Star Wars API Client Lab 🚀¶

In this hands-on lab, you'll build a Java client for the Star Wars API (SWAPI) with the help of GitHub Copilot! This lab demonstrates how GitHub Copilot can assist with creating DTOs, interfaces, implementations, and tests.

Lab Overview 📋¶

Duration: 1 hour
Difficulty: Intermediate
Prerequisites:

Basic knowledge of Java, REST APIs, and unit testing
OpenJDK: OpenJDK JDK 21.0.2 GA Release (java.net)
Maven: Maven – Installing Apache Maven

What You'll Build 🏗️¶

A Java client for the Star Wars API with the following components:

Data Transfer Objects (DTOs) to represent Star Wars characters
An interface defining the API client methods
An implementation of the interface using Java's HTTP client
Unit tests to verify the functionality

Getting Started 🚀¶

Step 1: Set Up the Project Structure¶

We'll start by setting up a basic Maven project structure. GitHub Copilot will help us create the necessary files and configurations.

Copilot Tip

If you're using an IDE like IntelliJ or VS Code, you can create a new Maven project using the built-in tools. Otherwise, you can use the Maven command-line tools to create a new project.

You can also ask Github Copilot Chat to provide you with the steps to create a Maven based Java project, with a prompt like How can I create via terminal a Java based project that already has some unit tests?

Remember hat you can directly copy commands from the chat and paste them into the terminal using the terminal icon:

If you want to use Maven command-line tools to create a new project, create an empty folder and navigate to it via terminal. Then run the following command:

mvn archetype:generate -DgroupId=com.mycompany.app -DartifactId=my-app -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

Ask Github Copilot to provide you with the command to compile the tests, by using the following sample prompt: How can I use maven to run the tests?

Your project should have the following structure:

starwarsapi/
├── pom.xml
├── src/
│   ├── main/
│   │   └── java/
│   │       └── com/
│   │           └── mycompany/
│   │               └── app/
│   │                   ├── App.java
│   │                   ├── StarWarsAPI.java
│   │                   ├── StarWarsAPIImpl.java
│   │                   └── StarWarsCharacterDTO.java
│   └── test/
│       └── java/
│           └── com/
│               └── mycompany/
│                   └── app/
│                       ├── AppTest.java
│                       └── StarWarsAPITest.java

Navigate in the folder where the project was created and run the following command:

mvn test

You should see the following output:

[INFO]
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.682 s

Step 2: Create the Maven POM File¶

Let's start by creating a pom.xml file with the necessary dependencies.

Copilot Tip

Ask GitHub Copilot to help you create a Maven POM file with dependencies for HTTP client and JSON parsing. Ask Github Copilot how you can leverage Junit 4 instead of Junit 3.

Your pom.xml should look something like below.

Sample pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mycompany.app</groupId>
<artifactId>starwarsapi</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>starwarsapi</name>
<url>http://maven.apache.org</url>
<properties>
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
    <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.13.2</version>
    <scope>test</scope>
    </dependency>
    <dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.13.0</version>
    </dependency>
</dependencies>
</project>

Refactor the Tests to Use JUnit 4¶

Ask Github Copilot to provide you with the necessary imports to use Junit 4 in your tests. Open your AppTest.java file in an editor and use Copilot Chat with an appropriate prompt to refactor the class.

Copilot Tip

Use the following prompt: I would like to refactor the tests to use Junit 4 and one basic test. The test should leverage the @Test annotation. Can you help me with the imports and the overall class structure?

Your AppTest.java file should look like the following sample solution. Be careful with the package name, it should match the one you used when creating the project.

Sample Solution

package com.mycompany.app;

import org.junit.Test;
import static org.junit.Assert.*;

/**
* Unit test for simple App.
*/
public class AppTest 
{

    @Test
    public void testApp()
    {
        assertTrue( true );
    }
}

Step 3: Create the Data Transfer Object (DTO)¶

Please navigate in your browser to the Star Wars API and get familiar with the API. We will create a DTO class to represent a Star Wars Person.

Let's start by using Luke Skywalker as an example: https://swapi.info/people/1

You can see the example payload directly at the page.

