swift-okhttp

June 4, 2026 · View on GitHub

Swift bindings for OkHttp, generated with swift-java, plus an OpenAPIOkHttp transport implementing ClientTransport for Swift OpenAPI.

It lets Swift code use OkHttp as its HTTP client. The primary motivation is Swift on Android. This package gives Swift-on-Android code a robust, idiomatic HTTP client by bridging directly to OkHttp.

It also works on any other host with a Java runtime (e.g. desktop/server JVM on macOS or Linux), which is how the SampleApp runs.

Important

OkHttp is a Java library. This package calls into it over JNI (via swift-java), so it needs a Java runtime and the OkHttp classes available at runtime. On Android both are already part of the app (the ART runtime plus OkHttp as a normal Gradle dependency); your Swift code is compiled to native and loaded into the app process. This is not a pure-Swift, standalone HTTP client. See Requirements and How it works.

Requirements

Swift 6.2+
A Java runtime with the matching OkHttp version on the classpath (see Choosing the OkHttp version):
- Android — the primary target; OkHttp ships as a standard implementation dependency.
- Desktop/server JVM — a JDK (the SampleApp targets JDK 21) with OkHttp on the classpath.

Products

OkHttp — generated Swift wrappers over the OkHttp API.
OpenAPIOkHttp — OkHttpClientTransport, a ClientTransport for swift-openapi-runtime backed by OkHttp.

Installation

.package(url: "https://github.com/frameo-net/swift-okhttp", from: "0.1.0")

.target(
    name: "MyTarget",
    dependencies: [
        .product(name: "OpenAPIOkHttp", package: "swift-okhttp"),
        // or .product(name: "OkHttp", package: "swift-okhttp")
    ]
)

Choosing the OkHttp version

swift-okhttp ships wrappers for two OkHttp major versions, selected with a SwiftPM package trait:

Build	OkHttp version	Runtime jar you must provide
default (no trait)	5.x (`5.3.2`)	`com.squareup.okhttp3:okhttp:5.x`
`OkHttp4` trait enabled	4.x (`4.12.0`)	`com.squareup.okhttp3:okhttp:4.x`

OkHttp 5 is the default. To use OkHttp 4 instead, enable the OkHttp4 trait on the dependency:

.package(url: "https://github.com/frameo-net/swift-okhttp", from: "0.1.0", traits: ["OkHttp4"])

Important

The trait only chooses which Swift wrappers compile. The actual OkHttp jar comes from your runtime classpath (e.g. your Android/Gradle dependency), which SwiftPM cannot control. The trait and the jar must match — pairing the OkHttp4 trait with a 5.x jar (or vice versa) compiles fine but fails at runtime with NoSuchMethodError/ClassNotFoundException.

Usage

Using the OpenAPI transport:

import OkHttp
import OpenAPIOkHttp

let client = OkHttpClient()
let transport = OkHttpClientTransport(
    configuration: .init(client: client)
)
let apiClient = try Client(serverURL: Servers.Server1.url(), transport: transport)
let response = try await apiClient.getRequest()

See SampleApp for a complete, runnable example, including the Gradle wiring that loads the compiled Swift dynamic library into a JVM and puts OkHttp on the classpath.

How it works

swift-java generates Swift wrappers for OkHttp's Java classes and bridges calls over JNI. At runtime the Swift code runs inside a Java runtime that has OkHttp on its classpath.

On Android, that runtime is the app's ART process: your Swift code is cross-compiled to a native library and loaded into the app, and OkHttp is already available as a normal Gradle dependency — so there is nothing extra to ship.

The SampleApp demonstrates the same mechanism on a desktop JVM: the Swift package is built as a dynamic library, loaded with System.loadLibrary(...) from a Java entry point, with OkHttp supplied as a normal JVM dependency.

Regenerating the wrappers

The Swift wrappers are committed and checked in, one set per OkHttp version:

Sources/OkHttp/
  OkHttp.swift            # hand-written; keeps the target non-empty
  swift-java.v4.config    # class list + OkHttp 4 dependency
  swift-java.v5.config    # class list + OkHttp 5 dependency
  v4/*.v4.swift           # generated, guarded by #if OkHttp4
  v5/*.v5.swift           # generated, guarded by #if !OkHttp4

To regenerate (e.g. to bump an OkHttp version in the relevant swift-java.v*.config):

./scripts/generate-wrappers.sh

The script is the single source of truth: you can delete Sources/OkHttp/v4 and Sources/OkHttp/v5 entirely, run it, and the project compiles again. For each version it resolves the classpath, runs swift-java wrap-java, applies the necessary post-processing (removing a duplicate close() and the synthetic access$…$cp accessors), then wraps each file in its trait #if guard and writes it into the versioned directory. Do not hand-edit the generated files — add any fix to the script instead.

License

swift-okhttp is released under the MIT License. It wraps and depends on third-party software under their own licenses — see NOTICE.md.