WebSockets & Real-Time Systems with Spring · Lekcja

Implementowanie publicznych pokojów czatu

Proszę opracować funkcjonalność umożliwiającą użytkownikom dołączanie do publicznych pokojów czatu i uczestniczenie w rozmowach w formie transmisji.

Implementowanie publicznych pokojów czatu to bezpłatna lekcja WebSockets & Real-Time Systems with Spring na CoddyKit. To lekcja 2 z 4. Możesz przeczytać całą lekcję poniżej za darmo — a potem ćwiczyć ją interaktywnie w przeglądarce z wbudowanym edytorem kodu i tutorem AI dostępnym 24/7. To część ścieżki edukacyjnej WebSockets & Real-Time Systems with Spring, a Twój postęp synchronizuje się między webem a aplikacją CoddyKit. Kurs WebSockets & Real-Time Systems with Spring zawiera 4 lekcji w sumie.

Części tej lekcji nie zostały jeszcze przetłumaczone i są wyświetlane po angielsku.

Public Chat Rooms Explained

Welcome! In this lesson, we'll build public chat rooms. These are common spaces where many users can send and receive messages, visible to everyone in that room.

Think of a general discussion channel in a messaging app. The key characteristic here is broadcast communication: one message sent by any user is instantly relayed to all other users currently in the room.

STOMP Topics for Rooms

In Spring with STOMP, we use topics to represent chat rooms. A topic is like a channel clients can subscribe to. Messages sent to a topic are broadcast to all its subscribers.

For public rooms, we often use a common topic path like /topic/public-chat.
Clients subscribe to this topic to receive messages.
Clients send messages to a specific application destination, which the server then forwards to the topic.

Simple Chat Message Model

Before implementing the chat logic, we need a simple structure for our messages. This helps ensure everyone understands the data being sent.

A basic ChatMessage might include the message type (e.g., CHAT, JOIN, LEAVE), the sender's name, and the actual content. Here's a quick look:

public class ChatMessage {
    public enum MessageType {
        CHAT,
        JOIN,
        LEAVE
    }
    private MessageType type;
    private String content;
    private String sender;

    public ChatMessage() {}
    public MessageType getType() { return type; }
    public void setType(MessageType type) { this.type = type; }
    public String getContent() { return content; }
    public void setContent(String content) { this.content = content; }
    public String getSender() { return sender; }
    public void setSender(String sender) { this.sender = sender; }

    @Override
    public String toString() {
        return "ChatMessage{" + "type=" + type + ", sender='" + sender + "', content='" + content + "'}";
    }
}

Server-Side Chat Controller

To handle incoming chat messages and broadcast them, we'll create a Spring @Controller. This controller will listen for messages sent to a specific application destination (e.g., /app/chat.sendMessage) and then use a SimpMessageSendingOperations (often SimpMessagingTemplate) to broadcast them to our public topic (/topic/public-chat).

Try running this example:

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.messaging.handler.annotation.Payload;
import org.springframework.messaging.simp.SimpMessageSendingOperations;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.stereotype.Controller;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;

// ChatMessage POJO (for simplicity, included here)
class ChatMessage {
    public enum MessageType { CHAT, JOIN, LEAVE }
    private MessageType type;
    private String content;
    private String sender;
    public ChatMessage() {}
    public MessageType getType() { return type; }
    public void setType(MessageType type) { this.type = type; }
    public String getContent() { return content; }
    public void setContent(String content) { this.content = content; }
    public String getSender() { return sender; }
    public void setSender(String sender) { this.sender = sender; }
    @Override
    public String toString() {
        return "ChatMessage{" + "type=" + type + ", sender='" + sender + "', content='" + content + "'}";
    }
}

// WebSocket Configuration
@Configuration
@EnableWebSocketMessageBroker
class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
    @Override
    public void configureMessageBroker(MessageBrokerRegistry config) {
        config.enableSimpleBroker("/topic");
        config.setApplicationDestinationPrefixes("/app");
    }
    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/ws").withSockJS();
    }
}

// Chat Controller
@Controller
class ChatController {
    private final SimpMessageSendingOperations messagingTemplate;

    public ChatController(SimpMessageSendingOperations messagingTemplate) {
        this.messagingTemplate = messagingTemplate;
    }

    @MessageMapping("/chat.sendMessage")
    public void sendMessage(@Payload ChatMessage chatMessage) {
        System.out.println("Received CHAT message from " + chatMessage.getSender() + ": " + chatMessage.getContent());
        messagingTemplate.convertAndSend("/topic/public-chat", chatMessage);
    }
}

// Main Application
@SpringBootApplication
public class Main {
    public static void main(String[] args) {
        SpringApplication.run(Main.class, args);
        System.out.println("\n--- Spring Boot Chat Server Started ---");
        System.out.println("Connect to ws://localhost:8080/ws");
        System.out.println("Send CHAT messages to /app/chat.sendMessage and subscribe to /topic/public-chat");
    }
}

Broadcasting User Joins

When a user first connects or explicitly "joins" a chat room, it's good practice to notify everyone else. We can do this by sending a special JOIN type message.