Please copy the JSON in your clipboard:

{  
    "name": "Luke Skywalker",
    "height": "172",
    "mass": "77",
    "hair_color": "blond",
    "skin_color": "fair",
    "eye_color": "blue",
    "birth_year": "19BBY",
    "gender": "male",
    "homeworld": "https://swapi.info/api/planets/1",
    "films": [
        "https://swapi.info/api/films/1",
        "https://swapi.info/api/films/2",
        "https://swapi.info/api/films/3",
        "https://swapi.info/api/films/6"
    ],
    "species": [],
    "vehicles": [
        "https://swapi.info/api/vehicles/14",
        "https://swapi.info/api/vehicles/30"
    ],
    "starships": [
        "https://swapi.info/api/starships/12",
        "https://swapi.info/api/starships/22"
    ],
    "created": "2014-12-09T13:50:51.644000Z",
    "edited": "2014-12-20T21:17:56.891000Z",
    "url": "https://swapi.info/api/people/1"
}

Now, let's create a DTO to represent a Star Wars character.

Copilot Tip

Create a new file called StarWarsCharacterDTO.java and use Github Copilot chat to create a DTO class for the Star Wars Person. You can use the JSON payload above as an example payload within the prompt.

Remember that you can directly create files out of Copilot chat by clicking on the three dots icon and then clicking Insert into New File, if you are using the Ask mode:

image: insert into new file

Sample solution

package com.mycompany.app;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;

/**
* Data Transfer Object for Star Wars character from SWAPI
*/
@JsonIgnoreProperties(ignoreUnknown = true)
public class StarWarsCharacterDTO {
    private String name;
    private String height;
    private String mass;
    @JsonProperty("hair_color")
    private String hair_color;
    @JsonProperty("skin_color")
    private String skinColor;
    @JsonProperty("eye_color")
    private String eye_color;
    @JsonProperty("birth_year")
    private String birthYear;
    private String gender;
    private String homeworld;
    private String[] films;
    private String[] species;
    private String[] vehicles;
    private String[] starships;
    private String created;
    private String edited;
    private String url;

    // Getters and setters
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getHeight() {
        return height;
    }

    public void setHeight(String height) {
        this.height = height;
    }

    public String getMass() {
        return mass;
    }

    public void setMass(String mass) {
        this.mass = mass;
    }

    public String getHair_color() {
        return hair_color;
    }

    public void setHair_color(String hair_color) {
        this.hair_color = hair_color;
    }

    public String getSkinColor() {
        return skinColor;
    }

    public void setSkinColor(String skinColor) {
        this.skinColor = skinColor;
    }

    public String getEye_color() {
        return eye_color;
    }

    public void setEye_color(String eye_color) {
        this.eye_color = eye_color;
    }

    public String getBirthYear() {
        return birthYear;
    }

    public void setBirthYear(String birthYear) {
        this.birthYear = birthYear;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getHomeworld() {
        return homeworld;
    }

    public void setHomeworld(String homeworld) {
        this.homeworld = homeworld;
    }

    public String[] getFilms() {
        return films;
    }

    public void setFilms(String[] films) {
        this.films = films;
    }

    public String[] getSpecies() {
        return species;
    }

    public void setSpecies(String[] species) {
        this.species = species;
    }

    public String[] getVehicles() {
        return vehicles;
    }

    public void setVehicles(String[] vehicles) {
        this.vehicles = vehicles;
    }

    public String[] getStarships() {
        return starships;
    }

    public void setStarships(String[] starships) {
        this.starships = starships;
    }

    public String getCreated() {
        return created;
    }

    public void setCreated(String created) {
        this.created = created;
    }

    public String getEdited() {
        return edited;
    }

    public void setEdited(String edited) {
        this.edited = edited;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }
}

Remember that this file needs to be stored in the same folder like your App.java file. The file needs to have the same filename as the class name (eg StarWarsCharacterDTO.java in this example).

Copilot Tip

If you are facing an error in the StarWarsCharacterDTO class. you can ask Github Copilot to help you fix the error.

On Mac press CMD + . and on Windows press Control + . to open the quick fix menu and use the Github Copilot to fix the error.

Quick fix menu should look like this:

quick fix menu image

Step 4: Create the API Interface¶

We will create an interface that will be used to query the Star Wars API. The interface will have a method that will return a StarWarsCharacterDTO object. As we need to have a start we will use the Luke Skywalker example and also use a method to query specificly for Luke Skywalker.

Copilot Tip

Create a new file called StarWarsAPI.java in the same folder as your App.java file. If you have problems creating this file then use the Github Copilot chat to help you create the file. We need to have a method that returns Luke Skywalker as an StarWarsCharacterDTO object.

