XML解析返回带换行符的字符串

Question

I am trying to parse XML via the sitemap, and then loop over the address to get the details of the post in Go. But I am getting this weird error:

: first path segment in URL cannot contain colon

This is the code snippet:

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)
    }
}

And the output:

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
...
...

My guess is that the Location.Loc returns a new line before and after the actuall address. Eg: Location: https://www.washingtonpost.com/news-sitemaps/politics.xml

Because hardcoding the URL works as expected:

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)
    }

Output, as you can see the error is nil:

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: 
...
...

But I am very new to Go, and so I have no idea what's wrong. Could you please tell me where I am wrong?

Answer 1

You are right indeed, the issue comes from the newlines. As you can see, you are using Printf without adding any and one is added at the beginning and one at the end in the output.

You can use strings.Trim to remove those newlines. Here is an example working with the sitemap that you are trying to parse. Once the string is trimmed, you will be able to call http.Get on it without any errors.

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

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

This code properly outputs the locations without any newlines, as expected:

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

The reason why you have those newlines in the Location.Loc field is because of the XML returned by this URL. Entries are following this form:

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

And as you can see, there are newlines before and after the content within the loc elements.