Our @MessageMapping can detect these join events and broadcast them to the same public topic. This way, all clients know who has entered the room.

Let's extend our ChatController to handle JOIN messages:

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.messaging.handler.annotation.Payload;
import org.springframework.messaging.simp.SimpMessageSendingOperations;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.stereotype.Controller;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;

class ChatMessage {
    public enum MessageType { CHAT, JOIN, LEAVE }
    private MessageType type;
    private String content;
    private String sender;
    public ChatMessage() {}
    public MessageType getType() { return type; }
    public void setType(MessageType type) { this.type = type; }
    public String getContent() { return content; }
    public void setContent(String content) { this.content = content; }
    public String getSender() { return sender; }
    public void setSender(String sender) { this.sender = sender; }
    @Override
    public String toString() {
        return "ChatMessage{" + "type=" + type + ", sender='" + sender + "', content='" + content + "'}";
    }
}

@Configuration
@EnableWebSocketMessageBroker
class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
    @Override
    public void configureMessageBroker(MessageBrokerRegistry config) {
        config.enableSimpleBroker("/topic");
        config.setApplicationDestinationPrefixes("/app");
    }
    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/ws").withSockJS();
    }
}

@Controller
class ChatController {
    private final SimpMessageSendingOperations messagingTemplate;

    public ChatController(SimpMessageSendingOperations messagingTemplate) {
        this.messagingTemplate = messagingTemplate;
    }

    @MessageMapping("/chat.sendMessage")
    public void sendMessage(@Payload ChatMessage chatMessage) {
        System.out.println("Received CHAT message from " + chatMessage.getSender() + ": " + chatMessage.getContent());
        messagingTemplate.convertAndSend("/topic/public-chat", chatMessage);
    }

    @MessageMapping("/chat.addUser")
    public void addUser(@Payload ChatMessage chatMessage) {
        if (chatMessage.getType() == ChatMessage.MessageType.JOIN) {
            System.out.println(chatMessage.getSender() + " JOINED the chat!");
            messagingTemplate.convertAndSend("/topic/public-chat", chatMessage);
        }
    }
}

@SpringBootApplication
public class Main {
    public static void main(String[] args) {
        SpringApplication.run(Main.class, args);
        System.out.println("\n--- Spring Boot Chat Server Started with JOIN handling ---");
        System.out.println("Connect to ws://localhost:8080/ws");
        System.out.println("Send JOIN messages to /app/chat.addUser");
        System.out.println("Send CHAT messages to /app/chat.sendMessage");
        System.out.println("Subscribe to /topic/public-chat");
    }
}

Client: Connect & Subscribe

On the client-side (e.g., using JavaScript and SockJS/STOMP.js), the first step is to establish a WebSocket connection and then subscribe to the public chat topic.

The client uses the STOMP client to connect to the /ws endpoint and then subscribes to /topic/public-chat to receive all broadcast messages.

// Assuming SockJS and STOMP.js are loaded
var socket = new SockJS('/ws'); // Connect to our WebSocket endpoint
var stompClient = Stomp.over(socket);

stompClient.connect({}, function(frame) {
    console.log('Connected: ' + frame);
    // Subscribe to the public chat topic
    stompClient.subscribe('/topic/public-chat', function(message) {
        var chatMessage = JSON.parse(message.body);
        console.log('Received message: ' + chatMessage.content + ' from ' + chatMessage.sender);
        // Update UI with the message
    });

    // Send a JOIN message (example)
    stompClient.send("/app/chat.addUser", {}, JSON.stringify({
        sender: 'User123',
        type: 'JOIN'
    }));
});

Client: Sending Chat Messages

Once connected and subscribed, clients can send chat messages to the server. These messages are sent to the application destination (e.g., /app/chat.sendMessage) that our Spring controller is listening to.

The server then processes this message and broadcasts it back to all subscribers of /topic/public-chat, including the sender.

