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How to use Java Websocket to implement a multi-player online editor?

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Dec 02, 2023 pm 01:17 PM

javawebsocketMultiplayer online editor

如何使用Java Websocket实现多人在线编辑器？

How to use Java Websocket to implement a multi-player online editor?

With the rapid development of the Internet, the need for real-time sharing of documents and editing is becoming more and more common. Multi-person online editors have become an important part of modern office and collaboration tools due to their real-time and collaborative editing characteristics. This article will introduce how to use Java Websocket to implement a simple multi-person online editor, allowing multiple users to collaboratively edit the same document in real time.

Java Websocket is part of Java EE 7. It provides a two-way communication protocol that can establish a persistent connection between the client and the server to achieve real-time communication. In our scenario, we will use Java Websocket to implement the function of updating document content, cursor position, and editing status in real time.

First, we need to create a Java Websocket server. You can use Java EE's standard API, or you can use third-party libraries such as Tyrus. The following is a code example using Tyrus:

import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

@ServerEndpoint(value = "/editor")
public class EditorWebSocketServer {

    private static Map<Session, String> users = new ConcurrentHashMap<>();

    private static Set<Session> sessions = Collections.newSetFromMap(new ConcurrentHashMap<>());

    @OnOpen
    public void onOpen(Session session) throws IOException {
        sessions.add(session);
    }

    @OnMessage
    public void onMessage(String message, Session session) throws IOException {
        // 处理客户端发送的消息
        String[] parts = message.split(":");
        String action = parts[0];
        String content = parts[1];

        if (action.equals("login")) {
            users.put(session, content);
            broadcast("login:" + content);
        } else if (action.equals("content")) {
            broadcast("content:" + content);
        } else if (action.equals("cursor")) {
            broadcast("cursor:" + content);
        } else if (action.equals("state")) {
            broadcast("state:" + content);
        }
    }

    @OnClose
    public void onClose(Session session) throws IOException {
        sessions.remove(session);
        String username = users.get(session);
        users.remove(session);
        broadcast("logout:" + username);
    }

    private void broadcast(String message) throws IOException {
        for (Session session : sessions) {
            session.getBasicRemote().sendText(message);
        }
    }
}

In the above code, we use the @ServerEndpoint annotation to mark a WebSocket entry point and define several @OnXXXAnnotated methods to handle client connections, messages and closing events. users is a mapping table that stores connected users, and sessions is a collection that stores all connections. In the onOpen() method, we add the newly connected Session object to the sessions collection. In the onMessage() method, we handle different operation types and broadcast the received message to all connected clients through the broadcast() method. In the onClose() method, we remove the user whose connection is closed from the sessions collection and notify other users.

The server-side part has been completed. Next, we need to create a simple front-end page to display and test the function of the multiplayer online editor. The following is a sample code for a simple HTML page:

<!DOCTYPE html>
<html>
<body>
    <textarea id="content"></textarea>
    <p>在线用户:</p>
    <ul id="users"></ul>

    <script>
        const socket = new WebSocket("ws://localhost:8080/editor");

        socket.onopen = function(event) {
            // 客户端连接成功后，发送用户名
            const username = prompt("请输入用户名");
            socket.send("login:" + username);
        }

        socket.onmessage = function(event) {
            // 处理服务器发送的消息
            const message = event.data;
            const parts = message.split(":");
            const action = parts[0];
            const content = parts[1];

            if (action === "login") {
                // 有新用户加入
                const user = document.createElement("li");
                user.textContent = content;
                document.getElementById("users").appendChild(user);
            } else if (action === "content") {
                // 更新文本内容
                document.getElementById("content").value = content;
            } else if (action === "cursor") {
                // 处理其他用户的光标位置变化
                // TODO
            } else if (action === "state") {
                // 处理其他用户的编辑状态变化
                // TODO
            } else if (action === "logout") {
                // 有用户退出
                const users = document.getElementById("users");
                const user = Array.from(users.children).find(u => u.textContent === content);
                users.removeChild(user);
            }
        }

        document.getElementById("content").addEventListener("input", function() {
            // 监听文本内容变化事件
            const content = this.value;
            socket.send("content:" + content);
        });
    </script>
</body>
</html>

In the above code, we use new WebSocket() to create a connection with the server side, and onopen Send the username in the callback function. In the onmessage callback function, we process different types of messages sent by the server and update the user list and text content on the page. When the text content changes, we send the content operation and the changed text content through the send() method.

The above are the basic steps and code examples for using Java Websocket to implement a multi-player online editor. Through the collaboration between Java Websocket and front-end pages, we can realize the function of multiple users collaboratively editing the same document in real time. Of course, the sample code still has many areas that need to be improved and expanded, such as handling changes in the user's cursor position and editing status, supporting real-time saving and restoring documents, etc. I hope this article can help everyone understand and use Java Websocket to implement a multi-player online editor.

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