I integrated Twitch4J into my Discord bot

Photo by Caspar Camille Rubin on Unsplash

In the past 12 hours I’ve managed to integrate my Twitch channel into a bot I wrote for my dev Discord server (you’re invited, by the way). Now, I’m able to have the bot send a message whenever my channel goes live. I’d gotten 98% of the way in writing the code that accomplished all of this, but I stopped working on it weeks ago to prioritize other work and it was broken at that point because I was missing a single line:

 this.twitchClient = twitchClient;

I had failed to instantiate the local variable from the constructor (shown in the TwitchServiceImplsnippet below), and so the app encountered a runtime error and wouldn’t start. Because the constructor exists in a class with the @Service annotation, Spring will infer arguments from the constructor and provide a @Bean for twitchClient. Because the provided twitchClient wasn’t assigned locally using this, the register() method ended up trying to use a null client.

    public TwitchServiceImpl(TwitchClient twitchClient) {
        this.twitchClient = twitchClient;
        register();
    }

The register() method uses the twitchClient to get the eventManager, which is how the bot is able to set listeners for ChannelGoLiveEvent and ChannelGoOfflineEvent for my channel at twitch.tv/michaellambgelo