Sample Prompt

Can you help me create a plain java interface that queries the Star Wars API and returns a StarWarsCharacterDTO object? I would like to start with just one method for querying Luke Skywalker. The interface should be called StarWarsAPI.

Don't forget the add the relevant context to the GitHub Copilot.

Your StarWarsAPI.java file should look like the sample below and been stored in the same folder like your App.java and StarWarsCharacterDTO.java file:

Sample Solution

package com.mycompany.app;

import java.io.IOException;

/**
* Interface for Star Wars API client
*/
public interface StarWarsAPI {
    /**
    * Get Luke Skywalker's information
    * @return StarWarsCharacterDTO with Luke Skywalker's data
    * @throws IOException if an I/O error occurs
    */
    StarWarsCharacterDTO getLukeSkywalker() throws IOException;

    /**
    * Get Darth Vader's information
    * @return StarWarsCharacterDTO with Darth Vader's data
    * @throws IOException if an I/O error occurs
    */
    StarWarsCharacterDTO getDarthVader() throws IOException;
}

Step 5: Generate a Test for the StarWarsAPI Interface¶

We will now create a test for the StarWarsAPI interface. The test will be used to verify that the interface is working as expected. We will use Junit 4 to create the test.

Use the Github Copilot Chat to create a test for the StarWarsAPI interface. The test should verify that the getLukeSkywalker method is working as expected. The test should be stored in the same folder like your AppTest.java file.

Copilot Tip

Use the Github Copilot popup to create the test. Leverage the /tests command to let Copilot generate the test for you. An example prompt could be: /tests Create a test that is checking if the retrieved object from the Star Wars API is fine. Accept the suggestion of Copilot and store the file next to your AppTest.java file as StarWarsAPITest.java file.

Careful: Most likely you will have to adjust the package name in the generated test file and import the IOException. You can use the quick fix menu to do so with Github Copilot.

Sample StarWarsAPITest.java file

package com.mycompany.app;

import org.junit.Test;
import static org.junit.Assert.*;

import java.io.IOException;

public class StarWarsAPITest {

    @Test
    public void testGetLukeSkywalker() {
        StarWarsAPI starWarsAPI = new StarWarsAPIImpl();
        try {
            StarWarsCharacterDTO lukeSkywalker = starWarsAPI.getLukeSkywalker();
            assertNotNull(lukeSkywalker);
        } catch (IOException e) {
            fail("IOException occurred: " + e.getMessage());
        }
    }
}

You will see that the StarWarsAPIImpl class is not yet created. And that we still have compilation errors. We will fix this in the next steps.

Step 6: Implement the API Interface¶

Now, let's implement the interface using Java's HTTP client.

We will first create the StarWarsAPIImpl class that implements the StarWarsAPI interface. The class will have a method that will return a StarWarsCharacterDTO object. As we need to have a start, we will use the Luke Skywalker example and also use a method to query specificly for Luke Skywalker.

Copilot Tip

Create a new file called StarWarsAPIImpl.java in the same folder as your App.java file. You can use VSCode to create this.

The File StarWarsAPIImpl.java will look like this:

public class StarWarsAPIImpl  {
}

Use the auto completion feature of VSCode to implement the interface. Move the cursor behind the class name and press space. You should see implements StarWarsAPI. Press tab to accept the suggestion.

The file should now look like this:

public class StarWarsAPIImpl implements StarWarsAPI {
}

Now we will implement the method. Just move the cursor on the class name and use the quick fix menu to implement the method:

use quick fix image

Your StarWarsAPIImpl.java file should look like the sample below:

Sample Solution

package com.mycompany.app;

import java.io.IOException;

public class StarWarsAPIImpl implements StarWarsAPI{

    @Override
    public StarWarsCharacterDTO getLukeSkywalker() throws IOException {
        // TODO Auto-generated method stub
        throw new UnsupportedOperationException("Unimplemented method 'getLukeSkywalker'");
    }  

}

Your error in the StarWarsAPITest.java file should be gone now. Run the tests again to make sure everything is working as expected. The tests should fail.

Implement the `getLukeSkywalker` Method with HTTP Client¶

We will now implement the getLukeSkywalker method in the StarWarsAPIImpl class. We will use the Java HttpClient to query the Star Wars API and retrieve the information about Luke Skywalker from the url: https://swapi.info/api/people/1

Copilot Tip

Click in the body of the getLukeSkywalker method and use iterative prompting to implement the method.

