Creating a simple mock json service with laggom

Question

Lagom seems to be interesting but I'm having hard time to make something simple. It seems that I haven't understood how it works and the hello world example, although it works, I don't understand how to use it.

I'm trying to create a simple restful service that takes at its header two parameters and produces a json object. For instance in the MyService.java I have:

public interface BookService extends Service {

    ServiceCall<NotUsed, String> getAllBook();

    /**
     * @return
     */
    @Override
    default Descriptor descriptor() {

        return named("book").withCalls(
            restCall(GET, "/api/get-all-book", this::getAllBook)
        ).withAutoAcl(true);
    }
}

Then in BookServiceImpl I have:

public class BookServiceImpl implements BookService {

    private final PersistentEntityRegistry persistentEntityRegistry;

    /**
     * @param registry
     * @param readSide
     * @param session
     */
    @Inject
    public BookServiceImpl(final PersistentEntityRegistry registry, ReadSide readSide, CassandraSession session) {
        this.persistentEntityRegistry = registry;

        persistentEntityRegistry.register(BookEntity.class);
        readSide.register(BookEventProcessor.class);
    }


    @Override
    public ServiceCall<NotUsed, String> getAllBook() {
        return request -> {

            JSONObject myBook= new JSONObject();
            myBook.put("name","BookName");
            myBook.put("description","A description");
            myBook.put("price","$16");
            myBook.put("status","available");

            //how do I return JSONBject.toString()
        };
    }
}

And then how do I put headers parameters? Some documentation that explains basics would be very helpful.

Thanks in advance

Answer 1

You need to create a POJO class that actually does the JSON. By using the lombok package in service implementation:

package mybook;


import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Value;

import javax.annotation.concurrent.Immutable;

@Value
@Builder
@Immutable
@JsonDeserialize
@AllArgsConstructor
public class Book {
    String name; 
    String description; 
    String value; 
    String status;
}

Then in service:

public interface BookService extends Service {

    ServiceCall<NotUsed, Book> getAllBook();

    /**
     * @return
     */
    @Override
    default Descriptor descriptor() {

        return named("book").withCalls(
            restCall(GET, "/api/get-all-book", this::getAllBook)
        ).withAutoAcl(true);
    }
}

And then in implementation:

public class BookServiceImpl implements BookService {

    @Override
    public ServiceCall<NotUsed, Book> getAllBook() {
        return request -> {
            Book myBook =     Book.builder().
                                name("BookName").
                                description("A description").
                                price("16€").
                                status("available").build();

            return completedFuture(myBook);
        };
    }
}