Slack SDK for Java supports the Slack platform in a Java idiomatic way. The SDK written in Java so developers can use it in any JVM language including Kotlin, Groovy, and Scala.

Within the SDK, there are two different modules:

• Bolt for Java, which is a framework with a simple API that makes it easy to write modern Slack apps in Java.
• Slack API Client, for when you need a more customized approach to building a Slack app in Java.

If what you want to do is call Slack APIs in your existing services, we recommend using only the Slack API Client. If instead, you’re developing a new modern and interactive Slack app, we recommend Bolt for it. The framework enables developers to focus on the essential parts of their apps without being bothered by trifles.

Bolt for Java is a framework on the JVM that offers an abstraction layer to build Slack apps quickly using modern platform features. Refer to Getting Started with Bolt for detailed instructions.

package hello;

import com.slack.api.bolt.App;
import com.slack.api.bolt.jetty.SlackAppServer;

public class MyApp {
  public static void main(String[] args) throws Exception {
    // App expects env variables (SLACK_BOT_TOKEN, SLACK_SIGNING_SECRET)
    App app = new App();

    app.command("/hello", (req, ctx) -> {
      return ctx.ack(":wave: Hello!");
    });

    SlackAppServer server = new SlackAppServer(app);
    server.start(); // http://localhost:3000/slack/events
  }
}

For Socket Mode enabled apps, Getting Started with Bolt (Socket Mode) is available.

package hello;

import com.slack.api.bolt.App;
import com.slack.api.bolt.socket_mode.SocketModeApp;

public class MyApp {
  public static void main(String[] args) throws Exception {
    // App expects an env variable: SLACK_BOT_TOKEN
    App app = new App();

    app.command("/hello", (req, ctx) -> {
      return ctx.ack(":wave: Hello!");
    });

    // SocketModeApp expects an env variable: SLACK_APP_TOKEN
    new SocketModeApp(app).start();
  }
}

slack-api-client contains simple, easy-to-use, and flexibly configurable HTTP clients for making requests to Slack APIs. Refer to API Client Basics for details.

import com.slack.api.Slack;
import com.slack.api.methods.response.chat.ChatPostMessageResponse;

Slack slack = Slack.getInstance();
String token = System.getenv("SLACK_TOKEN");

ChatPostMessageResponse response = slack.methods(token).chatPostMessage(req -> req
  .channel("C1234567") // Channel ID
  .text(":wave: Hi from a bot written in Java!"));

The table below shows all the available modules in the Slack Java SDK. All of them have the same latest version as we release all at the same time, even in the case that some don't have any changes apart from updates on their dependency side.

All released versions are available on the Maven Central repositories. The latest version is:

The SDK supports OpenJDK 8 and higher LTS versions.

Users can expect every single patch release has been done after verifying functionality by running the basic CI builds with all LTS versions and all the unit tests have passed at least on the latest LTS version. We don't run comprehensive verifications with all OpenJDK distributions but it should be working with all of them.

If you get stuck, we’re here to help. The following are the best ways to get assistance working through your issue:

• Use our GitHub Issue Tracker for reporting bugs or requesting features
• Visit the Slack Developer Community for getting help using Slack SDK for Java or just generally bond with your fellow Slack developers.

The jSlack project has been transferred to @slackapi. The jSlack maintenance releases for security issues or major bugfixes will be continued at https://github.com/seratch/jslack-maintenance-releases .

We welcome contributions from everyone! Please check out our Contributor's Guide for how to contribute in a helpful and collaborative way.