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API Client Installation

The first step to using the Slack API client is installing the slack-api-client module. This guide shows you how to set up using Maven, Gradle, or by building from source on your own.

Prerequisites​

Installing OpenJDK 8 or higher LTS version beforehand is required. As long as you are using a supported JDK version, this SDK should work with any OpenJDK distributions.

Maven​

As slack-api-client is a library dependency, there is no requirement of Maven versions.

pom.xml​

Save pom.xml with the following XML definition in the root directory of your Java project. As you see, this is a commonplace Maven project. No specific settings are needed to load the project on your favorite IDE.

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>awesome-slack-app</artifactId>
  <version>0.1-SNAPSHOT</version>
  <packaging>jar</packaging>
  <properties>
    <maven.compiler.target>1.8</maven.compiler.target>
    <maven.compiler.source>1.8</maven.compiler.source>
  </properties>
  <dependencies>
    <dependency>
      <groupId>com.slack.api</groupId>
      <artifactId>slack-api-client</artifactId>
      <version>1.45.3</version>
    </dependency>
  </dependencies>
</project>

src/main/java/Example.java​

Create a new Java class named Example that has a main method to run. Place the following code in the method for verifying the build settings are valid.

import com.slack.api.Slack;
import com.slack.api.methods.response.api.ApiTestResponse;

public class Example {
  public static void main(String[] args) throws Exception {
    Slack slack = Slack.getInstance();
    ApiTestResponse response = slack.methods().apiTest(r -> r.foo("bar"));
    System.out.println(response);
  }
}

Run the Example.main(String[]) method from your IDE or by running the following command in your terminal.

mvn compile exec:java \
  -Dexec.cleanupDaemonThreads=false \
  -Dexec.mainClass="Example"

If you see the following stdout, your installation has succeeded!

ApiTestResponse(ok=true, args=ApiTestResponse.Args(foo=bar, error=null), warning=null, error=null, needed=null, provided=null)

In summary, the things you've done here are:

  • ✅ Installed JDK 8 or higher (if not, run brew install openjdk@11 for macOS / visit OpenJDK website for others)
  • ✅ Installed Maven (if not, run brew install maven for macOS / visit their website for others)
  • ✅ Updated the pom.xml file to have slack-api-client as a dependency
  • ✅ Added a main method to the src/main/java/Example.java file

Gradle​

If you prefer using Gradle, the steps are similar to Maven, but there are some differences.

build.gradle​

Place build.gradle in the root directory of your Java project. We don't have any requirements for Gradle versions.

plugins {
  id("application")
}
repositories {
  mavenCentral()
}
dependencies {
  implementation("com.slack.api:slack-api-client:1.45.3")
}
application {
  mainClassName = "Example"
}

As with Maven, create a class named Example with a main method. Then, run it from your IDE or execute the gradle run command in your terminal. You'll see the same stdout.

In summary, the things you've done here are:

  • ✅ Installed JDK 8 or higher (if not, run brew install openjdk@11 for macOS / visit OpenJDK website for others)
  • ✅ Installed Gradle (if not, run brew install gradle for macOS / visit their website for others)
  • ✅ Added build.gradle to have slack-api-client as a dependency
  • ✅ Added a main method to the src/main/java/Example.java file

Gradle for Kotlin​

In this guide, we sometimes use Kotlin code examples for simplicity. To try those examples, set up a Kotlin project with Gradle as below.

build.gradle​

The build settings are almost the same as above except for some Kotlin-specific parts.

plugins {
  id("org.jetbrains.kotlin.jvm") version "1.7.21" // use the latest Kotlin version
  id("application")
}
repositories {
  mavenCentral()
}
dependencies {
  implementation(platform("org.jetbrains.kotlin:kotlin-bom"))
  implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
  implementation("com.slack.api:slack-api-client:1.45.3")

  // Add these dependencies if you want to use the Kotlin DSL for building rich messages
  implementation("com.slack.api:slack-api-model-kotlin-extension:1.45.3")
  implementation("com.slack.api:slack-api-client-kotlin-extension:1.45.3")
}
application {
  mainClassName = "ExampleKt" // add "Kt" suffix for main function source file
}

src/main/kotlin/Example.kt​

As you see, the code using slack-api-client in Kotlin is much more concise than in Java. Run the following code from your IDE or by executing the gradle run command in your terminal.

import com.slack.api.Slack

fun main() {
  val slack = Slack.getInstance()
  val response = slack.methods().apiTest { it.foo("bar") }
  println(response)
}
Tip

A name of a source file in Kotlin needs to end with .kt, not .java.

In summary, the things you've done here are:

  • ✅ Installed JDK 8 or higher (if not, run brew install openjdk@11 for macOS / visit OpenJDK website for others)
  • ✅ Installed Gradle (if not, run brew install gradle for macOS / visit their website for others)
  • ✅ Updated build.gradle to have valid Kotlin language settings and slack-api-client as a dependency
  • ✅ Added a main method to the src/main/kotlin/Example.kt file

Build from source​

You may want to build the latest revision on your own. In the case of building from source, execute the following commands in your terminal.

git clone git@github.com:slackapi/java-slack-sdk.git
cd java-slack-sdk
mvn install -Dmaven.test.skip=true

All of the SDK modules will be available under $HOME/.m2/repository, so that you can now use them on the machine. If you're using Gradle, make sure to add mavenLocal() to repositories in your build.gradle.

repositories {
  mavenLocal()
}