Service Design Pattern

HomeServlet.java

package com.moommimit.moommim.controller;

import com.moommimit.moommim.service.NewsService;
import com.moommimit.moommim.utils.ResultCallback;
import java.io.IOException;
import java.util.logging.Logger;
import javax.inject.Inject;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(name = "HomeServlet", urlPatterns = {"/cat/*"})
public class HomeServlet extends HttpServlet {

    private static final Logger LOGGER = Logger.getLogger(HomeServlet.class.getSimpleName());

    @Inject
    private NewsService newsService;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("Home Serv");
        String name = request.getParameter("name");
        newsService.getNews(name, new ResultCallback<String[]>() {
            @Override
            public void onSuccess(String[] news) {
                for (String item : news) {
                    System.out.println("News: " + item);
                }
            }

            @Override
            public void onError(Exception ex) {
                System.out.println("Is have Error");
            }
        });
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

    }

}

NewsService.java

package com.moommimit.moommim.service;

import com.moommimit.moommim.utils.ResultCallback;

public interface NewsService {
    
    void getNews(String name, ResultCallback newsCallback);
    
}

NewsServiceImpl.java

package com.moommimit.moommim.service;

import com.moommimit.moommim.utils.ResultCallback;
import javax.enterprise.context.ApplicationScoped;

@ApplicationScoped
public class NewsServiceImpl implements NewsService {

    @Override
    public void getNews(String name, ResultCallback newsCallback) {
        boolean isHaveNews = true;
        System.out.println("Hello " + name);
        if (isHaveNews) {
            String[] news = {"Tech", "Drama", "Movie"};
            newsCallback.onSuccess(news);
        } else {
            newsCallback.onError(null);
        }
    }

}

ResultCallback.java

package com.moommimit.moommim.utils;

public interface ResultCallback<T> {

    void onSuccess(T result);

    void onError(Exception ex);

}