Kotlin Support

Kotlin is a statically-typed language targeting the JVM (and other platforms), enabling concise and elegant code with seamless interoperability with Java libraries. LangChain4j utilizes Kotlin extensions and type-safe builders to enhance Java APIs with Kotlin-specific conveniences. This allows users to extend existing Java classes with additional functionality tailored for Kotlin.

note

LangChain4j does not require Kotlin libraries as runtime dependencies but allows users to leverage Kotlin's coroutine capabilities for non-blocking execution, enhancing performance and efficiency.

ChatLanguageModel Extensions

This Kotlin code demonstrates how to use coroutines and suspend functions and type-safe builders to interact with a ChatLanguageModel in LangChain4j.

val model = OpenAiChatModel.builder()
    .apiKey("YOUR_API_KEY")
    // more configuration parameters here ...
    .build()

CoroutineScope(Dispatchers.IO).launch {
    val response = model.chat {
        messages += systemMessage("You are a helpful assistant")
        messages += userMessage("Hello!")
        parameters {
            temperature = 0.7
        }
    }
    println(response.aiMessage().text())
}

The interaction happens asynchronously using Kotlin's coroutines:

• CoroutineScope(Dispatchers.IO).launch: Executes the process on the IO dispatcher, optimized for blocking tasks like network or file I/O. This ensures responsiveness by preventing the calling thread from being blocked.
• model.chat is a suspend function, that uses a builder block to structure the chat request. This approach reduces boilerplate and makes the code more readable and maintainable.

For advanced scenarios, to support custom ChatRequestParameters, type-safe builder function accepts custom builder:

fun <B : DefaultChatRequestParameters.Builder<*>> parameters(
    builder: B = DefaultChatRequestParameters.builder() as B,
    configurer: ChatRequestParametersBuilder<B>.() -> Unit
)

Example usage:

 model.chat {
    messages += systemMessage("You are a helpful assistant")
    messages += userMessage("Hello!")
    parameters(OpenAiChatRequestParameters.builder()) {
        temperature = 0.7 // DefaultChatRequestParameters.Builder property
        builder.seed(42) // OpenAiChatRequestParameters.Builder property
    }
}