The method should be able fulfill the following points:

instantiate a HttpClient object
create a HttpRequest object using the GET method and the url https://swapi.info/api/people/1
send the request and retrieve the response
parse the response body to a StarWarsCharacterDTO object
return the StarWarsCharacterDTO object

Sample Prompt

You can use the following prompts one by one to implement the method. Accept the suggestions by pressing Tab:

// Use Java HttpClient to make a GET request to the Star Wars API // The URL to get Luke Skywalker is https://swapi.info/api/people/1 // Create a new instance of HttpClient
// Create a new instance of HttpRequest
// Send the request and retrieve the response
// Parse the response body to a StarWarsCharacterDTO object
// Return the StarWarsCharacterDTO object

Sample Solution

package com.mycompany.app;

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient; // Import the HttpClient class
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class StarWarsAPIImpl implements StarWarsAPI{

    @Override
    public StarWarsCharacterDTO getLukeSkywalker() throws IOException {

        // Use Java HttpClient to make a GET request to the Star Wars API
        // The URL to get Luke Skywalker is https://swapi.info/api/people/1
        // Create a new instance of HttpClient
        HttpClient client = HttpClient.newHttpClient();

        // Create a new instance of HttpRequest
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://swapi.info/api/people/1"))
            .build();

        // Send the request and get the response
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        // Parse the response JSON into a StarWarsCharacterDTO object
        ObjectMapper mapper = new ObjectMapper();
        StarWarsCharacterDTO lukeSkywalker = mapper.readValue(response.body(), StarWarsCharacterDTO.class);

        return lukeSkywalker;
    }    
}

You will see that there is an error with the ObjectMapper class. We will fix this in the next steps.

Fixing the ObjectMapper Error¶

The ObjectMapper class is not yet imported. But even then we need to add the jackson-databind dependency to the pom.xml file. Use the Github Copilot to help with this.

Copilot Tip

Use Github Copilot to generate the import in your StarWarsAPIImpl.java file to import com.fasterxml.jackson.databind.ObjectMapper;
Use Github Copilot to generate the dependency in your pom.xml file to com.fasterxml.jackson.core:jackson-databind:2.13.0

You can use Github Copilot /fix command to fix the error in the StarWarsAPIImpl.java file. You can also use the right click menu to fix the error.

You can also ask Github Copilot Chat to provide you with the necessary dependency for the pom.xml file. A prompt could be: I need to add the jackson-databind dependency to the pom.xml file. Can you help me with this?

A popup from the Java Extension Pack will appear. Accept the suggestion to rebuild the Java Class Path.

Sample Solution for StarWarsAPIImpl.java file

package com.mycompany.app;

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient; // Import the HttpClient class
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import com.fasterxml.jackson.databind.ObjectMapper;

public class StarWarsAPIImpl implements StarWarsAPI{

    @Override
    public StarWarsCharacterDTO getLukeSkywalker() throws IOException {

        // Use Java HttpClient to make a GET request to the Star Wars API
        // The URL to get Luke Skywalker is https://swapi.info/api/people/1

        // Create a new instance of HttpClient
        HttpClient client = HttpClient.newHttpClient();

        // Create a new instance of HttpRequest
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://swapi.info/api/people/1"))
            .build();

        // Send the request and get the response
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        // Parse the response JSON into a StarWarsCharacterDTO object
        ObjectMapper mapper = new ObjectMapper();
        StarWarsCharacterDTO lukeSkywalker = mapper.readValue(response.body(), StarWarsCharacterDTO.class);

        return lukeSkywalker;
    }  
}

Sample Solution for pom.xml file

<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mycompany.app</groupId>
<artifactId>my-app</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>my-app</name>
<url>http://maven.apache.org</url>
<dependencies>
    <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.13.2</version>
    <scope>test</scope>
    </dependency>
    <!-- Add this block for jackson-databind -->
    <dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.13.0</version>
    </dependency>
</dependencies>
</project>

Nevertheless there is now a new error in the StarWarsAPIImpl.java file. We will fix this in the next steps.

Fixing the InterruptedException Error¶

The getLukeSkywalker method throws an IOException. But the HttpClient class also throws an InterruptedException.

