Step 1: Create a Blank SBT Project
Create a new directory for your project and navigate to it in your terminal.
Create a build.sbt file in the project directory and add the following content:
name := "todo-api"
version := "1.0"
scalaVersion := "2.13.8"
libraryDependencies ++= Seq(
"com.typesafe.play" %% "play-json" % "2.9.4",
"com.typesafe.play" %% "play-slick" % "5.0.0",
"com.typesafe.play" %% "play-slick-evolutions" % "5.0.0",
"org.postgresql" % "postgresql" % "42.2.14",
"com.typesafe.play" %% "play-guice" % "2.8.8",
"com.typesafe.play" %% "play" % "2.8.8"
)
Create a project/plugins.sbt file with the following content:
addSbtPlugin("com.typesafe.play" % "sbt-plugin" % "2.8.8")
Create a project/build.properties file with the following content:
sbt.version=1.5.5
Once we're done with this tutorial your file structure should look like this:
todo-api/
├── app/
│ ├── controllers/
│ │ └── TodoController.scala
│ ├── models/
│ │ └── Todo.scala
├── conf/
│ ├── application.conf
│ └── routes
├── project/
│ ├── build.properties
│ └── plugins.sbt
├── .gitignore
└── build.sbt
Step 2: Configure the Database
Create a PostgreSQL database and remember the connection details (URL, username, and password).
Open the conf/application.conf file and configure the database connection:
db.default.driver = org.postgresql.Driver
db.default.url = "jdbc:postgresql://localhost:5432/your_database_name"
db.default.username = your_username
db.default.password = "your_password"
Step 3: Define the Model
Create a models package in your project's app directory.
Inside the models package, create a Todo.scala file to define the "TODO" model:
package models
import play.api.libs.json._
case class Todo(id: Option[Long], task: String, completed: Boolean)
object Todo {
implicit val todoFormat: OFormat[Todo] = Json.format[Todo]
}
Step 4: Create the Controller
Create a controllers package in your project's app directory.
Inside the controllers package, create a TodoController.scala file to implement the API endpoints:
package controllers
import javax.inject.Inject
import play.api.libs.json._
import play.api.mvc._
import models.Todo
import play.api.db.slick.DatabaseConfigProvider
import slick.jdbc.JdbcProfile
import scala.concurrent.{ExecutionContext, Future}
class TodoController @Inject()(
dbConfigProvider: DatabaseConfigProvider,
cc: ControllerComponents
)(implicit ec: ExecutionContext)
extends AbstractController(cc) {
import profile.api._
private val dbConfig = dbConfigProvider.get[JdbcProfile]
private class TodoTable(tag: Tag) extends Table[Todo](tag, "todos") {
def id = column[Option[Long]]("id", O.PrimaryKey, O.AutoInc)
def task = column[String]("task")
def completed = column[Boolean]("completed")
def * = (id, task, completed) <> ((Todo.apply _).tupled, Todo.unapply)
}
private val todos = TableQuery[TodoTable]
def createTodo: Action[JsValue] = Action.async(parse.json) { implicit request =>
val todoResult = request.body.validate[Todo]
todoResult.fold(
errors => {
Future(BadRequest(Json.obj("message" -> JsError.toJson(errors))))
},
todo => {
val insertQuery = (todos returning todos.map(_.id)) += todo
dbConfig.db.run(insertQuery).map { id =>
Created(Json.obj("id" -> id, "task" -> todo.task, "completed" -> todo.completed))
}
}
)
}
def getAllTodos: Action[AnyContent] = Action.async { _ =>
val query = todos.result
dbConfig.db.run(query).map { todos =>
Ok(Json.toJson(todos))
}
}
def getTodoById(id: Long): Action[AnyContent] = Action.async { _ =>
val query = todos.filter(_.id === Some(id)).result.headOption
dbConfig.db.run(query).map {
case Some(todo) => Ok(Json.toJson(todo))
case None => NotFound
}
}
def updateTodo(id: Long): Action[JsValue] = Action.async(parse.json) { implicit request =>
val todoResult = request.body.validate[Todo]
todoResult.fold(
errors => {
Future(BadRequest(Json.obj("message" -> JsError.toJson(errors))))
},
updatedTodo => {
val updateQuery = todos.filter(_.id === Some(id)).map(todo => (todo.task, todo.completed)).update((updatedTodo.task, updatedTodo.completed))
dbConfig.db.run(updateQuery).map {
case 0 => NotFound
case _ => Ok(Json.toJson(updatedTodo))
}
}
)
}
def deleteTodoById(id: Long): Action[AnyContent] = Action.async { _ =>
val deleteQuery = todos.filter(_.id === Some(id)).delete
dbConfig.db.run(deleteQuery).map {
case 0 => NotFound
case _ => NoContent
}
}
}
In this code:
The TodoController class defines endpoints for creating, retrieving, updating, and deleting TODO items.
It uses Play Framework's JSON serialization/deserialization to work with JSON data.
It uses Slick for database interactions.
Step 5: Configure Routes
Create a conf/routes file in your project's conf directory if it doesn't already exist.
Inside the routes file, define the routes for your API endpoints. Here's an example for the TodoController:
# Routes
# This file defines all application routes (Higher priority routes first)
# ~~~~
# Home page
GET / controllers.HomeController.index
# Define routes for the TodoController
GET /todos controllers.TodoController.getAllTodos
POST /todos controllers.TodoController.createTodo
GET /todos/:id controllers.TodoController.getTodoById(id: Long)
PUT /todos/:id controllers.TodoController.updateTodo(id: Long)
DELETE /todos/:id controllers.TodoController.deleteTodoById(id: Long)
In the routes file:
You define routes for various HTTP methods (GET, POST, PUT, DELETE) and associate them with controller methods in the format controllers.ControllerName.methodName(arguments).
For example, GET /todos maps to the getAllTodos method in the TodoController.
The :id syntax in routes indicates a dynamic parameter that will be passed to the controller method.
By configuring the routes file, you specify how incoming requests are routed to the appropriate controller actions. This file is a crucial part of your Play Framework application's configuration.
Step 6: Run the Application
Start the Play Framework application by running the following command in your project directory:
sbt run
Access the API endpoints at http://localhost:9000/todos.
You've now created a CRUD JSON API in Scala using the Play Framework with PostgreSQL integration. You can test your API using tools like Postman or curl.
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