我正在使用Play 2.0.1和Java.
到目前为止,我已经使用Promise加载了一个显示数据库数据的页面.
这是最初的Controller代码:
public static Result index() { // Generate the page final MainPage page = new MainPage(); Promise<MainPage> promiseMainPage = Akka.future( new Callable<MainPage>() { public MainPage call() throws Exception { page.generate(); return page; } }); return async(promiseMainPage.map(new Function<MainPage, Result>() { @Override public Result apply(MainPage mainPage) throws Throwable { return ok(views.html.index.render(mainPage)); } })); }
这一切都很好;承诺的页面发送到浏览器,而服务器不阻止数据库查询(在page.generate()中执行)完成.
但是,现在我想使用WebSocket来更新从数据库中检索到的新/修改信息的页面.
所以我使用Chat示例来做到这一点(甚至简化,因为我只想使用传出通道:服务器到客户端).我已将以下内容添加到index.scala.html的末尾:
<script type="text/javascript" charset="utf-8"> $(function() { var WS = window['MozWebSocket'] ? MozWebSocket : WebSocket; var socket = new WS("@(routes.Application.webSocket().webSocketURL(request))"); var receiveEvent = function(event) { var data = JSON.parse(event.data); var connectionStatus = data["connectionStatus"]; var connectionStatusHtml = '<font color="red">* Not connected</font>'; if (connectionStatus != undefined) { connectionStatusHtml = '<font color="blue">' + connectionStatus + '</font>'; } $('#connectionStatus').html(connectionStatusHtml); } socket.onmessage = receiveEvent; }) </script>
我已经更新了路由文件并为webSocket()请求创建了一个处理程序.
此时,当我尝试浏览页面时,我从播放中收到以下错误:
[error] play - Waiting for a promise, but got an error: null java.lang.RuntimeException: null at play.libs.F$Promise$2.apply(F.java:113) ~[play_2.9.1.jar:2.0.1] at akka.dispatch.Future$$anonfun$map$1.liftedTree3$1(Future.scala:625) ~[akka-actor.jar:2.0.1] at akka.dispatch.Future$$anonfun$map$1.apply(Future.scala:624) ~[akka-actor.jar:2.0.1] at akka.dispatch.Future$$anonfun$map$1.apply(Future.scala:621) ~[akka-actor.jar:2.0.1] at akka.dispatch.DefaultPromise.akka$dispatch$DefaultPromise$$notifyCompleted(Future.scala:943) [akka-actor.jar:2.0.1] at akka.dispatch.DefaultPromise$$anonfun$tryComplete$1$$anonfun$apply$mcV$sp$4.apply(Future.scala:920) [akka-actor.jar:2.0.1]
这发生在返回ok(views.html.index.render(mainPage));.
从HTML文件中注释掉脚本可以解决这个问题,但当然不会打开WebSocket.
是否可以在Play中结合使用Promise和WebSocket?也许我想念用它?