We will fix this by adding the InterruptedException to the throws clause of the method. This also means that we need to add the InterruptedException to the throws clause of the getLukeSkywalker method in the StarWarsAPI interface. And afterwards to the try/catch block in the StarWarsAPITest.java file.

Use the Quick Fix menu (CMD+. or Control+.) to add the InterruptedException to the throws clause of the getLukeSkywalker method.
Use the Quick Fix menu (CMD+. or Control+.) to add the InterruptedException to the throws clause of the getLukeSkywalker method in the StarWarsAPI interface.
Use the Quick Fix menu (CMD+. or Control+.) to add the InterruptedException to the try/catch block in the StarWarsAPITest.java file.

After these steps, your files should look like the samples below:

Sample Solution for StarWarsAPIImpl.java File

package com.mycompany.app;

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient; // Import the HttpClient class
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import com.fasterxml.jackson.databind.ObjectMapper;

public class StarWarsAPIImpl implements StarWarsAPI{

    @Override
    public StarWarsCharacterDTO getLukeSkywalker() throws IOException, InterruptedException {

        // Use Java HttpClient to make a GET request to the Star Wars API
        // The URL to get Luke Skywalker is https://swapi.info/api/people/1

        // Create a new instance of HttpClient
        HttpClient client = HttpClient.newHttpClient();

        // Create a new instance of HttpRequest
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://swapi.info/api/people/1"))
            .build();

        // Send the request and get the response
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        // Parse the response JSON into a StarWarsCharacterDTO object
        ObjectMapper mapper = new ObjectMapper();
        StarWarsCharacterDTO lukeSkywalker = mapper.readValue(response.body(), StarWarsCharacterDTO.class);

        return lukeSkywalker;
    }  
}

Sample Solution for StarWarsAPI.java File

package com.mycompany.app;

import java.io.IOException;

public interface StarWarsAPI {

    StarWarsCharacterDTO getLukeSkywalker() throws IOException, InterruptedException;

}

Sample Solution for StarWarsAPITest.java File

package com.mycompany.app;

import org.junit.Test;
import static org.junit.Assert.*;

import java.io.IOException;

public class StarWarsAPITest {

    @Test
    public void testGetLukeSkywalker() {

        StarWarsAPI starWarsAPI = new StarWarsAPIImpl();
        try {
            StarWarsCharacterDTO lukeSkywalker = starWarsAPI.getLukeSkywalker();
            assertNotNull(lukeSkywalker);
        } catch (IOException | InterruptedException e) {
            fail("IOException occurred: " + e.getMessage());
        }
    }
}

Run the tests¶

Run the tests again to make sure everything is working as expected. The tests might fail with the following:

[ERROR] Failures: 
[ERROR]    StarWarsAPITest.testGetLukeSkywalker:20 IOException occurred: No content to map due to end-of-input
 at [Source: (String)""; line: 1, column: 0]

Copilot Tip

Ask Github Copilot to provide you with the necessary code to fix the error. The hint might be not enough.
Go in your browser. Open the network tab in the developer tools. And visit the url https://swapi.info/api/people/1. Look at the network and use this info to fix the error.

To solve the issue, open the StarWarsAPIImpl.java file. Go in Github Copilot Chat and ask for help to fix the error with the following sample prompt: When visiting the url https://swapi.info/api/people/1 I see in my network tab of the dev consoles in my browser a 308. Does this lead to an error in my test?

Then, replace the instance of the HttpClient with the following code: HttpClient client = HttpClient.newBuilder().followRedirects(HttpClient.Redirect.ALWAYS).build();

After that, rerun the tests to make sure everything is working as expected: mvn test

You can find the sample solution of the StarWarsAPIImpl.java file below.

Sample Solution

package com.mycompany.app;

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient; // Import the HttpClient class
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import com.fasterxml.jackson.databind.ObjectMapper;

public class StarWarsAPIImpl implements StarWarsAPI{

    @Override
    public StarWarsCharacterDTO getLukeSkywalker() throws IOException, InterruptedException {

        // Use Java HttpClient to make a GET request to the Star Wars API
        // The URL to get Luke Skywalker is https://swapi.info/api/people/1

        // Create a new instance of HttpClient
        HttpClient client = HttpClient.newBuilder()
            .followRedirects(HttpClient.Redirect.ALWAYS)
            .build();

        // Create a new instance of HttpRequest
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://swapi.info/api/people/1"))
            .build();

        // Send the request and get the response
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        // Parse the response JSON into a StarWarsCharacterDTO object
        ObjectMapper mapper = new ObjectMapper();
        StarWarsCharacterDTO lukeSkywalker = mapper.readValue(response.body(), StarWarsCharacterDTO.class);

        return lukeSkywalker;
    }  
}

Adding more Asserts to the Test¶

We need to add a little more asserts to the test to check if the information about Luke Skywalker is correct. We will check if the name of Luke Skywalker is correct and if the height is correct.

