JSON marshalling

When exercising the app, you interacted with JSON payloads. How does the example app convert data between JSON format and data that can be used by Java classes? Fur this purposes akka.http has akka.http.javadsl.marshallers.jackson.Jackson

We’re using the Jackson library here, along with akka-http wrapper that provides marshallers Jackson.marshaller(). It does ot provide type safety like Spray on compile time but it still allows to to marshall data to JSON and back.

In majority of cases you’ll just need to add marshaller to complete call like following complete(StatusCodes.OK, performed, Jackson.marshaller() to be able to product JSON response. To fill object with JSON data we you’ll need to create unmarshaller with class as attribute Jackson.unmarshaller(User.class)

Data transfer classes that we are using to interact with actors does not have any links to Jackson itself:

public static class User {
  private final String name;
  private final int age;
  private final String countryOfResidence;

  public User() {
    this.name = "";
    this.countryOfResidence = "";
    this.age = 1;

  public User(String name, int age, String countryOfResidence) {
    this.name = name;
    this.age = age;
    this.countryOfResidence = countryOfResidence;

  public String getName() {
    return name;

  public int getAge() {
    return age;

  public String getCountryOfResidence() {
    return countryOfResidence;

public static class Users{
  private final List<User> users;

  public Users() {
    this.users = new ArrayList<>();

  public Users(List<User> users) {
    this.users = users;

  public List<User> getUsers() {
    return users;

While we used Jackson JSON in this example, various other libraries can be used Each library comes with different trade-offs in performance and user-friendlieness. Still Jakson is the default Java marshaller

Now that we’ve examined the example app thoroughly, let’s test a few remaining use cases.