This documentation is very much a work in progress. Expected completion is November 2022.

Introduction

Jarvis is an HTTP server that makes it easy to create a web service to provide access to your APL code from the web or a local network.

Any client program written in any language on any platform that can process HTTP requests can access a Jarvis-based web service. This vastly increases the potential audience for your application - the client can be a standard web browser, a phone app, a browser-based app, or a custom client written in a language like Python or C# and yes, even APL.

The name Jarvis is a pseudo-acronym for JSON and REST Service ("vice" becomes "vis") and was also inspired by J.A.R.V.I.S. (Just A Rather Very Intelligent System) from the Marvel Cinematic Universe.

Design Goals

Jarvis is designed to make it very easy for an APLer to create web services without requiring in-depth knowledge of web service frameworks. In designing Jarvis we've attempted to

Make Jarvis' default behavior simple and applicable to many use cases
Make few assumptions about what the user actually needs to do
Provide hooks to allow the user to tailor or extend Jarvis' behavior if needed

Create an APL Web Service in 5 Minutes

If you know how to write a monadic, result-returning APL function, you're ready to run your first Jarvis-based web service. Here's how:

If you already have a copy of the Jarvis class, skip to step 3. Otherwise, load the HttpCommand utility so that we can download a copy of Jarvis and also use HttpCommand for testing our web service.
```
      ]load HttpCommand
```
Next, download a copy of Jarvis. Note, the following statement simply downloads the latest, perhaps pre-release, version of the Jarvis class for this quick demonstration. For a production environment, you should use a released version of Jarvis. HttpCommand.Fix both downloads and runs ⎕FIX on an APL code file from the web.
```
      HttpCommand.Fix 'https://raw.githubusercontent.com/Dyalog/Jarvis/master/Source/Jarvis.dyalog
```

Write one or more monadic, result-returning APL functions. For instance:

      )cs #
      sum ← {+/⍵}                       ⍝ dfns work
      total ← +/                        ⍝ derived functions work
      ⎕FX '∇r←addemup a' 'r←+/a' '∇'    ⍝ and of course, tradfns work

You can now run your web service running on port 8080 and serving code from the # (root) namespace.

      (server rc)←Jarvis.Run 8080 #
2021/11/22 @ 15:12:06 - Conga copied from C:\Program Files\Dyalog\Dyalog APL-64 18.2 Unicode/ws/conga
2021/11/22 @ 15:12:06 - Local Conga reference is #.Jarvis.[LIB]
2021/11/22 @ 15:12:06 - Jarvis started in "JSON" mode on port 8080
2021/11/22 @ 15:12:06 - Serving code in #
2021/11/22 @ 15:12:06 - Click http://localhost:8080 to access web interface

If the server started successfully, you'll see messages similar to those above and server will be a reference to the server instance and the return code rc should be 0.

Now, let's test our service using Jarvis' built-in HTML interface. You could click on the link displayed or open your favorite browser to http://localhost:8080, but just for fun, we'll use Dyalog's HTMLRenderer object.

       'h' ⎕WC 'HTMLRenderer' ('URL' 'localhost:8080')

Jarvis Sample

We select the Endpoint (APL function) we want from the drop down list, enter some valid JSON data ([1,3,5]), and press Send to send the request to Jarvis. Jarvis' response is then sent back and displayed.

We can also use HttpCommand to call the web service.

      (url data headers)←'localhost:8080/total' '[1,3,5]' ('content-type' 'application/json')
      (HttpCommand.Do 'POST' url data headers).Data
9

We can use the cURL command to call the web service.

C:\> curl -H "content-type: application/json" -X POST -d [1,3,5] http://localhost:8080/addemup
9

To stop the service, simply type server.stop

Interested? Read on...