Open the StarWarsAPITest.java file.
Use comments as prompts after the assertNotNull line to ask Github Copilot to provide you with the necessary code to check if the name of Luke Skywalker is correct and if the height is correct.

Copilot Tip

Use the following prompts as comments to ask Github Copilot to provide you with the necessary code. Press enter after the comment and Tab to accept the suggestion.

// Check if the name of Luke Skywalker is correct
// Check if the name of Luke Skywalker is correct

Your StarWarsAPITest.java file should look like the sample below.

Sample Solution

package com.mycompany.app;

import org.junit.Test;
import static org.junit.Assert.*;

import java.io.IOException;

public class StarWarsAPITest {

    @Test
    public void testGetLukeSkywalker() {

        StarWarsAPI starWarsAPI = new StarWarsAPIImpl();
        try {
            StarWarsCharacterDTO lukeSkywalker = starWarsAPI.getLukeSkywalker();
            assertNotNull(lukeSkywalker);

            // Check if the name of Like Skywalker is correct
            assertEquals("Luke Skywalker", lukeSkywalker.getName());

            // Check if the height of Luke Skywalker is correct
            assertEquals("172", lukeSkywalker.getHeight());

        } catch (IOException | InterruptedException e) {
            fail("IOException occurred: " + e.getMessage());
        }
    }
}

Optional: Add Additional Characters to the StarWarsAPI Interface¶

Now that we have implemented the getLukeSkywalker method we will add additional methods to the StarWarsAPI interface to query other Star Wars characters. We will now query for our beloved Darth Vader.

Add a new method to the StarWarsAPI interface that will return a StarWarsCharacterDTO object for Darth Vader.

Copilot Tip

You can use the following prompt as a comment to ask Github Copilot to provide you with the necessary code. Press enter after the comment and Tab to accept the suggestion: // Get Darth Vader

Your StarWarsAPI.java file should look like the sample below.

Sample Solution

package com.mycompany.app;

import java.io.IOException;

public interface StarWarsAPI {

    StarWarsCharacterDTO getLukeSkywalker() throws IOException, InterruptedException;
    // Get Darth Vader
    StarWarsCharacterDTO getDarthVader() throws IOException, InterruptedException;
}

This will lead to a compile error in the StarWarsAPIImpl class. We will fix this in the next steps.

Implement the getDarthVader method in the StarWarsAPIImpl class¶

We will now implement the getDarthVader method in the StarWarsAPIImpl class. We will use the Java HttpClient to query the Star Wars API and retrieve the information about Darth Vader from the url: https://swapi.info/api/people/4

Navigate to the StarWarsAPIImpl.java file. Use a comment as a prompt after the getLukeSkywalker method to ask Github Copilot to provide you with the necessary code to implement the getDarthVader method.

Copilot Tip

Use the following prompt as a comment to ask Github Copilot to provide you with the necessary code. Press enter after the comment and Tab to accept the suggestion: // Implement the getDarthVader method

Your StarWarsAPIImpl.java file should look like the sample below.

Sample Solution

package com.mycompany.app;

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient; // Import the HttpClient class
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import com.fasterxml.jackson.databind.ObjectMapper;

public class StarWarsAPIImpl implements StarWarsAPI{

    @Override
    public StarWarsCharacterDTO getLukeSkywalker() throws IOException, InterruptedException {

        // Use Java HttpClient to make a GET request to the Star Wars API
        // The URL to get Luke Skywalker is https://swapi.info/api/people/1

        // Create a new instance of HttpClient
        HttpClient client = HttpClient.newBuilder()
            .followRedirects(HttpClient.Redirect.ALWAYS)
            .build();

        // Create a new instance of HttpRequest
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://swapi.info/api/people/1"))
            .build();

        // Send the request and get the response
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        // Parse the response JSON into a StarWarsCharacterDTO object
        ObjectMapper mapper = new ObjectMapper();
        StarWarsCharacterDTO lukeSkywalker = mapper.readValue(response.body(), StarWarsCharacterDTO.class);

        return lukeSkywalker;


