如何在Jetty 9中訪問實例化的WebSocket？

Question

這可能很明顯，但是我對這種范例是陌生的。 我創建一個Jetty服務器並注冊我的websocket類，如下所示：

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

websocket收到消息很好。 我還希望能夠先從服務器發送消息，而無需先從客戶端接收消息。 如何打開連接打開時創建的MyEchoSocket實例？ 或者，更一般而言，如何在MyEchoSocket中的onText方法之外的套接字上發送消息？

Answer 1

在超級簡化的聊天室概念中介紹了兩種常用技術。

選項1：讓WebSocket將其狀態報告回中央位置

@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，只需使用中心位置即可與您選擇的websocket通信。

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

// or

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

選項2：使用WebSocketCreator手動創建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));
    }
}

此時，您可以使用與上述相同的技術來與您選擇的websocket通信。