HttpClient 302 重定向

Question

我有 2 个网址：https://pcr.apple.com/id868222886 和 https://jigsaw.w3.org/HTTP/300/302.html。两者都有位置 link 和 302 响应代码。

using System;
using System.IO;
using System.Net.Http;

namespace XaveScor.PodcastFeed
{
    public class RemoteFeedSource: FeedSource
    {
        private string url;
        protected virtual HttpMessageHandler Handler => new HttpClientHandler() { AllowAutoRedirect = true };

        public override Stream Stream => client.Value.GetStreamAsync(url).Result;

        private readonly Lazy<HttpClient> client;

        public RemoteFeedSource(string url)
        {
            client = new Lazy<HttpClient>(() => new HttpClient(Handler), false);    
            this.url = url;
        }
    }
}


[TestMethod]
public void Test1() //fail
{
    var source = new RemoteFeedSource("https://pcr.apple.com/id868222886");
    Assert.AreNotEqual(source.Stream.GetString(), "");
}

[TestMethod]
public void Test2() //success
{
    var source = new RemoteFeedSource("https://jigsaw.w3.org/HTTP/300/302.html");
    Assert.AreNotEqual(source.Stream.GetString(), "");
}

为什么？有什么区别？

Answer 1

如果您查看响应中的 headers，您会看到：

第一个 (https://pcr.apple.com/id868222886):

Content-Length: 0
Location: http://beardycast.libsyn.com/rss

第二个（https://jigsaw.w3.org/HTTP/300/302.html）：

Content-Length: 389
Content-Type:   text/html;charset=ISO-8859-1
Location:       https://jigsaw.w3.org/HTTP/300/Overview.html

所以第一个服务器静静地重定向你，第二个服务器为你提供一些额外的headers：

Strict-Transport-Security: max-age=15552015; includeSubDomains; preload
Public-Key-Pins: pin-sha256="cN0QSpPIkuwpT6iP2YjEo1bEwGpH/yiUn6yhdy+HNto="; pin-sha256="WGJkyYjx1QMdMe0UqlyOKXtydPDVrk7sl2fV+nNm1r4="; pin-sha256="LrKdTxZLRTvyHM4/atX2nquX9BeHRZMCxg3cf4rhc2I="; max-age=864000
X-Frame-Options: deny
X-XSS-Protection: 1; mode=block

响应body：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
               "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
 <title>Moved</title>
</head>
<body>
<P>This resources has moved, click on the link if your browser doesn't support automatic redirection<BR>
<A HREF="http://jigsaw.w3.org/HTTP/300/Overview.html">http://jigsaw.w3.org/HTTP/300/Overview.html</A></body>
</html>

这就是为什么 HttpClient returns non-empty 结果字符串 - 它不是真正的空。您的单元测试有错误的设计方法，因为它们不检查状态，但只检查响应长度，即使对于 3** 个 http 状态代码，响应长度也可能是 non-empty。

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