Question

我尝试编写动作来生成图片的拇指，并向用户显示它是否尚未生成。问题是：生成部分在异步中运行，并在生成部分完成之前显示部分代码。我是Scala和Play Framework的新手，无法让show等待。我试过这样的话：

def thumbs(profiletype: String, id: Int, filename: String, extention: String) = Action {
val content = File.getBinaryContent(pathToDir + filename + "." + extention)
content match {
  case Some(c) => Ok(c).as(File.getContentType(extention))
  case _ => val picture = Picture.getById(id)
      picture match {
        case None => NotFound("Page not found")
        case Some(p) => val rslt = Future (p.generateThumbs(pathToDir, profiletype))
          val r=rslt.map(a=>a)
          Await.ready(r, Duration(8, "second"))
            Logger.debug(pathToDir + filename + "." + extention)
            val content = File.getBinaryContent(pathToDir + filename + "." + extention)
            renderBinary(content, File.getContentType(extention))}
          }
}

并且喜欢这样没有运气

def thumbs(profiletype: String, id: Int, filename: String, extention: String) = Action {
val content = File.getBinaryContent(pathToDir + filename + "." + extention)
content match {
  case Some(c) => Ok(c).as(File.getContentType(extention))
  case _ => val picture = Picture.getById(id)
      picture match {
        case None => NotFound("Page not found")
        case Some(p) => val rslt = Future (p.generateThumbs(pathToDir, profiletype))
          Await.ready(rslt, Duration(8, "second"))
            Logger.debug(pathToDir + filename + "." + extention)
            val content = File.getBinaryContent(pathToDir + filename + "." + extention)
            renderBinary(content, File.getContentType(extention))}
          }
}

此Await不起作用，并且在p.generateThumbs完成之前记录日志

Answer 1

您可以return a Future[Result]使用Await.ready或Await.result，而不是在等待生成缩位条之前异步生成缩略图并阻塞（{3}}或Option）。

在你的情况下，这看起来像（未经测试）：
（我还将您的map模式匹配转换为getOrElse和def thumbs( profiletype: String, id: Int, filename: String, extention: String ) = Action.async { // return an (explicit) asynchronous result val filepath = pathToDir + filename + "." + extention File.getBinaryContent(filepath) .map ( content => // we found the thumbnail, return its content as a Future[Result] Future.successful(Ok(content).as(File.getContentType(extention))) ) .getOrElse { // we have not found the thumbnail, check if the Picture exists Picture.getById(id) .map { picture => // we found the Picture, lets generate the thumbnails Future(picture.generateThumbs(pathToDir, profiletype)) .map { futureResult => // the thumbnails are created // return the content of the thumbnail // and since we are in a Future.map this will be a Future[Result] Logger.debug(filepath) val content = File.getBinaryContent(filepath) renderBinary(content, File.getContentType(extention)) } } // we could not find the Picture return a NotFound as Future[Result] .getOrElse(Future.successful(NotFound("Page not found"))) } }函数。）

println("Tag of button: \(button.tag)")

这样我们只有一个阻塞线程，创建缩略图而不是两个，一个创建缩略图，一个等到第一个线程完成创建缩略图。

播放可以在创建缩略图时提供其他请求，创建缩略图后播放将使用缩略图进行响应。

如何在Play Framework 2控制器操作中等待？

1 个答案: