Fix #257: Return http.Handler instead of SetupRouter in server/restapi/web

[Arjunmehta312]

Description

Fixes #257

This PR addresses the issue raised by @rakyll to return an http.Handler instead of requiring users to pass in a *mux.Router. This change follows Go best practices by decoupling the REST API implementation from a specific router library (gorilla/mux).

Changes

1. Added NewHandler() function (server/restapi/web/server.go)

• Created NewHandler(config *adk.Config) http.Handler that returns a standard http.Handler
• This is now the preferred way to integrate ADK REST API with any HTTP server
• Users can register the handler with any router: standard net/http.ServeMux, chi, echo, gin, etc.

2. Maintained backward compatibility

• Kept existing SetupRouter() function fully functional
• Marked it as Deprecated with clear migration guidance
• No breaking changes for existing code

3. Updated internal usage (cmd/launcher/web/api/api.go)

• Refactored SetupSubrouters() to use NewHandler() internally
• Applied CORS middleware before registration
• Uses http.StripPrefix for proper path handling

4. Added example (examples/restapi/main.go)

• Demonstrates usage with standard net/http.ServeMux
• Shows how to compose the handler with other endpoints
• Proves the framework-agnostic approach works

Benefits

• Decoupled: Not tied to gorilla/mux or any specific router
• Flexible: Works with any HTTP server implementation
• Standard: Returns http.Handler, following Go conventions
• Backward Compatible: Existing code continues to work
• Easy Migration: Clear deprecation notice with alternative

Testing

• All packages build successfully: go build ./...
• No breaking changes to existing functionality
• Example runs and demonstrates new usage pattern
• No existing code in the repository uses the old pattern directly

Migration Guide

Before (old approach):

router := mux.NewRouter()
restapiweb.SetupRouter(router, config)

After (new approach):

handler := web.NewHandler(config)
mux.Handle("/api/", http.StripPrefix("/api", handler))

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Summary of Changes

Hello @Arjunmehta312, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant refactoring to the ADK REST API server setup, moving from a gorilla/mux-specific router configuration to a more generic http.Handler interface. This change enhances the flexibility and modularity of the API, allowing it to be integrated seamlessly with any Go HTTP server or routing library. The update also includes a new example showcasing this improved integration.

Highlights

• API Handler Refactor: The server/restapi/web package now provides a NewHandler function that returns a standard http.Handler, promoting router-agnostic integration.
• gorilla/mux Decoupling: The previous SetupRouter function is deprecated, reducing the tight coupling to the gorilla/mux router.
• New Example: A new example (examples/restapi/main.go) demonstrates how to use the new http.Handler with the standard net/http package.

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[Arjunmehta312]

Made the required changes @dpasiukevich Please review and merge if proper. Thanks and regards.

[dpasiukevich]

@Arjunmehta312 could you also update the example to pass the linter and we're good to merge.

[Arjunmehta312]

Sure, will update the example to pass the linter as you mentioned

[Arjunmehta312]

@dpasiukevich done please check it out 😊

[Arjunmehta312]

Also please note that, as per maintainer feedback, the public SetupRouter() function has been removed entirely This is a breaking change but aligns with the goal of decoupling from gorilla/mux

All okay?

[Arjunmehta312]

Thanks @dpasiukevich , sorry for the multiple reviews.

Happy to contribute!