# Java/Kotlin

{% hint style="info" %}
Java/Kotlin SDK supports JDK 8 and above.
{% endhint %}

## Add Dependency

[![](https://img.shields.io/maven-central/v/io.hackle/hackle-server-sdk)](https://central.sonatype.com/artifact/io.hackle/hackle-server-sdk)

Add the SDK dependency.

```groovy
repositories {
  mavenCentral()
}

dependencies {
  implementation 'io.hackle:hackle-server-sdk:2.32.0'
}
```

## SDK Initialization

{% hint style="danger" %}
HackleClient must be a singleton.

`HackleClient` manages state internally to assign Variations without blocking the calling thread.\
This requires additional resources.

It should be managed as a single instance throughout the application lifecycle rather than being instantiated for each request.
{% endhint %}

`HackleClient` is a class that provides methods for using the SDK features.

`HackleClient` initialization is required to use the SDK.

#### Instantiation

Pass the SDK Key to instantiate `HackleClient`.\
`HackleClient` periodically synchronizes with the Hackle server as a background task to obtain the required information.

* You can find the SDK Key in [SDK Integration Info](https://dashboard.hackle.io/config/sdk-setting) on the Hackle Service Dashboard.

{% tabs %}
{% tab title="Kotlin" %}

```kotlin
import io.hackle.sdk.HackleClient
import io.hackle.sdk.HackleClients

// Replace YOUR_SERVER_SDK_KEY with the SDK Key.
val hackleClient = Hackle.client(YOUR_SERVER_SDK_KEY)
```

{% endtab %}

{% tab title="Java" %}

```java
import io.hackle.sdk.HackleClient
import io.hackle.sdk.HackleClients

// Replace YOUR_SERVER_SDK_KEY with the SDK Key.
HackleClient hackleClient = HackleClients.create(YOUR_SERVER_SDK_KEY);
```

{% endtab %}
{% endtabs %}

## Shutdown

You must call the `close()` method when the application shuts down. This releases resources in use and sends any remaining events.

{% hint style="danger" %}
If the application exits without calling `close()`, **events may be lost.**
{% endhint %}

{% tabs %}
{% tab title="Kotlin" %}

```kotlin
import io.hackle.sdk.HackleClient

hackleClient.close()
```

{% endtab %}

{% tab title="Java" %}

```java
import io.hackle.sdk.HackleClient

hackleClient.close();
```

{% endtab %}
{% endtabs %}

#### If you are using Spring Framework

The best approach is to register `HackleClient` as a bean.\
It will be managed as a single instance throughout the application lifecycle, and `close()` will be called automatically when the application shuts down.

#### If you are wrapping HackleClient

It is recommended to implement `AutoClosable` in your wrapping class and call `HackleClient`'s `close()` when the wrapper's `close()` is called.

{% tabs %}
{% tab title="Kotlin" %}

```kotlin
import io.hackle.sdk.HackleClient

class CustomHackleClient(private val hackleClient: HackleClient): AutoCloseable {

    override fun close() {
        hackleClient.close()
    }
}
```

{% endtab %}

{% tab title="Java" %}

```java
import io.hackle.sdk.HackleClient

public class CustomHackleClient implements AutoCloseable {

    private final HackleClient hackleClient;

    public CustomHackleClient(HackleClient hackleClient) {
        this.hackleClient = hackleClient;
    }

    @Override
    public void close() throws Exception {
        hackleClient.close();
    }
}
```

{% endtab %}
{% endtabs %}


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