OkHttp Library

The top level is application layer, consisting of OkHttpClient, Request, Response, RealCall. It’s the entrance for developers and is the core builder that handles global configurations like timeout, caching and filtering. It’s also thread-safe singleton that is shared globally.

The scheduling layer consists of Dispatcher, ExecutorService that

• handles request concurrency and thread execution
• handles async task queue and supports concurrency control

The interceptor layer consists of series of interceptors. It’s based on chain of responsibility and process requests and responses layer by layer. The interceptors can also be customized. Overall, the interceptors can be categorized into application interceptor and network interceptor.

The connection layer contains Connection and ConnectionPool. It establishes and reuses TCP/TLS connection and supports keep-alive reusing to decrease handshake latency.

The IO layer contains Okio Stream, Socket and Server that is responsible for low-level networking IO and encrypted communication.