptionEventListener: A simpler interface focused solely on application data events. You typically use this by calling channel.bind("event-name", listener) after a channel has been subscribed to.

To access the payload of an event, call event.getData().

// Using ChannelEventListener for both protocol and data events
Channel channel = pusher.subscribe("my-channel", new ChannelEventListener() {
    @Override
    public void onSubscriptionSucceeded(String channelName) {
        System.out.println("Subscribed!");
    }

    @Override
    public void onEvent(PusherEvent event) {
        // Called for incoming events named "foo", "bar" or "baz"
    }
}, "foo", "bar", "baz");

// Using SubscriptionEventListener via bind for specific application events
channel.bind("my-event", new SubscriptionEventListener() {
    @Override
    public void onEvent(PusherEvent event) {
        // Handle application event
        String data = event.getData();
    }
});

To be notified when a subscription succeeds, pass an implementation of ChannelEventListener to the subscribe method. To monitor the number of subscribers on a channel, bind to the pusher:subscription_count event using a SubscriptionEventListener.

// Listen for subscription success
Channel channel = pusher.subscribe("my-channel", new ChannelEventListener() {
    @Override
    public void onSubscriptionSucceeded(String channelName) {
        System.out.println("Subscribed to channel: " + channelName);
    }

    // Other ChannelEventListener methods
});

// Listen for subscription count events
channel.bind("pusher:subscription_count", new SubscriptionEventListener() {
    @Override
    public void onEvent(PusherEvent event) {
        System.out.println("Received event with data: " + event.toString());
        System.out.println("Subscription Count is: " + channel.getCount());
    }
});

You can trigger events directly from a client on private or presence channels once the subscription has been authorized and has succeeded.

Rules for Client Events: Events triggered by clients are called 'client events' and must follow these rules:

• Event names must have a client- prefix.
• They are subject to rate limits.
• You can only trigger an event after the subscription has successfully succeeded.

To ensure safety, always trigger client events within the onSubscriptionSucceeded callback of your channel listener.

PrivateChannel channel = pusher.subscribePrivate("private-channel",
    new PrivateChannelEventListener() {
        @Override
        public void onSubscriptionSucceeded(String channelName) {
            channel.trigger("client-myEvent", "{\"myName\":\"Bob\"}");
        }

        // Other PrivateChannelEventListener methods
    });

Presence channels are authorized private channels that expose information about currently subscribed users. Use subscribePresence and implement PresenceChannelEventListener to handle users joining (userSubscribed) or leaving (userUnsubscribed), as well as receiving the initial list of users (onUsersInformationReceived).

PresenceChannel channel = pusher.subscribePresence("presence-channel",
    new PresenceChannelEventListener() {
        @Override
        public void onUsersInformationReceived(String channelName, Set<User> users) {
            for (User user : users) {
                userSubscribed(channelName, user);
            }
        }

        @Override
        public void userSubscribed(String channelName, User user) {
            System.out.println(
                String.format("A new user joined channel [%s]: %s, %s",
                              channelName, user.getId(), user.getInfo())
            );

            if (user.equals(channel.getMe())) {
                System.out.println("me");
            }
        }

        @Override
        public void userUnsubscribed(String channelName, User user) {
            System.out.println(
                String.format("A user left channel [%s]: %s %s",
                              channelName, user.getId(), user.getInfo())
            );
        }

        // Other ChannelEventListener methods
    });