# OkHttp — Modern HTTP Client for Java and Kotlin

> A reliable and efficient HTTP client for the JVM and Android with connection pooling, transparent GZIP, response caching, and WebSocket support.

## Install

Save in your project root:

# OkHttp — Modern HTTP Client for Java and Kotlin

## Quick Use
```kotlin
val client = OkHttpClient()
val request = Request.Builder()
    .url("https://api.example.com/data")
    .build()
val response = client.newCall(request).execute()
println(response.body?.string())
```

## Introduction
OkHttp is an HTTP and HTTP/2 client by Square for Java and Kotlin applications. It handles connection pooling, request retries, and response caching transparently so developers can focus on application logic rather than networking boilerplate.

## What OkHttp Does
- Sends synchronous and asynchronous HTTP requests with a clean builder API
- Maintains a connection pool that reuses sockets across requests to reduce latency
- Supports HTTP/2 multiplexing and transparent GZIP compression
- Provides interceptors for logging, authentication, retries, and custom request modification
- Handles WebSocket connections for real-time bidirectional communication

## Architecture Overview
OkHttp is built around a dispatcher that manages a thread pool for async calls. Requests pass through a chain of interceptors (application-level then network-level) before reaching the connection layer. The connection pool keeps idle sockets alive for reuse, and a disk-based cache stores responses following HTTP caching semantics.

## Self-Hosting & Configuration
- Add via Gradle: implementation("com.squareup.okhttp3:okhttp:4.12.0")
- Configure timeouts with OkHttpClient.Builder (connectTimeout, readTimeout, writeTimeout)
- Add interceptors for logging via okhttp3-logging-interceptor module
- Set up certificate pinning with CertificatePinner for enhanced security
- Customize the connection pool size and keep-alive duration for high-throughput scenarios

## Key Features
- Transparent connection pooling reduces request latency by reusing TCP connections
- Interceptor chain allows modular request/response processing
- HTTP/2 support with graceful fallback to HTTP/1.1
- Built-in response caching that respects Cache-Control headers
- First-class Kotlin coroutine support via the suspending extension

## Comparison with Similar Tools
- **Java HttpClient (JDK 11+)** — built-in with no extra dependency but lacks interceptors and connection pool tuning
- **Apache HttpClient** — feature-rich but heavier API surface and slower to adopt modern protocols
- **Retrofit** — a higher-level REST client that uses OkHttp as its transport layer
- **Ktor Client** — Kotlin-native async client; better for pure Kotlin multiplatform projects

## FAQ
**Q: Does OkHttp work on Android?**
A: Yes. OkHttp is the default HTTP engine on Android and is used internally by the platform.

**Q: How do I add logging?**
A: Add the okhttp3-logging-interceptor dependency and attach an HttpLoggingInterceptor to your client builder.

**Q: Can I use OkHttp with coroutines?**
A: Yes. Use the Call.enqueue suspend extension or wrap calls with withContext(Dispatchers.IO).

**Q: What is the minimum Java version?**
A: OkHttp 4.x requires Java 8+ or Android API 21+.

## Sources
- https://github.com/square/okhttp
- https://square.github.io/okhttp/

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Source: https://tokrepo.com/en/workflows/ee9438ae-433e-11f1-9bc6-00163e2b0d79
Author: AI Open Source