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RoboSlack is a Java 8 API which handles all aspects of authenticating and sending messages to Slack as an incoming webhook service. RoboSlack features a fully-articulated Java API that allows consumers to easily create rich Slack messages with features including:

  1. Text with Slack Markdown features (bold, italic, lists, quotes, emojis, Slack dates)
  2. Links
  3. Attachments
  4. Pictures, Icons, Thumbnails
  5. Titles, authors, footers
  6. Notifications, including: !channel, !here, @users, #channel

It also handles Slack authentication tokens and can perform synchronous message posting requests with basic error handling.

At this time, RoboSlack does not support core Slack API features like buttons and other interactive items within Slack messages.

Core libraries:

  • roboslack-webhook: Implementation of the Incoming Webhooks functionality via the SlackWebHookService

Auxiliary libraries:

  • roboslack-api: Data structures for creating and sending messages
  • roboslack-webhook-api: Data structures and service interfaces for using Incoming Webhooks


Artifacts are published to Bintray, the following is an example gradle dependency configuration:

repositories {
    maven { url  "" }

dependencies {
    compile "com.palantir.roboslack:roboslack-webhook:${version}"


Provides a mechanism to send messages through the use of a WebHookToken.

Setting up a WebHookToken

  1. As an administrator for your Slack team, visit the Incoming Webhook application page
  2. Select the Post to Channel channel that you wish to use
    1. NOTE that RoboSlack will allow you to post to any channel, but the Post to Channel option will be the default channel the web hook client (ie. RoboSlack) posts to if no channel is specified
  3. Click Add Incoming WebHooks integration
  4. Copy the Webhook URL into a safe place

Using a WebHookToken

The Incoming Webhook URL should look something like the following:

// (where each `?` represents one alphanumeric character)

The WebHookToken refers to the composition of the three path parts at the end of the WebHook URL (ie T12345678/B12345678/123456789012345678901234). A WebHookToken can be instantiated in several ways:

// Builder
WebHookToken token = WebHookToken.builder()
// Static factory
WebHookToken token = WebHookToken.fromString("T12345678/B12345678/123456789012345678901234");
// Static factory with URL
WebHookToken token = WebHookToken.fromString("");
// Or from system environment variables:
WebHookToken token = WebHookToken.fromEnvironment();

Sending Messages

Create a MessageRequest via the builder pattern:

// Simple example
MessageRequest message = MessageRequest.builder()
                // SlackMarkdown string decoration is handled automatically in fields that require it,
                // so this is valid:
                // and passing in the raw decorated string is valid:
                // or lastly, just pass the undecorated string (also valid):
                .text("The simplest message")

Next, send your message using the SlackWebHookService and receive the result:

ResponseCode response = SlackWebHookService.with(token)

RoboSlack handles error responses through the ResponseCode class. Check your ResponseCode to see why a message may have failed to send.

Slack Date Formatting

RoboSlack supports Slack's Date formatting in fields that allow Slack Markdown.

See "Formatting Dates" section in the Slack Docs for more information.

The main advantage of the SlackDateTime format over simply formatting a Temporal into a String and sending that within the Slack message is that the SlackDateTime renders differently based on where and when the client is viewing it. For example, if the client views a SlackDateTime with Date granularity (that represents a point in time at the same day of the client) Slack will render it astoday, but when they view the same message again the following day, Slack will render the message as yesterday instead..

Any Temporal object alone doesn't have this dynamic advantage, and also don't respect clients' timezones as easily as the SlackDateTime will. If a client crosses a timezone and views a SlackDateTime again, it will be rendered according to their new location's timezone.

// Assuming you have some Temporal object (for example a ZonedDateTime)
ZonedDateTime now =;

// Create a new SlackDateTime for that Temporal
SlackDateTime slackDateTime = SlackDateTime.of(now);

// Then create a formatter for it using DateTimeFormatTokens
SlackDateTimeFormatter formatter = SlackDateTimeFormatter.of("sent {date} at {time}");

// Finally create a message containing the SlackDateTime
MessageRequest message = MessageRequest.builder()
                .text(String.format("This is a message with a SlackDateTime: %s",
// Which would dynamically render to (when read on a client at the same day):
//  This is a message with a SlackDateTime: sent today at 12:23PM

Using the SlackDateTime.of() method, input a Temporal (and optionally a hyperlink reference for the generated text). Be sure to use a Temporal that contains all of the necessary Time/Date fields for proper rendering according to this table:

DateTimeFormatToken Format Description Valid Temporal types to use
{date} MMMMM dd, yyyy Long month name, day with ordinal, and year Instant, *Date, *DateTime (ie. OffsetDate or ZonedDateTime)
{date_num} yyyy-mm-dd All numbers, with leading zeroes Instant, *Date, *DateTime (ie. OffsetDate or ZonedDateTime)
{date_short} MMM dd, yyyy Short month name, day (no ordinal), and year Instant, *Date, *DateTime (ie. OffsetDate or ZonedDateTime)
{date_long} eeee, MMMM dd, yyyy Day of week, long month name, day with ordinal, and year Instant, *Date, *DateTime (ie. OffsetDate or ZonedDateTime)
{date_pretty} MMMM dd, yyyy Like DATE but uses yesterday, today, tomorrow when appropriate Instant, *Date, *DateTime (ie. OffsetDate or ZonedDateTime)
{date_short_pretty} MMM dd, yyyy Like DATE_SHORT but uses yesterday, today, tomorrow when appropriate Instant, *Date, *DateTime (ie. OffsetDate or ZonedDateTime)
{date_long_pretty} eeee, MMMMM dd, yyyy Like DATE_LONG but uses yesterday, today, tomorrow when appropriate Instant, *Date, *DateTime (ie. OffsetDate or ZonedDateTime)
{time} kk:mm 12/24 hour : minute, AM/PM if client configured for 12-hour time Instant, *Time (ie. LocalTime)
{time_secs} kk:mm:ss 12/24 hour : minute : second, AM/PM if client configured for 12-hour time Instant, *Time (ie. LocalTime)

For more information, see the Java DateTime API Pages. Use any combination of these DateTimeFormatTokens to display the Date or Time as needed.

If you supply a Temporal that doesn't support all of the required for your DateTimeFormatToken, or that isn't convertible to an Epoch Timestamp as Slack requires, RoboSlack will throw an IllegalArgumentException and won't proceed with parsing your message.


Looking to build upon RoboSlack? Come join us in our RoboSlack Slack Channel!


This project is made available under the Apache 2.0 License.


A pluggable, fluent, straightforward Java library for interacting with Slack.





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