如何在 Jetty 9 中访问实例化的 WebSockets? [英] How do I access instantiated WebSockets in Jetty 9?

问题描述

这可能是显而易见的，但我对这种范式还不熟悉.我创建了一个 Jetty 服务器并注册了我的 websocket 类，如下所示:

This is probably obvious, but I am new to this paradigm. I create a Jetty Server and register my websocket class as follows:

        Server server = new Server(8080);
        WebSocketHandler wsHandler = new WebSocketHandler()
        {
            @Override
            public void configure(WebSocketServletFactory factory)
            {
                factory.register(MyEchoSocket.class);
            }
        };
        server.setHandler(wsHandler);

websocket 接收消息正常.我还希望能够在没有首先从客户端收到消息的情况下从服务器发送消息.如何访问连接打开时创建的 MyEchoSocket 实例?或者，更一般地说，我如何在 MyEchoSocket 中的 onText 方法之外的套接字上发送消息?

The websocket receives messages fine. I would like to also be able to send messages out from the server without having first received a message from the client. How do I access the MyEchoSocket instance that's created when the connection opens? Or, more generally, how do I send messages on the socket outside of the onText method in MyEchoSocket?

推荐答案

两种常用技术，在此以超级简化的聊天室概念呈现.

Two common techniques, presented here in a super simplified chatroom concept.

选项 #1:让 WebSocket 将其状态报告给中央位置

@WebSocket
public class ChatSocket {
    public Session session;

    @OnWebSocketConnect
    public void onConnect(Session session) {
        this.session = session;
        ChatRoom.getInstance().join(this);
    }

    @OnWebSocketMessage
    public void onText(String message) {
        ChatRoom.getInstance().writeAllMembers("Hello all");
    }

    @OnWebSocketClose
    public void onClose(int statusCode, String reason) {
        ChatRoom.getInstance().part(this);
    }
}

public class ChatRoom {
    private static final ChatRoom INSTANCE = new ChatRoom();

    public static ChatRoom getInstance()
    {
        return INSTANCE;
    }

    private List<ChatSocket> members = new ArrayList<>();

    public void join(ChatSocket socket) 
    {
        members.add(socket);
    }

    public void part(ChatSocket socket) 
    {
        members.remove(socket);
    }

    public void writeAllMembers(String message) 
    {
        for(ChatSocket member: members)
        {
            member.session.getRemote().sendStringByFuture(message);
        }
    }

    public void writeSpecificMember(String memberName, String message) 
    {
        ChatSocket member = findMemberByName(memberName);
        member.session.getRemote().sendStringByFuture(message);
    }

    public ChatSocket findMemberByName(String memberName) 
    {
        // left as exercise to reader
    }
}

然后只需使用中心位置与您选择的 websocket 对话.

Then simply use the central location to talk to the websockets of your choice.

ChatRoom.getInstance().writeSpecificMember("alex", "Hello");

// or

ChatRoom.getInstance().writeAllMembers("Hello all");

选项 2:使用 WebSocketCreator 手动创建 WebSocket

@WebSocket
public class ChatSocket {
    public ChatRoom chatroom;

    public ChatSocket(ChatRoom chatroom)
    {
        this.chatroom = chatroom;
    }

    @OnWebSocketConnect
    public void onConnect(Session session) {
        chatroom.join(this);
    }

    @OnWebSocketMessage
    public void onText(String message) {
        chatroom.writeAllMembers(message);
    }

    @OnWebSocketClose
    public void onClose(int statusCode, String reason) {
        chatroom.part(this);
    }
}

public class ChatCreator implements WebSocketCreator
{
    private ChatRoom chatroom;

    public ChatCreator(ChatRoom chatroom)
    {
        this.chatroom = chatroom;
    }

    public Object createWebSocket(UpgradeRequest request, 
                                  UpgradeResponse response)
    {
        // We want to create the Chat Socket and associate
        // it with our chatroom implementation
        return new ChatSocket(chatroom);
    }
}

public class ChatHandler extends WebSocketHandler
{
    private ChatRoom chatroom = new ChatRoom();

    @Override
    public void configure(WebSocketServletFactory factory)
    {
        factory.setCreator(new ChatCreator(chatroom));
    }
}

此时，您可以使用与上述相同的技术与您选择的 websocket 通信.

At this point you can use the same techniques as above to talk to the websockets of your choice.

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