    }

    // Implement the getDarthVader method
    @Override
    public StarWarsCharacterDTO getDarthVader() throws IOException, InterruptedException {

        // Use Java HttpClient to make a GET request to the Star Wars API
        // The URL to get Darth Vader is https://swapi.info/api/people/4

        // Create a new instance of HttpClient
        HttpClient client = HttpClient.newBuilder()
            .followRedirects(HttpClient.Redirect.ALWAYS)
            .build();

        // Create a new instance of HttpRequest
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://swapi.info/api/people/4"))
            .build();

        // Send the request and get the response
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        // Parse the response JSON into a StarWarsCharacterDTO object
        ObjectMapper mapper = new ObjectMapper();
        StarWarsCharacterDTO darthVader = mapper.readValue(response.body(), StarWarsCharacterDTO.class);

        return darthVader;      

    }  
}

Rerun the tests to see if it is still working. Next we will add a test for the getDarthVader method.

Add a test for the getDarthVader method¶

We will now add a test for the getDarthVader method in the StarWarsAPITest class. The test will be used to verify that the getDarthVader method is working as expected.

Add a new test method to the StarWarsAPITest class that will test the getDarthVader method. You can use a comment as a prompt to do so.

Copilot Tip

Open the StarWarsAPITest.java file. Use a comment as a prompt after the testGetLukeSkywalker method to ask Github Copilot to provide you with the necessary code to implement the testGetDarthVader method: // Test the getDarthVader method

After that, rerun the tests to make sure everything is working as expected: mvn test

Your StarWarsAPITest.java file should look like the sample below.

Sample Solution

package com.mycompany.app;

import org.junit.Test;
import static org.junit.Assert.*;

import java.io.IOException;

public class StarWarsAPITest {

    @Test
    public void testGetLukeSkywalker() {

        StarWarsAPI starWarsAPI = new StarWarsAPIImpl();
        try {
            StarWarsCharacterDTO lukeSkywalker = starWarsAPI.getLukeSkywalker();
            assertNotNull(lukeSkywalker);

            // Check if the name of Like Skywalker is correct
            assertEquals("Luke Skywalker", lukeSkywalker.getName());

            // Check if the height of Luke Skywalker is correct
            assertEquals("172", lukeSkywalker.getHeight());

        } catch (IOException | InterruptedException e) {
            fail("IOException occurred: " + e.getMessage());
        }
    }

    // Test the getDarthVader method
    @Test
    public void testGetDarthVader() {

        StarWarsAPI starWarsAPI = new StarWarsAPIImpl();
        try {
            StarWarsCharacterDTO darthVader = starWarsAPI.getDarthVader();
            assertNotNull(darthVader);

            // Check if the name of Darth Vader is correct
            assertEquals("Darth Vader", darthVader.getName());

            // Check if the height of Darth Vader is correct
            assertEquals("202", darthVader.getHeight());

        } catch (IOException | InterruptedException e) {
            fail("IOException occurred: " + e.getMessage());
        }
    }
}

Step 7: Refactor the API Implementation¶

There's a lot of duplicated code in the getLukeSkywalker and getDarthVader methods. Let's refactor the code to extract the common code into a new private method.

Use the Github Copilot chat to help you refactor the getLukeSkywalker and getDarthVader methods in the StarWarsAPIImpl class. The common code should be extracted into a new private method called getStarWarsCharacter. The method should only receive an id as a parameter and return a StarWarsCharacterDTO object.

Copilot Tip

Open your StarWarsAPIImpl.java file.
Use Github Copilot chat to help you refactor the getLukeSkywalker and getDarthVader methods. Use the following prompt: Can you help me refactoring this class to use a private method getStarWarsCharacter to retrieve the payloads and avoid duplicated code in the different methods. I want to provide an Id to the private method. I need the whole refactored class as a result including the getLukeSkywalker and getDarthVaeder methods.
Be careful: The retrieved class is missing the package declaration. Add the package declaration to the class

After refactoring, your StarWarsAPIImpl.java file should look like the sample below.

