XML 解析返回带有换行符的字符串

Question

我正在尝试通过站点地图解析 XML，然后循环访问地址以获取 Go 中帖子的详细信息。但是我收到了这个奇怪的错误:

: first path segment in URL cannot contain colon

这是代码片段:

type SitemapIndex struct {
    Locations []Location `xml:"sitemap"`
}

type Location struct {
    Loc string `xml:"loc"`
}

func (l Location) String() string {
    return fmt.Sprintf(l.Loc)
}

func main() {
    resp, _ := http.Get("https://www.washingtonpost.com/news-sitemaps/index.xml")
    bytes, _ := ioutil.ReadAll(resp.Body)
    var s SitemapIndex
    xml.Unmarshal(bytes, &s)
    for _, Location := range s.Locations {
        fmt.Printf("Location: %s", Location.Loc)
        resp, err := http.Get(Location.Loc)
        fmt.Println("resp", resp)
        fmt.Println("err", err)
    }
}

输出:

Location: 
https://www.washingtonpost.com/news-sitemaps/politics.xml
resp <nil>
err parse 
https://www.washingtonpost.com/news-sitemaps/politics.xml
: first path segment in URL cannot contain colon
Location: 
https://www.washingtonpost.com/news-sitemaps/opinions.xml
resp <nil>
err parse 
https://www.washingtonpost.com/news-sitemaps/opinions.xml
: first path segment in URL cannot contain colon
...
...

我的猜测是 Location.Loc 在实际地址前后返回一个新行。例如:\n位置:https://www.washingtonpost.com/news-sitemaps/politics.xml\n

因为硬编码 URL 按预期工作:

for _, Location := range s.Locations {
        fmt.Printf("Location: %s", Location.Loc)
        test := "https://www.washingtonpost.com/news-sitemaps/politics.xml"
        resp, err := http.Get(test)
        fmt.Println("resp", resp)
        fmt.Println("err", err)
    }

输出，如您所见，错误为零:

Location: 
https://www.washingtonpost.com/news-sitemaps/politics.xml
resp &{200 OK 200 HTTP/2.0 2 0 map[Server:[nginx] Arc-Service:[api] Arc-Org-Name:[washpost] Expires:[Sat, 02 Feb 2019 05:32:38 GMT] Content-Security-Policy:[upgrade-insecure-requests] Arc-Deployment:[washpost] Arc-Organization:[washpost] Cache-Control:[private, max-age=60] Arc-Context:[index] Arc-Application:[Feeds] Vary:[Accept-Encoding] Content-Type:[text/xml; charset=utf-8] Arc-Servername:[api.washpost.arcpublishing.com] Arc-Environment:[index] Arc-Org-Env:[washpost] Arc-Route:[/feeds] Date:[Sat, 02 Feb 2019 05:31:38 GMT]] 0xc000112870 -1 [] false true map[] 0xc00017c200 0xc0000ca370}
err <nil>
Location: 
...
...

但我是 Go 的新手，所以我不知道哪里出了问题。你能告诉我哪里错了吗？

Answer 1

你是对的，问题出在换行符上。如您所见，您正在使用 Printf 而未添加任何 \n 并且在输出的开头添加了一个，在输出的结尾添加了一个。

您可以使用 strings.Trim删除那些换行符。这是 an example使用您要解析的站点地图。修剪字符串后，您将能够对其调用 http.Get 而不会出现任何错误。

func main() {
    var s SitemapIndex
    xml.Unmarshal(bytes, &s)

    for _, Location := range s.Locations {
        loc := strings.Trim(Location.Loc, "\n")
        fmt.Printf("Location: %s\n", loc)
    }
}

这段代码正确地输出了没有任何换行符的位置，正如预期的那样:

Location: https://www.washingtonpost.com/news-sitemaps/politics.xml
Location: https://www.washingtonpost.com/news-sitemaps/opinions.xml
Location: https://www.washingtonpost.com/news-sitemaps/local.xml
Location: https://www.washingtonpost.com/news-sitemaps/sports.xml
Location: https://www.washingtonpost.com/news-sitemaps/national.xml
Location: https://www.washingtonpost.com/news-sitemaps/world.xml
Location: https://www.washingtonpost.com/news-sitemaps/business.xml
Location: https://www.washingtonpost.com/news-sitemaps/technology.xml
Location: https://www.washingtonpost.com/news-sitemaps/lifestyle.xml
Location: https://www.washingtonpost.com/news-sitemaps/entertainment.xml
Location: https://www.washingtonpost.com/news-sitemaps/goingoutguide.xml

Location.Loc 字段中有这些换行符的原因是此 URL 返回的 XML。条目遵循以下形式:

<sitemap>
<loc>
https://www.washingtonpost.com/news-sitemaps/goingoutguide.xml
</loc>
</sitemap>

如您所见，loc 元素中的内容前后都有换行符。