// Function to send a chat message
function sendChatMessage(senderName, messageContent) {
    if (stompClient && stompClient.connected) {
        var chatMessage = {
            sender: senderName,
            content: messageContent,
            type: 'CHAT'
        };
        stompClient.send("/app/chat.sendMessage", {}, JSON.stringify(chatMessage));
        console.log("Sent: " + chatMessage.content);
    } else {
        console.log("STOMP client not connected.");
    }
}

// Example usage:
// sendChatMessage('Alice', 'Hello everyone!');

The Full Chat Flow

Let's visualize the complete flow for a public chat room:

Client Connects: A user's browser connects to the WebSocket endpoint (/ws).
Client Subscribes: The client subscribes to the public topic (/topic/public-chat) to receive messages.
Client Joins: The client sends a JOIN message to the server (/app/chat.addUser).
Server Broadcasts Join: The server receives the JOIN message and broadcasts it to /topic/public-chat. All clients receive the "user joined" notification.
Client Sends Chat: A client sends a CHAT message to the server (/app/chat.sendMessage).
Server Broadcasts Chat: The server receives the CHAT message and broadcasts it to /topic/public-chat. All clients receive the chat message.

Public Chat Best Practices

When building public chat rooms, consider these points for a better user experience and server performance:

Message History: Implement a way to store and retrieve past messages for new users joining the room.
User Presence: Track active users in a room (e.g., using an in-memory map or a database).
Rate Limiting: Prevent spamming by limiting how frequently a user can send messages.
Moderation: Provide tools for moderators to remove inappropriate messages or ban users.
Scalability: For large-scale public chats, consider external message brokers like RabbitMQ or Kafka.

Public Chat Room Check

Which of the following are true about implementing public chat rooms using Spring WebSockets and STOMP?

Recap: Public Chat Rooms

In this lesson, you learned how to implement public, broadcast-style chat rooms using Spring WebSockets and STOMP.

We saw how STOMP topics (e.g., /topic/public-chat) serve as the channels for rooms.
You learned to use @MessageMapping and SimpMessageSendingOperations on the server to handle incoming messages and broadcast them.
We explored how to handle user join events and notify all participants.
Finally, we touched upon client-side interaction and important best practices for robust chat applications.

Next, we'll dive into implementing private, one-on-one messaging!

Często zadawane pytania

Czy lekcja „Implementowanie publicznych pokojów czatu” jest bezpłatna?

Tak — pełny tekst „Implementowanie publicznych pokojów czatu” jest dostępny za darmo tutaj w sieci. Aby ćwiczyć ją interaktywnie (wbudowany edytor kodu i tutor AI dostępny 24/7) i odblokować resztę kursu WebSockets & Real-Time Systems with Spring, przejdź na CoddyKit PRO. Kurs WebSockets & Real-Time Systems with Spring zawiera 4 lekcji w sumie.

Co nauczysz się w „Implementowanie publicznych pokojów czatu”?

Proszę opracować funkcjonalność umożliwiającą użytkownikom dołączanie do publicznych pokojów czatu i uczestniczenie w rozmowach w formie transmisji. Ćwiczysz WebSockets & Real-Time Systems with Spring z praktycznym kodem, który uruchamiasz bezpośrednio w przeglądarce, a tutor AI dostępny 24/7 odpowiada na Twoje pytania podczas pracy nad lekcją.

Czy potrzebuję doświadczenia, aby zacząć WebSockets & Real-Time Systems with Spring?

Nie wymagamy żadnego doświadczenia. WebSockets & Real-Time Systems with Spring w CoddyKit jest strukturyzowany dla początkujących i zaawansowanych użytkowników, więc możesz zacząć tutaj lub od początku i uczyć się w swoim tempie. To lekcja 2 z 4.

Ile czasu zajmuje lekcja „Implementowanie publicznych pokojów czatu”?

Większość lekcji CoddyKit trwa około 5–10 minut. Każda lekcja to mały, interaktywny krok, dzięki czemu robisz systematyczne postępy i zawsze wracasz dokładnie do tego samego miejsca — na webie i w aplikacji.

Czy mogę pisać i uruchamiać kod w tej lekcji WebSockets & Real-Time Systems with Spring?

Tak. Każda lekcja WebSockets & Real-Time Systems with Spring zawiera wbudowany edytor kodu, więc piszesz i uruchamiasz prawdziwy kod bezpośrednio w przeglądarce i od razu otrzymujesz sprzężenie zwrotne od AI — bez konfiguracji na komputerze.

Wszystkie lekcje w tym kursie

Projektowanie modelu wiadomości czatu
Implementowanie publicznych pokojów czatu
Prywatne wiadomości z użyciem STOMP
Wskaźniki pisania i obecność online

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