Sample Solution

package com.mycompany.app;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.io.IOException;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
* Implementation of the Star Wars API client
*/
public class StarWarsAPIImpl implements StarWarsAPI {
    private HttpClient client;

    public StarWarsAPIImpl() {
        this.client = HttpClient.newBuilder()
            .followRedirects(HttpClient.Redirect.ALWAYS)
            .build();
    }

    @Override
    public StarWarsCharacterDTO getLukeSkywalker() throws IOException, InterruptedException {
        return getStarWarsCharacter(1);
    }

    @Override
    public StarWarsCharacterDTO getDarthVader() throws IOException, InterruptedException {
        return getStarWarsCharacter(4);
    }

    private StarWarsCharacterDTO getStarWarsCharacter(int id) throws IOException, InterruptedException {
        String url = "https://swapi.dev/api/people/" + id + "/";
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create(url))
            .build();

        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

        ObjectMapper mapper = new ObjectMapper();
        return mapper.readValue(response.body(), StarWarsCharacterDTO.class);
    }
}

Rerun the tests to make sure everything is working as expected. The tests should pass.

Step 8: Create a Simple App Class¶

Let's create a simple application class to demonstrate the API client.

Copilot Tip

Create a new file called App.java and add a comment describing what you want to create.

Sample App.java

package com.mycompany.app;

import java.io.IOException;

/**
* Main application class
*/
public class App {
    public static void main(String[] args) {
        System.out.println("Star Wars API Client");

        StarWarsAPI api = new StarWarsAPIImpl();

        try {
            System.out.println("Getting Luke Skywalker's information...");
            StarWarsCharacterDTO luke = api.getLukeSkywalker();
            System.out.println("Name: " + luke.getName());
            System.out.println("Height: " + luke.getHeight() + " cm");
            System.out.println("Mass: " + luke.getMass() + " kg");
            System.out.println("Hair color: " + luke.getHair_color());
            System.out.println("Eye color: " + luke.getEye_color());

            System.out.println("\nGetting Darth Vader's information...");
            StarWarsCharacterDTO vader = api.getDarthVader();
            System.out.println("Name: " + vader.getName());
            System.out.println("Height: " + vader.getHeight() + " cm");
            System.out.println("Mass: " + vader.getMass() + " kg");
            System.out.println("Hair color: " + vader.getHair_color());
            System.out.println("Eye color: " + vader.getEye_color());
        } catch (IOException | InterruptedException e) {
            System.err.println("Error: " + e.getMessage());
            e.printStackTrace();
        }
    }
}

Step 9: Run the Tests¶

Run the tests to make sure everything is working as expected.

Copilot Tip

Use the Maven command mvn test to run the tests.

If everything is set up correctly, the tests should pass, indicating that your Star Wars API client is working properly.

Bonus Challenges 🌟¶

If you have extra time, try these bonus challenges with GitHub Copilot:

Add a method to get information about a character by name (hint: you'll need to use the search endpoint)
Add a method to get information about a planet
Add a method to get all characters from a specific film
Implement caching to avoid making the same API calls repeatedly

Summary 📝¶

In this lab, you've learned how to:

Use GitHub Copilot to create a Java client for a REST API
Create DTOs, interfaces, and implementations
Write unit tests to verify functionality
Refactor code to eliminate duplication

GitHub Copilot has helped you write code faster and with less effort, allowing you to focus on the design and architecture rather than the implementation details. This is a great example of how AI-assisted coding can enhance your development workflow, especially when working with external APIs! 🚀

Contributed by: Jeffrey Groneberg

Star Wars API Client Lab 🚀¶

Lab Overview 📋¶

What You'll Build 🏗️¶

Getting Started 🚀¶

Step 1: Set Up the Project Structure¶

Step 2: Create the Maven POM File¶

Refactor the Tests to Use JUnit 4¶

Step 3: Create the Data Transfer Object (DTO)¶

Step 4: Create the API Interface¶

Step 5: Generate a Test for the StarWarsAPI Interface¶

Step 6: Implement the API Interface¶

Implement the getLukeSkywalker Method with HTTP Client¶

Fixing the ObjectMapper Error¶

Fixing the InterruptedException Error¶

Run the tests¶

Adding more Asserts to the Test¶

Optional: Add Additional Characters to the StarWarsAPI Interface¶

Implement the getDarthVader method in the StarWarsAPIImpl class¶

Add a test for the getDarthVader method¶

Step 7: Refactor the API Implementation¶

Step 8: Create a Simple App Class¶

Step 9: Run the Tests¶

Bonus Challenges 🌟¶

Summary 📝¶

Implement the `getLukeSkywalker` Method with HTTP Client¶