How to Upgrade from STTP Client 3 to Client 4 in Scala

Upgrading an application to a new version of a library often comes with a host of benefits, including improved performance and features. If you're working with Scala and using the STTP (Scala HTTP client) library, you might be looking to upgrade from STTP Client 3 to STTP Client 4. In this article, we will explore how to successfully execute this upgrade, particularly keeping in mind the syntax and API differences that may arise during the migration process.

Understanding the Need for Upgrade

STTP Client 4 offers several enhancements over its predecessor, including a more streamlined API that emphasizes simplicity and flexibility. One common issue developers face during this transition is ensuring that their requests are properly adapted to work with the new client architecture. If you are facing the challenge where your existing code:

SttpClientInterpreter().toRequest(endpoint, url).apply("foo")

returns client3.Request[DecodeResult[Either[E, O]], R], you are not alone. Let's break down how you can effectively move to Client 4 and remedy this situation.

Step 1: Update Your Dependencies

Before jumping into the code changes, ensure that your project's build file (e.g., build.sbt for SBT) reflects the latest version of STTP. For instance:

libraryDependencies += "com.softwaremill.sttp.client4" %% "core" % "4.x.x"

Replace 4.x.x with the latest version at your time of writing.

Step 2: Modify Your Code for Client 4

The next step involves adapting your code to use the new features present in STTP Client 4. The method to convert endpoints into requests has been restructured slightly. Instead of using SttpClientInterpreter, you can utilize the new sttp.client4 imports.

Here is an updated example of how to construct a request with STTP Client 4:

Converting Requests in STTP Client 4

You can utilize the basicRequest constructor instead of relying on SttpClientInterpreter. Here’s how you can redo your request:

import sttp.client4._
import sttp.model.Uri

val endpoint: Uri = uri"http://example.com/api"
val request = basicRequest
  .get(endpoint)
  .header("Content-Type", "application/json")

val response = request.send(backend)

Step 3: Manage Responses Properly

With STTP Client 4, handling responses has also been updated. It is crucial to manage the response accordingly. You might want to pattern match the response to safely handle both success and failure cases:

response.map { res =>
  res.body match {
    case Right(data) => println(s"Success: $data")
    case Left(error) => println(s"Error: $error")
  }
}

This ensures you're utilizing the more robust error handling mechanisms present in STTP Client 4.

Frequently Asked Questions (FAQ)

What is the main benefit of upgrading to STTP Client 4?

Upgrading to STTP Client 4 allows you to leverage the improved API, more efficient handling of requests and responses, and additional features that facilitate asynchronous programming environments.

Are there any breaking changes?

There are breaking changes when transitioning from Client 3 to Client 4. Familiarize yourself with the official migration guide to smooth out the upgrade process.

Can I use my existing code as-is after upgrading?

No, you will need to modify your existing code to conform to the new STTP Client 4 structures and methods as demonstrated above.

Conclusion

Upgrading from STTP Client 3 to Client 4 may require some adjustments in your code, especially around request and response handling. Follow the steps outlined above to ensure that your application can take full advantage of the new features and improvements offered by STTP Client 4. By doing so, you'll ensure smoother HTTP communication and a better overall development experience in your Scala applications.