Lesson 1. Writing your first "echo" bot

Hello! If you want to know, how to code Telegram Bots on Java, you are on the right way!

Prepare to launch

Bot API is based on HTTP-requests, but in this book I will use Rubenlagus' library for Java.

Install the library

You can install TelegramBots library with different methods:

• Using Maven:

<dependency>
        <groupId>org.telegram</groupId>
        <artifactId>telegrambots</artifactId>
        <version>Latest</version>
</dependency>

• Using Jitpack
• Or just download .jar file with dependencies from here

In this tutorial I will use next machines:

• Ubuntu 16.04 Server with 1GB of RAM
• My home Windows 10 laptop with IntelliJ Idea pre-installed

Lets go to code!

Well, enough for words. Let's get down to buisness. In this lesson we will write simple bot that echoes everything we sent to him. Now, open IntelliJ Idea and create a new project. You can call it whatever you want. Then, dont forget to install TelegramBots library with preffered method. I think, that it is most easy to just download .jar from here

Now, when you are in the project, create files MyAmazingBot.java and Main.java within the src directory. Open MyAmazingBot.java and lets write our actual bot:

Remember! The class must extends TelegramLongPollingBot and implement necessary methods

import org.telegram.telegrambots.api.methods.send.SendMessage;
import org.telegram.telegrambots.api.objects.Update;
import org.telegram.telegrambots.bots.TelegramLongPollingBot;
import org.telegram.telegrambots.exceptions.TelegramApiException;

public class MyAmazingBot extends TelegramLongPollingBot {
    @Override
    public void onUpdateReceived(Update update) {
        // TODO
    }

    @Override
    public String getBotUsername() {
        // TODO
        return null;
    }

    @Override
    public String getBotToken() {
        // TODO
        return null;
    }
}

As you can understand, getBotUsername() and getBotToken() must return bot's username and bot's token, obtained from @BotFather. So now, our MyAmazingBot.java file will look like this:

import org.telegram.telegrambots.api.methods.send.SendMessage;
import org.telegram.telegrambots.api.objects.Update;
import org.telegram.telegrambots.bots.TelegramLongPollingBot;
import org.telegram.telegrambots.exceptions.TelegramApiException;

public class MyAmazingBot extends TelegramLongPollingBot {
    @Override
    public void onUpdateReceived(Update update) {
        // TODO
    }

    @Override
    public String getBotUsername() {
        // Return bot username
        // If bot username is @MyAmazingBot, it must return 'MyAmazingBot'
        return "MyAmazingBot";
    }

    @Override
    public String getBotToken() {
        // Return bot token from BotFather
        return "12345:qwertyuiopASDGFHKMK";
    }
}

Now, let's move on to the logic of our bot. As I said before, we want him to reply every text we send to him. onUpdateReceived(Update update) method is for us. When an update recieved, it will call this method.

@Override
public void onUpdateReceived(Update update) {

    // We check if the update has a message and the message has text
    if (update.hasMessage() && update.getMessage().hasText()) {
        // Set variables
        String message_text = update.getMessage().getText();
        long chat_id = update.getMessage().getChatId();

        SendMessage message = new SendMessage() // Create a message object object
                .setChatId(chat_id)
                .setText(message_text);
        try {
            execute(message); // Sending our message object to user
        } catch (TelegramApiException e) {
            e.printStackTrace();
        }
    }
}

Good! But how do I run the bot? Well, its a good question. Lets save that file and open Main.java. This file will instantiate TelegramBotsApi and register our new bot. It will look like this:

import org.telegram.telegrambots.ApiContextInitializer;
import org.telegram.telegrambots.TelegramBotsApi;
import org.telegram.telegrambots.exceptions.TelegramApiException;
public class Main {
    public static void main(String[] args) {

        // TODO Initialize Api Context

        // TODO Instantiate Telegram Bots API

        // TODO Register our bot
    }
}

Now, lets initialize Api Context

import org.telegram.telegrambots.ApiContextInitializer;
import org.telegram.telegrambots.TelegramBotsApi;
import org.telegram.telegrambots.exceptions.TelegramApiException;
public class Main {
    public static void main(String[] args) {
        // Initialize Api Context
        ApiContextInitializer.init();

        // TODO Instantiate Telegram Bots API

        // TODO Register our bot
    }
}

Instantiate Telegram Bots API:

import org.telegram.telegrambots.ApiContextInitializer;
import org.telegram.telegrambots.TelegramBotsApi;
import org.telegram.telegrambots.exceptions.TelegramApiException;
public class Main {
    public static void main(String[] args) {
        // Initialize Api Context
        ApiContextInitializer.init();
        // Instantiate Telegram Bots API
        TelegramBotsApi botsApi = new TelegramBotsApi();

        // TODO Register our bot
    }
}

And register our bot:

import org.telegram.telegrambots.ApiContextInitializer;
import org.telegram.telegrambots.TelegramBotsApi;
import org.telegram.telegrambots.exceptions.TelegramApiException;
public class Main {
    public static void main(String[] args) {
        // Initialize Api Context
        ApiContextInitializer.init();

        // Instantiate Telegram Bots API
        TelegramBotsApi botsApi = new TelegramBotsApi();

        // Register our bot
        try {
            botsApi.registerBot(new MyAmazingBot());
        } catch (TelegramApiException e) {
            e.printStackTrace();
        }
    }
}

Here is all our files:

src/Main.java

  import org.telegram.telegrambots.ApiContextInitializer;
  import org.telegram.telegrambots.TelegramBotsApi;
  import org.telegram.telegrambots.exceptions.TelegramApiException;
  public class Main {
    public static void main(String[] args) {
        // Initialize Api Context
        ApiContextInitializer.init();

        // Instantiate Telegram Bots API
        TelegramBotsApi botsApi = new TelegramBotsApi();

        // Register our bot
        try {
            botsApi.registerBot(new MyAmazingBot());
        } catch (TelegramApiException e) {
            e.printStackTrace();
        }
    }
}

src/MyAmazingBot.java

 import org.telegram.telegrambots.api.methods.send.SendMessage;
 import org.telegram.telegrambots.api.objects.Update;
 import org.telegram.telegrambots.bots.TelegramLongPollingBot;
 import org.telegram.telegrambots.exceptions.TelegramApiException;

 public class MyAmazingBot extends TelegramLongPollingBot {
    @Override
    public void onUpdateReceived(Update update) {

        // We check if the update has a message and the message has text
        if (update.hasMessage() && update.getMessage().hasText()) {
            // Set variables
            String message_text = update.getMessage().getText();
            long chat_id = update.getMessage().getChatId();

            SendMessage message = new SendMessage() // Create a message object object
                .setChatId(chat_id)
                .setText(message_text);
            try {
                execute(message); // Sending our message object to user
            } catch (TelegramApiException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public String getBotUsername() {
        // Return bot username
        // If bot username is @MyAmazingBot, it must return 'MyAmazingBot'
        return "MyAmazingBot";
    }

    @Override
    public String getBotToken() {
        // Return bot token from BotFather
        return "12345:qwertyuiopASDGFHKMK";
    }
}

Well done! Now we can pack our project into runnable .jar file and run it on our computer/server!

You can find all sources to this lesson in GitHub repository.

java -jar MyAmazingBot.jar

Now we can see our bot running:

Well, thats all for now. Hope to see you soon!:)