sto cercando di capire meglio come funziona il seguente Spring MVC 3.2 applicazione: https://github.com/rstoyanchev/spring-mvc-chatCapire classe DeferredResult del Spring MVC nel contesto dell'applicazione primavera-MVC-Chat github
La mia domanda riguarda il deferredResult Spring MVC class. Ho notato che in un dato momento ci sono tante voci nella mappa chatRequests
in quanto vi sono utenti connessi all'applicazione di chat.
Dire che ci sono 3 utenti connessi all'applicazione di chat. Vedrai che quando l'utente n. invia un messaggio (vedi metodo postMessage in basso), quindi il ciclo for (nel metodo postMessage) itera tre volte. Non riesco a capire perché sia così.
Ho incluso il seguente codice di esempio.
Codice per il regolatore:
@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);
}
}
}
codice Javascript:
$(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());
});
e html pagina:
<!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>
Beh, immagino che se hai discusso di questo con l'autore di "DeferredResult", dovresti posizionare l'intera comunicazione in qualche posto. In modo che tutti possano sapere di più su di esso. – rd22
Penso che [questa serie di diapositive] (http://rstoyanchev.github.io/spring-mvc-32-update/#8) di Rossen Stoyanchev metta in luce anche l'argomento. –