Das Verständnis der Spring MVC ist DeferredResult Klasse im Rahmen des spring-mvc-chat github-Anwendung

Ich versuche zu verstehen, wie die folgende spring mvc 3.2-Anwendung funktioniert: https://github.com/rstoyanchev/spring-mvc-chat

Meine Frage ist über die deferredResult Spring MVC Klasse. Ich habe bemerkt, dass zu einem gegebenen Zeitpunkt gibt es viele Einträge in der chatRequests Karte als Benutzer eine Verbindung zum chat-Anwendung.

Sagen, es gibt 3 Benutzer verbunden um die chat-Anwendung. Sie werden sehen, dass, wenn user #3 sendet eine Nachricht (siehe postMessage-Methode unten), dann die for-Schleife (in der postMessage-Methode) wiederholt dreimal. Ich kann nicht herausfinden, warum das so ist.

Ich bin auch Beispiel-code unten.

Code für controller:

@Controller
@RequestMapping("/mvc/chat")
public class ChatController {

    private final ChatRepository chatRepository;
    private final Map<DeferredResult<List<String>>, Integer> chatRequests = new ConcurrentHashMap<DeferredResult<List<String>>, Integer>();

    @Autowired
    public ChatController(ChatRepository chatRepository) {
        this.chatRepository = chatRepository;
    }

    @RequestMapping(method = RequestMethod.GET)
    @ResponseBody
    public DeferredResult<List<String>> getMessages(@RequestParam int messageIndex) {

        final DeferredResult<List<String>> deferredResult = new DeferredResult<List<String>>(null, Collections.emptyList());
        this.chatRequests.put(deferredResult, messageIndex);

        deferredResult.onCompletion(new Runnable() {
            @Override
            public void run() {
                chatRequests.remove(deferredResult);
            }
        });

        List<String> messages = this.chatRepository.getMessages(messageIndex);
        if (!messages.isEmpty()) {
            deferredResult.setResult(messages);
        }

        return deferredResult;
    }

    @RequestMapping(method = RequestMethod.POST)
    @ResponseBody
    public void postMessage(@RequestParam String message) {

        this.chatRepository.addMessage(message);

        //Update all chat requests as part of the POST request
        //See Redis branch for a more sophisticated, non-blocking approach

        for (Entry<DeferredResult<List<String>>, Integer> entry : this.chatRequests.entrySet()) {
            List<String> messages = this.chatRepository.getMessages(entry.getValue());
            entry.getKey().setResult(messages);
        }
    }
}

Javascript-code:

$(document).ready(function() {

    function ChatViewModel() {

        var that = this;

        that.userName = ko.observable('');
        that.chatContent = ko.observable('');
        that.message = ko.observable('');
        that.messageIndex = ko.observable(0);
        that.activePollingXhr = ko.observable(null);


        var keepPolling = false;

        that.joinChat = function() {
            if (that.userName().trim() != '') {
                keepPolling = true;
                pollForMessages();
            }
        }

        function pollForMessages() {
            if (!keepPolling) {
                return;
            }
            var form = $("#joinChatForm");


            that.activePollingXhr($.ajax({url: form.attr("action"), type: "GET", data: form.serialize(), cache: false,
                success: function(messages) {
                    console.log(messages);
                    for (var i = 0; i < messages.length; i++) {
                        that.chatContent(that.chatContent() + messages[i] + "\n");
                        that.messageIndex(that.messageIndex() + 1);
                    }
                },
                error: function(xhr) {
                    if (xhr.statusText != "abort" && xhr.status != 503) {
                        resetUI();
                        console.error("Unable to retrieve chat messages. Chat ended.");
                    }
                },
                complete: pollForMessages
            }));
            $('#message').focus();
        }

        that.postMessage = function() {
            if (that.message().trim() != '') {
                var form = $("#postMessageForm");
                $.ajax({url: form.attr("action"), type: "POST",
                    data: "message=[" + that.userName() + "] " + $("#postMessageForm input[name=message]").val(),
                    error: function(xhr) {
                        console.error("Error posting chat message: status=" + xhr.status + ", statusText=" + xhr.statusText);
                    }
                });
                that.message('');
            }
        }

        that.leaveChat = function() {
            that.activePollingXhr(null);
            resetUI();
            this.userName('');
        }

        function resetUI() {
            keepPolling = false;
            that.activePollingXhr(null);
            that.message('');
            that.messageIndex(0);
            that.chatContent('');
        }

    }

    //Activate knockout.js
    ko.applyBindings(new ChatViewModel());

});

- und html-Seite:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org">
<head>
    <title>Chat</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
    <h1>Chat</h1>

    <form id="joinChatForm" th:action="@{/mvc/chat}" data-bind="visible: activePollingXhr() == null">
        <p>
            <label for="user">User: </label>
            <input id="user" name="user" type="text" data-bind="value: userName"/>
            <input name="messageIndex" type="hidden" data-bind="value: messageIndex"/>
            <button id="start" type="submit" data-bind="click: joinChat">Join Chat</button>
        </p>
    </form>

    <form id="leaveChatForm" th:action="@{/mvc/chat}" data-bind="visible: activePollingXhr() != null">
        <p>
            You're chatting as <strong data-bind="text: userName"></strong>
            <button id="leave" type="submit" data-bind="click: leaveChat">Leave Chat</button>
        </p>
    </form>

    <div data-bind="visible: activePollingXhr() != null">
        <textarea rows="15" cols="60" readonly="readonly" data-bind="text: chatContent"></textarea>
    </div>

    <form id="postMessageForm" th:action="@{/mvc/chat}" data-bind="visible: activePollingXhr() != null">
        <p>
            <input id="message" name="message" type="text" data-bind="value: message" />
            <button id="post" type="submit" data-bind="click: postMessage">Post</button>
        </p>
    </form>
</body>
<script type="text/javascript" src="../../../resources/js/jquery-1.7.2.min.js" th:src="@{/resources/js/jquery-1.7.2.min.js}"></script>
<script type="text/javascript" src="../../../resources/js/knockout-2.0.0.js" th:src="@{/resources/js/knockout-2.0.0.js}"></script>
<script type="text/javascript" src="../../../resources/js/chat.js" th:src="@{/resources/js/chat.js}"></script>

</html>