jSlack is a handy Java library which supports Incoming Webhook, Real Time Messaging API, and **all** API Methods
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README.md

jSlack

Maven Central Build Status

jSlack is a Java library to easily integrate your operations with Slack. The library currently supports the following APIs.

As per API Methods, this library supports all the APIs listed in github.com/slackapi/slack-api-specs as of May 2018.

Getting Started

Check the latest version on the Maven Central repository.

The following is an example using Maven. Of course, it's also possible to grab the library via Gradle, sbt and any other build tools.

<groupId>com.github.seratch</groupId>
<artifactId>jslack</artifactId>
<version>{latest version}</version>

See also: Getting started with groovysh

Examples

Incoming Webhook

Incoming Webhook is a simple way to post messages from external sources into Slack via ordinary HTTP requests.

https://api.slack.com/incoming-webhooks

jSlack naturally wraps its interface in Java. After lightly reading the official guide, you should be able to use it immediately.

import com.github.seratch.jslack.*;
import com.github.seratch.jslack.api.webhook.*;

// https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX
String url = System.getenv("SLACK_WEBHOOK_URL");

Payload payload = Payload.builder()
  .channel("#random")
  .username("jSlack Bot")
  .iconEmoji(":smile_cat:")
  .text("Hello World!")
  .build();

Slack slack = Slack.getInstance();
WebhookResponse response = slack.send(url, payload);
// response.code, response.message, response.body

Real Time Messaging API

Real Time Messaging API is a WebSocket-based API that allows you to receive events from Slack in real time and send messages as user.

https://api.slack.com/rtm

When you use this API through jSlack library, you need adding additional WebSocket libraries:

<dependency>
    <groupId>javax.websocket</groupId>
    <artifactId>javax.websocket-api</artifactId>
    <version>1.1</version>
</dependency>
<dependency>
    <groupId>org.glassfish.tyrus.bundles</groupId>
    <artifactId>tyrus-standalone-client</artifactId>
    <version>1.13</version>
</dependency>

The following example shows you a simple usage of RTM API.

import com.github.seratch.jslack.*;
import com.github.seratch.jslack.api.rtm.*;
import com.google.gson.*;

JsonParser jsonParser = new JsonParser();
String token = System.getenv("SLACK_BOT_API_TOKEN");

try (RTMClient rtm = new Slack().rtm(token)) {

  rtm.addMessageHandler((message) -> {
    JsonObject json = jsonParser.parse(message).getAsJsonObject();
    if (json.get("type") != null) {
      log.info("Handled type: {}", json.get("type").getAsString());
    }
  });

  RTMMessageHandler handler2 = (message) -> {
    log.info("Hello!");
  };

  rtm.addMessageHandler(handler2);

  // must connect within 30 seconds after issuing wss endpoint
  rtm.connect();

  rtm.removeMessageHandler(handler2);

} // #close method does #disconnect

The message, argument of messageHandler, is a string value in JSON format. You need to deserialize it with your favorite JSON library.

jSlack already depends on google-gson library. So you can use Gson as above example shows. If you prefer Jackson or other libraries, it's also possible.

API Methods

There are lots of APIs to integrate external sources into Slack. They follow HTTP RPC-style methods.

When the API call has been completed successfully, its response contains "ok": true and other specific fields.

{
    "ok": true
}

In some cases, it may contain warning field too.

{
    "ok": true,
    "warning": "something_problematic"
}

When the API call failed or had some warnings, its response contains "ok": false' and also have the error field which holds a string error code.

{
    "ok": false,
    "error": "something_bad"
}

jSlack simply wrap API interface. Find more examples in this library's test code.

import com.github.seratch.jslack.*;
import com.github.seratch.jslack.api.methods.request.channels.*;
import com.github.seratch.jslack.api.methods.response.channels.*;

Slack slack = Slack.getInstance();

String token = System.getenv("SLACK_BOT_TEST_API_TOKEN");
ChannelsCreateRequest channelCreation = ChannelsCreateRequest.builder().token(token).name(channelName).build();
ChannelsCreateResponse response = slack.methods().channelsCreate(channelCreation);

