edadma / energize   0.12.10

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Create a Rest API in Seconds

Scala versions: 2.12


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Create a Rest API in Seconds


Energize allows you to get your Rest API server and database up and running in very little time.


Energize is distributed under the ISC License, meaning that you are free to use it in your free or proprietary software.




If you just want to download the executable so that you can have an API server for your project or use the REPL, you can download it from here. You do not need the Scala library for it to work because the JAR already contains all dependencies. You just need Java 8+ installed.

Run it as a normal Java executable JAR with the command java -jar energize-0.12.4.jar <config> in the folder where you downloaded the file, where config is the name of the .energize file (without the file extension) that defines your API.


Use the following definition to use Energize in your Maven project:


Add the following to your build.sbt file to use Energize in your SBT project:

resolvers += "Hyperreal Repository" at "https://dl.bintray.com/edadma/maven"
libraryDependencies += "xyz.hyperreal" %% "energize" % "0.12.4"



  • Java 8 (any revision)
  • SBT 0.13.13+ (which then downloads Scala 2.12.x automatically)

Clone and Run the SBT (Simple Build Tool)

git clone git://github.com/vinctustech/energize.git
cd energize

SBT Commands

Once the SBT prompt appears, use the following commands.

  • test builds and executes tests
  • re-start <config> starts the server where config is the name of the .energize file (without the file extension) that defines your API. You can press ENTER once the server has started to get the SBT prompt in order to enter SBT commands while the server is running.
  • re-stop stops the server. The port will be unbound some time after the server process has been killed (on Linux).
  • runMain xyz.hyperreal.energize.REPLMain starts the REPL
  • run <config> this will also start the server, however, it is recommended to use re-start instead. Starting the server using run means that the JVM process that SBT is running in is the one that is bound to the port that the server is using, whereas using re-start causes the server to run in a separate process that can later be killed using re-stop.


This example shows how to get a simple API to support a "to do list" app working. Start by creating a folder for the example. Now download the executable and place it in the example folder you just created. Now, create a text file called todo.energize with the following text in it.

resource todo /api/v1
  name        string  required
  description string  optional
  status      integer required

The executable contains both an HTTP server and a REPL to make it easier to develop your API definitions. We'll start by looking at the server.

HTTP Server

Now, on the command line in the example folder, start the server with the command

java -jar energize-0.12.4.jar todo

You should now have a working HTTP server bound to port 8080 that will serve API requests for a todo list. Let's try it out. Using curl, let's add an item to our todo list database. To do that, type

curl -d "{name: \"finish 0.1\", status: 1}" http://localhost:8080/api/v1/todo

You should see

  "data": 1

as the response. This means that the route (URI) was correct and that one row was added to the database. Add another item by typing

curl -d "{name: \"write readme\", description: \"add example involving finishing 0.1 and writing the readme\", status: 1}" http://localhost:8080/api/v1/todo

We can see our todo list with the command

curl http://localhost:8080/api/v1/todo

getting the response

  "data": [
      "_id": 1,
      "name": "finish 0.1",
      "description": null,
      "status": 1
      "_id": 2,
      "name": "write readme",
      "description": "add example involving finishing 0.1 and writing the readme",
      "status": 1

The description is null in the first one because we marked that column as optional and did not provide data for it in our post. Also, notice that the property names are the column names originally provided in the configuration and not the case-insensitive uppercase names that are returned by the database (H2 by default). We can retrieve just the second item with the command

curl http://localhost:8080/api/v1/todo/2

to get

  "data": {
    "_id": 2,
    "name": "write readme",
    "description": "add example involving finishing 0.1 and writing the readme",
    "status": 1

Notice that with this response, the data field is not an array but a single object since the URI path is pointing to a single item within the todo resource. Lastly, if we try querying the server for an item that does not exist from a resource that does exist, we should get a 404 status code from the server because what is being requested doesn't exist. Try it

curl http://localhost:8080/api/v1/todo/3

Press Ctrl-C to stop the server.


To start the REPL (read, execute, print, loop), type the following command (while in the same folder where the executable was placed)

java -cp energize-0.12.4.jar xyz.hyperreal.energize.REPLMain

By default, the REPL creates an in-memory H2 database for you and connects to it. Type help to see all the REPL commands. Tell the REPL to load the todo configuration by typing

l todo

To verify that a table called todo has been created, type the SQL command

select * from todo;

To use your Postgres database specified in your database configuration instead type the following commands


In the REPL, you can always restart from scratch using the wipe command, reload a modified configuration using load, etc.