Let's create our controller com.packt.microservices.geolocation.GeoLocationController.java with a stubbed-out GET API:

      package com.packt.microservices.geolocation; 
 
      import static spark.Spark.*; 
 
      public class GeoLocationController { 
 
        public static void main(String[] args) { 
          get("/geolocation", (req, resp) -> "[]"); 
        } 
      } 

The quickest way to test this is by running this class as a Java application. If you get SLF4J errors in your console after you start the application, add the following Maven dependency to your pom.xml file and restart your application:

      <dependency> 
        <groupId>org.slf4j</groupId> 
        <artifactId>slf4j-simple</artifactId> 
        <version>1.7.21</version> 
      </dependency> 

The slf4j-simple dependency routes all the SLF4Jlog messages to the System.err stream.

Your console logs should look something like this after the restart:

From the logs, we can clearly see that the service is running on port 4567.

Execute the following curl command in a terminal window to make sure our API is exposed. The response of the following command should be [], indicating there are no geolocations:

      curl http://localhost:4567/geolocation

Now let's finish building the APIs. We already have a very basic stubbed-out GET API. Let's just introduce the service class to the controller and call the findAll method. Similarly, let's use the service's create method for POST API calls. Before we do that, we need to do one more thing. By default, SparkJava does not perform JSON serialization and deserialization. We will be using a library called gson to do that. So add the following dependency to your pom.xml file:

        <dependency>
          <groupId>com.google.code.gson</groupId>
          <artifactId>gson</artifactId>
          <version>2.7</version>
        </dependency>

Now let's replace the main method of GeoLocationController.java with this:

    public static void main(String[] args) {
      GeoLocationService service = new GeoLocationServiceImpl();
      Gson gson = new Gson();
    
      get("/geolocation", (req, resp) -> {
        return service.findAll();
      }, gson::toJson);
    
      post("/geolocation", (req, resp) -> {
        return service.create(gson.fromJson(req.body(), GeoLocation.class));
      }, gson::toJson);
    }

Execute the following cURL commands in your terminal one by one:

        curl -H "Content-Type: application/json" -X POST -d '{"timestamp": 1468203975, "userId": "f1196aac-470e-11e6-beb8-9e71128cae77", "latitude": 41.803488, "longitude": -88.144040}' http://localhost:4567/geolocation

This should give you an output similar to the following (pretty-printed for readability):

        {
          "latitude": 41.803488,
          "longitude": -88.14404,
          "userId": "f1196aac-470e-11e6-beb8-9e71128cae77",
          "timestamp": 1468203975
        }

        curl -H "Content-Type: application/json" -X POST -d '{"timestamp": 1468203975, "userId": "f1196aac-470e-11e6-beb8-9e71128cae77", "latitude": 9.568012, "longitude": 77.962444}' http://localhost:4567/geolocation

This should give you an output like this (pretty-printed for readability):

        {
          "latitude": 9.568012,
          "longitude": 77.962444,
          "userId": "f1196aac-470e-11e6-beb8-9e71128cae77",
          "timestamp": 1468203975
        }

To verify whether your entities were stored correctly, execute the following cURL command:

      curl http://localhost:4567/geolocation

It should give you output similar to the following (pretty-printed for readability):

        [
          {
            "latitude": 41.803488,
            "longitude": -88.14404,
            "userId": "f1196aac-470e-11e6-beb8-9e71128cae77",
            "timestamp": 1468203975
          },
          {
            "latitude": 9.568012,
            "longitude": 77.962444,
            "userId": "f1196aac-470e-11e6-beb8-9e71128cae77",
            "timestamp": 1468203975
          }
       ]