向特定用户定向发送消息
使用用户目标地址、@SendToUser 和 SimpMessagingTemplate.convertAndSendToUser，通过 STOMP 发送私有的、面向单个用户的消息。
向特定用户定向发送消息 是 CoddyKit 上的免费 WebSockets & Real-Time Systems with Spring 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 WebSockets & Real-Time Systems with Spring 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 WebSockets & Real-Time Systems with Spring 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Beyond Broadcasts
So far messages went to a /topic that every subscriber receives. Real apps also need private messages: a chat whisper, a personal notification, an order update for one customer.
User Destinations
Spring supports the /user destination prefix. When a client subscribes to /user/queue/notifications, Spring rewrites it to a unique, per-session queue so only that user gets the message.
Where the Principal Comes From
Targeted messaging needs to know who a session is. The Principal attached during the handshake (from Spring Security or a custom handshake handler) provides the username key.
Sending with @SendToUser
In a controller method you annotate with @SendToUser. The return value is delivered only to the user who sent the triggering message.
@MessageMapping("/private")
@SendToUser("/queue/reply")
public Note handle(Note in, Principal principal) {
return new Note("Hi " + principal.getName());
}The Client Subscription
The client subscribes to the /user-prefixed destination. Spring resolves it to that client's private queue automatically.
stompClient.subscribe('/user/queue/reply', (msg) => {
console.log('Private:', JSON.parse(msg.body));
});Pushing from Anywhere with the Template
Outside a controller (e.g. from a service or scheduled job) use SimpMessagingTemplate.convertAndSendToUser to reach a specific user by name.
messagingTemplate.convertAndSendToUser(
"alice", "/queue/notifications", new Alert("Payment received"));How Resolution Works
The UserDestinationMessageHandler maps /user/{username}/queue/x to the actual session-specific destination. You address users by name; Spring finds their active sessions.
Multiple Sessions per User
One user may be connected from a phone and a laptop. convertAndSendToUser delivers to all of that user's active sessions, so notifications appear everywhere they are logged in.
Targeting a Single Session
To reach just one device, pass headers selecting a specific simpSessionId rather than broadcasting to every session of the user.
SimpMessageHeaderAccessor h = SimpMessageHeaderAccessor.create(SimpMessageType.MESSAGE);
h.setSessionId(sessionId);
h.setLeaveMutable(true);
messagingTemplate.convertAndSendToUser(user, "/queue/reply", body, h.getMessageHeaders());User Destinations Across a Cluster
With a single server the simple broker resolves user destinations in-memory. Across multiple nodes you need an external broker (RabbitMQ) plus a UserRegistry broadcast so a node can route to a user connected elsewhere.
Security Note
Never let a client choose another user's destination. Always derive the target from the authenticated Principal, not from client-supplied data, to prevent message hijacking.
Quick Check
Test your knowledge of per-user messaging.
Recap
You delivered private messages:
- The
/userprefix maps to per-session queues @SendToUserreplies to the originating userconvertAndSendToUserpushes to a named user from anywhere- Multiple sessions per user are reached together; target one with session headers
- Always derive the target from the authenticated
Principal
用 AI 导师学习 WebSockets & Real-Time Systems with Spring — 免费
在浏览器中编写并运行真实代码，获得全天候 AI 导师的即时帮助，并在网页或应用中继续学习。
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常见问题解答
「向特定用户定向发送消息」课时是免费的吗？
是的 — 「向特定用户定向发送消息」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 WebSockets & Real-Time Systems with Spring 课程的其余内容，请升级到 CoddyKit PRO。 WebSockets & Real-Time Systems with Spring 课程共包含 4 节课。
「向特定用户定向发送消息」这节课中我会学到什么？
使用用户目标地址、@SendToUser 和 SimpMessagingTemplate.convertAndSendToUser，通过 STOMP 发送私有的、面向单个用户的消息。 你通过在浏览器中直接运行的动手代码来练习 WebSockets & Real-Time Systems with Spring，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 WebSockets & Real-Time Systems with Spring 需要有经验吗？
无需任何先前经验。CoddyKit 上的 WebSockets & Real-Time Systems with Spring 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「向特定用户定向发送消息」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 WebSockets & Real-Time Systems with Spring 课中编写并运行代码吗？
能。每节 WebSockets & Real-Time Systems with Spring 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。
此课程中的所有课时
- WebSocket 拦截器
- 自定义消息转换器
- 用户会话管理
- 向特定用户定向发送消息