API Methods Examples

You can find more examples here: https://github.com/seratch/jslack/tree/master/src/test/java/com/github/seratch/jslack

Post a message to a channel
String token = "api-token";
Slack slack = Slack.getInstance();

// find all channels in the team
ChannelsListResponse channelsResponse = slack.methods().channelsList(
  ChannelsListRequest.builder().token(token).build());
assertThat(channelsResponse.isOk(), is(true));
// find #general
Channel general = channelsResponse.getChannels().stream()
        .filter(c -> c.getName().equals("general")).findFirst().get();

// https://slack.com/api/chat.postMessage
ChatPostMessageResponse postResponse = slack.methods().chatPostMessage(
  ChatPostMessageRequest.builder()
    .token(token)
    .channel(general.getId())
    .text("Hello World!")
    .build());
assertThat(postResponse.isOk(), is(true));

// timestamp of the posted message
String messageTimestamp = postResponse.getMessage().getTs();

Thread.sleep(1000L);

ChatDeleteResponse deleteResponse = slack.methods().chatDelete(
  ChatDeleteRequest.builder()
    .token(token)
    .channel(general.getId())
    .ts(messageTimestamp)
    .build());
assertThat(deleteResponse.isOk(), is(true));
Open a dialog modal
String token = "api-token";
    
// Required.  See https://api.slack.com/dialogs#implementation
String triggerId = "trigger-id";

Slack slack = Slack.getInstance();

DialogTextElement quanityTextElement = DialogTextElement.builder()
    .subtype(SubType.NUMBER)
    .label("Quantity")
    .name("quantity")
    .hint("The number you need")
    .maxLength(3)
    .minLength(1)
    .placeholder("Required quantity")
    .value("1")
    .build();

DialogSelectElement colourSelectElement = DialogSelectElement.builder()
    .name("colour")
    .label("Colour")
    .placeholder("Choose your preferred colour")
    .options(Arrays.asList(
        Option.builder().label("Red").value("#FF0000").build(),
        Option.builder().label("Green").value("#00FF00").build(),
        Option.builder().label("Blue").value("#0000FF").build(),
        Option.builder().label("Black").value("#000000").build(),
        Option.builder().label("White").value("#FFFFFF").build()
     ))
    .build();
    

Dialog dialog = Dialog.builder()
    .title("Request pens")
    .callbackId("pens-1122")
    .elements(Arrays.asList(quanityTextElement, colourSelectElement))
    .submitLabel("")
    .build();

DialogOpenResponse openDialogResponse = slack.methods().dialogOpen(
    DialogOpenRequest.builder()
    .token(token)
    .triggerId(triggerId)
    .dialog(dialog)
    .build());

(jSlack's Original) Shortcut APIs

Slack slack = Slack.getInstance();
ApiToken token = ApiToken.of(System.getenv("SLACK_OAUTH_ACCESS_TOKEN"));

Shortcut shortcut = slack.shortcut(token);

List<Message> messages = shortcut.findRecentMessagesByName(ChannelName.of("general"));
ReactionsAddResponse addReaction = shortcut.addReaction(messages.get(0), ReactionName.of("smile"));

ChatPostMessageResponse response = shortcut.post(ChannelName.of("general"), "hello, hello!");

Attachment attachment = Attachment.builder().text("text").footer("footer").build();
List<Attachment> attachments = Arrays.asList(attachment);
ChatPostMessageResponse response = shortcut.postAsBot(ChannelName.of("general"), "hello, hello!");

Preparations for running this library's unit tests.

Creating a Slack app

https://api.slack.com/apps

Setting up "OAuth & Permissions" for it

You need to select all permission scopes except for identity.*. After that, you also need to run "Reinstall App".

Setting up OAuth access tokens (both the normal one and the one as a bot)

Set the OAuth access tokens as env variables.

export SLACK_TEST_OAUTH_ACCESS_TOKEN=xoxp-*******************************************************
export SLACK_BOT_USER_TEST_OAUTH_ACCESS_TOKEN=xoxb-************************************

Creating at least one Slack user who has its email

Manually create a Slack user which has an email address for a unit test.

License

(The MIT License)

Copyright (c) Kazuhiro Sera