XML解析返回帶換行符的字符串

Question

我試圖通過站點地圖解析XML，然后遍歷該地址以獲取Go中帖子的詳細信息。 但是我收到這個奇怪的錯誤：

：URL中的第一個路徑段不能包含冒號

這是代碼片段：

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)
    }
}

並輸出：

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
...
...

我的猜測是Location.Loc在實際地址之前和之后返回新行。 例如： \\nLocation: https://www.washingtonpost.com/news-sitemaps/politics.xml\\n : \\nLocation: https://www.washingtonpost.com/news-sitemaps/politics.xml\\n

由於對URL進行硬編碼可以按預期工作：

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)
    }

如您所見，輸出為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: 
...
...

但是我對Go還是很陌生，所以我不知道出了什么問題。 你能告訴我我哪里錯了嗎？

Answer 1

確實您是對的，問題出在換行符上。 如您所見，您正在使用Printf而不添加任何\\n並且在輸出的開始處添加一個，在結尾處添加一個。

您可以使用strings.Trim刪除這些換行符。 這是使用您要解析的站點地圖的示例 。 字符串被修剪后，您將可以調用http.Get ，而不會發生任何錯誤。

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)
    }
}

此代碼正確輸出了沒有換行符的位置，如預期的那樣：

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

之所以在Location.Loc字段中包含這些換行符，是因為此URL返回了XML。 條目采用以下形式：

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

如您所見， loc元素中的內容前后都有換行符。

Answer 2

請參閱修改后的代碼中嵌入的注釋，以描述和解決此問題

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 {
            // Note that %v shows that there are indeed newlines at beginning and end of Location.Loc
            fmt.Printf("Location: (%v)", Location.Loc)
            // solution: use strings.TrimSpace to remove newlines from Location.Loc
            resp, err := http.Get(strings.TrimSpace(Location.Loc))
            fmt.Println("resp", resp)
            fmt.Println("err", err)
    }

}