Question

我到处寻找我的问题的答案，但我没有找到我想知道的。

这是我想要做的：我有一个来自同一域和其他域的图像，pdf或html页面的URL。可以下载＆＃34;下载＆＃34;他们用AJAX？但是我不想让它们在我的服务器上或其他任何地方使用它们，我只是想直接在我的网站上使用它们而不必再次上传它们（为了节省时间）。

我也遇到了一些麻烦＆＃34; XMLHttpRequest.getAllResponseHeaders（）＆＃34;当内容来自其他域时。我尝试使用倍数网址。我没有收到任何东西：＆＃34;＆＃34;。这是正常的吗？

感谢您的帮助！：）

Answer 1

Unfortunately it is impossible to make AJAX requests for resources on domains external to the website's host domain, edit: unless they implement a workaround, like CORS or JSONP. I recommend doing some reading on Cross Origin Resource Sharing for more details.

As for resources on the same domain, you'd be storing those on your server anyway - you'd have to, in fact, because by its very nature it would be a part of your site. If you describe what you're trying to implement specifically (perhaps post a jsfiddle with your code), we could find a solution to your specific use case. Hope this helps.

Answer 2

[...] image, pdf or html page [...]

The types of these requests are very different. What you mean with 'download' is a little ambigious. If you're requesting a file via AJAX, this loads the value into a variable. It doesn't save the file to your computer.

[...] I received nothing: "" Is it normal? [...]

Yes, if the remote server isn't the same as you're currently on (also the same port) and also doesn't support CORS (cross-domain requests), the result will be blank.

If it's not possible to alter the remote server's cross-domain policies [and you have the permission to use their services], you could write a PHP script on your server that acts as a proxy. But don't forget to secure it to prevent mis-use. Also keep in mind that such a script can raise your traffic dramatically, so this should only be "Plan B".

Answer 3

You certainly can fetch images and html pages with AJAX and display them on your webpages.

The issues you are having with the xmlHttpRequest.GetAllResponseHeaders is most likely caused by the same origin policy. The browser prohibits you from interacting with the loaded data from another domain.

The server you are fetching the data from has to explicitly indicate that it allows your domain to fetch and display his resources by setting the Access-Control-Allow-Origin response header to that of your domain.

A way arround this is by using a proxy and setting the header yourself.

Answer 4

The following boilerplate code ( basically taken from the jquery api page ) loads your gravatar image ( delivered in png format ) from the stackoverflow website into a callback parameter. As others have noted, the same origin policy applies to ajax requests ( The sample code therefore can onlybe successfully run from the stackoverflow site context, eg. by opening a js console on this page ).

$.ajax({
  method: "GET"
  , url: "https://www.gravatar.com/avatar/d85e0ad5243245aabe2d34a3c9a296a9?s=32&d=identicon&r=PG&f=1"
  , cache: false
  , beforeSend: function( xhr ) {
    xhr.overrideMimeType( "text/plain; charset=x-user-defined" );
  }
})
  .done(function( data ) {
    if ( console && console.log ) {
      console.log( "Length of data:", data.length );
      console.log( "Sample of data:", data.slice( 0, 100 ) );
    }
  });

使用JQuery通过AJAX获取文件

4 个答案: