JavaHTTPServer.java

import com.mongodb.MongoClient;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;
import org.json.JSONArray;
import org.json.JSONObject;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;

public class JavaHTTPServer {

    private static final int PORT = 8081;
    private static final int NUM_THREADS = 10;

    private ThreadPoolExecutor threadPoolExecutor;
    private MongoDatabase database;

    public JavaHTTPServer() {
        threadPoolExecutor = (ThreadPoolExecutor) Executors.newFixedThreadPool(NUM_THREADS);
        MongoClient client = null;
        try {
            client = new MongoClient("localhost", 27017);
            database = client.getDatabase("mydb");

            ServerSocket serverConnect = new ServerSocket(PORT);
            System.out.println("Server started.\nListening for connections on port : " + PORT + " ...\n");

            while (true) threadPoolExecutor.execute(new Worker(serverConnect.accept()));
        } catch (IOException e) {
            System.err.println("Server Connection error : " + e.getMessage());
        } finally {
            if (client != null) client.close();
        }
    }

    class Worker implements Runnable {

        Socket socket;

        public Worker(Socket socket) {
            this.socket = socket;
        }

        @Override
        public void run() {
            BufferedReader in = null;
            PrintWriter out = null;
            BufferedOutputStream dataOut = null;

            try {
                in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                out = new PrintWriter(socket.getOutputStream());
                dataOut = new BufferedOutputStream(socket.getOutputStream());

                String input = in.readLine();
                if(input == null) return;
                String[] parts = input.split(" ");
                String method = parts[0];
                String path = parts[1];

                System.out.println("method is " + method);
                System.out.println("path is " + path);

                if (method.equals("GET") && path.equals("/user/")) {
                    MongoCollection users = database.getCollection("users");
                    MongoCursor cursor = users.find().iterator();

                    JSONArray list = new JSONArray();
                    while (cursor.hasNext()) {
                        Document document = (Document) cursor.next();
                        JSONObject user = new JSONObject();
                        user.put("id", document.getObjectId("_id"));
                        user.put("name", document.getString("name"));
                        user.put("coins", document.getInteger("coins"));
                        JSONArray emojis = new JSONArray();
                        for (int emoji : document.getList("emojis", Integer.class)) {
                            emojis.put(emoji);
                        }
                        user.put("emojis", emojis);
                        user.put("createdAt", document.getDate("createdAt").getTime());
                        list.put(user);
                    }
                    String res = list.toString();

                    out.println("HTTP/1.1 200 OK");
                    out.println("Server: Java HTTP Server");
                    out.println("Date: " + new Date());
                    out.println("Content-type: " + "application/json");
                    out.println("Content-length: " + res.length());
                    out.println();
                    out.flush();

                    dataOut.write(res.getBytes(), 0, res.length());
                    dataOut.flush();
                }

            } catch (Exception ioe) {
                ioe.printStackTrace();
                System.err.println("Server error : " + ioe);
            } finally {
                try {
                    in.close();
                    out.close();
                    dataOut.close();
                    socket.close(); // we close socket connection
                } catch (Exception e) {
                    System.err.println("Error closing stream : " + e.getMessage());
                }
            }
        }
    }
}