403当尝试下载远程映像时

Question

我正在尝试从某些网址下载图片。对于某些图片，它工作正常，但对于其他图片，我会收到403错误。

例如，这个：http :
//blog.zenika.com/themes/Zenika/img/zenika.gif

此图片访问不需要任何身份验证。您可以在链接上单击自己，并使用200状态代码验证该链接可用于您的浏览器。

以下代码产生一个异常：new java.net.URL(url).openStream()。相同的是，org.apache.commons.io.FileUtils.copyURLToFile(new java.net.URL(url), tmp)它们openStream()在引擎盖下使用相同的方法。

java.io.IOException: Server returned HTTP response code: 403 for URL: http://blog.zenika.com/themes/Zenika/img/zenika.gif
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1626) ~[na:1.7.0_45]
at java.net.URL.openStream(URL.java:1037) ~[na:1.7.0_45]
at services.impl.DefaultStampleServiceComponent$RemoteImgUrlFilter$class.downloadAsTemporaryFile(DefaultStampleServiceComponent.scala:548) [classes/:na]
at services.impl.DefaultStampleServiceComponent$RemoteImgUrlFilter$class.services$impl$DefaultStampleServiceComponent$RemoteImgUrlFilter$$handleImageUrl(DefaultStampleServiceComponent.scala:523) [classes/:na]

我使用Scala / Play Framework开发。我尝试使用内置的AsyncHttpClient。

// TODO it could be better to use itetarees on the GET call becase I think AHC load the whole body in memory
WS.url(url).get.flatMap { res =>
  if (res.status >= 200 && res.status < 300) {
    val bodyStream = res.getAHCResponse.getResponseBodyAsStream
    val futureFile = TryUtils.tryToFuture(createTemporaryFile(bodyStream))
    play.api.Logger.info(s"Successfully downloaded file $filename with status code ${res.status}")
    futureFile
  } else {
    Future.failed(new RuntimeException(s"Download of file $filename returned status code ${res.status}"))
  }
} recover {
  case NonFatal(e) => throw new RuntimeException(s"Could not downloadAsTemporaryFile url=$url", e)
}

使用此AHC代码，它可以正常工作。有人可以解释这种现象，为什么我的URL.openStream()方法出现403错误？

Answer 1

如前所述，某些托管服务商使用诸如UserAgent之类的标头来防止这种入侵：

这不起作用：

   val urls = """http://blog.zenika.com/themes/Zenika/img/zenika.gif"""
  val url = new URL(urls)
  val urlConnection = url.openConnection() 
  val inputStream = urlConnection.getInputStream()
  val bufferedReader = new BufferedReader(new InputStreamReader(inputStream))

这有效：

val urls = """http://blog.zenika.com/themes/Zenika/img/zenika.gif"""
val url = new URL(urls)
val urlConnection = url.openConnection()   
urlConnection.setRequestProperty("User-Agent", """NING/1.0""") 
val inputStream = urlConnection.getInputStream()
val bufferedReader = new BufferedReader(new InputStreamReader(inputStream))