如何让golang区分带有命名空间和不带命名空间的XML元素？

huangapple
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英文:

How to let golang distinguish XML elements with and without namespaces?

问题

假设我有以下的XML数据：

  1. <image> 
  2.   <url>http://sampleUrl.com</url>
  3. </image>
  5. <itunes:image url="http://sampleItunesUrl.com" />  //xmlData

我使用以下结构体对其进行解码：

  1. type Response struct {
  2.    XMLName   xml.Name   `xml:"resp"`
  3.    Image []struct {
  4.         URL string   `xml:"url"`
  5.   } `xml:"image"`
  6.   ItunesImage  struct {
  7.        URL string `xml:"url,attr"`
  8.   }  `xml:"http://www.itunes.com/dtds/podcast-1.0.dtd image"`
  10. }

我有如下代码：

  1. var resp Response 
  2. err := xml.Unmarshal([]byte(xmlData), &resp)
  3. if err != nil {
  4. 	fmt.Printf("Error decoding XML: %s\n", err)
  5. 	return
  6. }
  7. for _, img := range resp.Image{
  8.     if img.URL != "" {
  9.         //<image>，而不是<itunes:image>
  10.     }
  11. }

来处理解码。

我遇到的问题是，Image []struct似乎将<image>和<itunes:image>都视为<image>元素，因为它们都有"image"。为了过滤掉<itunes:image>，我使用的方法是让Image []struct中的每个元素检查它们的url是否为空字符串（因为对于<itunes:image>，它的url是属性）。

另一种方法是编写自己的Unmarshal函数来区分带有和不带有itunes命名空间的XML元素。基本上，我希望Image []struct只包含<image>元素。

我想知道Go语言是否有一些内置的功能可以区分它们？还是我必须编写代码来过滤掉<itunes:image>？

英文:

suppose I have the following XML data:

  1. &lt;image&gt; 
  2.   &lt;url&gt; http://sampleUrl.com
  3.   &lt;/url&gt;
  4. &lt;/image&gt;
  6. &lt;itunes:image url=&quot;http://sampleItunesUrl.com&quot; /&gt;  //xmlData

I use this struct to decode it:

  1. type Response struct {
  2.    XMLName   xml.Name   `xml:&quot;resp&quot;`
  3.    Image []struct {
  4.         URL string   `xml:&quot;url&quot;`
  5.   } `xml:&quot;image&quot;`
  6.   ItunesImage  struct {
  7.        URL string `xml:&quot;url,attr&quot;`
  8.   }  `xml:&quot;http://www.itunes.com/dtds/podcast-1.0.dtd image&quot;`
  10. }

and I have codes like:

  1. var resp Response 
  2. err := xml.Unmarshal([]byte(xmlData), &amp;resp)
  3. if err != nil {
  4. 	fmt.Printf(&quot;Error decoding XML: %s\n&quot;, err)
  5. 	return
  6. }
  7. for _, img := range resp.Image{
  8.     if img.URL != &quot;&quot; {
  9.         //&lt;image&gt;, not &lt;itunes:image&gt;
  10.     }
  11. }

to process decoding

The problem I am having is that looks like Image []struct considers both &lt;image&gt; and &lt;itunes:image to be &lt;image&gt; element, since they both have "image". To filter out &lt;itunes:image, the approach I am using is to let each one in Image []struct examine if their url are empty strings (because for &lt;itunes:image its url is attribute).

Another approach is to write my own Unmarshal function to distinguish between XML elements with and without itunes namespace. Basically I want Image []struct to only hold elements &lt;image&gt;

I am wondering if go has some built-in functionalities to distinguish? Or I have to write my codes to filter out &lt;itunes:image&gt; ?

答案1

得分: 2

请注意，字段的顺序很重要。ItunesImage具有更具体的标签，因此应该在Image之前。

  1. package main
  3. import (
  4. 	"encoding/xml"
  5. 	"fmt"
  6. )
  8. func main() {
  9. 	type Response struct {
  10. 		XMLName     xml.Name `xml:"resp"`
  11. 		ItunesImage struct {
  12. 			URL string `xml:"url,attr"`
  13. 		} `xml:"http://www.itunes.com/dtds/podcast-1.0.dtd image"`
  14. 		Image []struct {
  15. 			URL string `xml:"url"`
  16. 		} `xml:"image"`
  17. 	}
  19. 	xmlData := `
  20. <resp xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd">
  21.   <image>
  22.     <url>http://sampleUrl.com</url>
  23.   </image>
  24.   <itunes:image url="http://sampleItunesUrl.com/" />
  25. </resp>
  26. `
  28. 	var resp Response
  29. 	err := xml.Unmarshal([]byte(xmlData), &resp)
  30. 	if err != nil {
  31. 		fmt.Printf("解码XML时出错：%s\n", err)
  32. 		return
  33. 	}
  34. 	fmt.Printf("ItunesImage：%v\n", resp.ItunesImage)
  35. 	fmt.Printf("Images：%v\n", resp.Image)
  36. }

如果你只需要从<image>标签中获取image/url，你可以像这样定义Response结构体：

  1. type Response struct {
  2. 	XMLName xml.Name `xml:"resp"`
  3. 	Image   []string `xml:"image>url"`
  4. }

关于标题中的一般问题（如何让golang区分带有命名空间和不带命名空间的XML元素），你可以使用名为XMLName的字段捕获元素名称，并检查该字段的Space成员。请参考下面的示例：

  1. package main
  3. import (
  4. 	"encoding/xml"
  5. 	"fmt"
  6. )
  8. func main() {
  9. 	type Response struct {
  10. 		XMLName xml.Name `xml:"resp"`
  11. 		Image   []struct {
  12. 			XMLName xml.Name
  13. 			URL     string `xml:"url"`
  14. 		} `xml:"image"`
  15. 	}
  17. 	xmlData := `
  18. <resp xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd">
  19.   <image>
  20.     <url>http://sampleUrl.com</url>
  21.   </image>
  22.   <itunes:image>
  23.     <url>http://sampleItunesUrl.com/</url>
  24.   </itunes:image>
  25. </resp>
  26. `
  28. 	var resp Response
  29. 	err := xml.Unmarshal([]byte(xmlData), &resp)
  30. 	if err != nil {
  31. 		fmt.Printf("解码XML时出错：%s\n", err)
  32. 		return
  33. 	}
  34. 	for _, img := range resp.Image {
  35. 		fmt.Printf("命名空间：%q, URL：%s\n", img.XMLName.Space, img.URL)
  36. 	}
  37. }

上述示例的输出结果为：

  1. 命名空间："", URL：http://sampleUrl.com
  2. 命名空间："http://www.itunes.com/dtds/podcast-1.0.dtd", URL：http://sampleItunesUrl.com/
英文:

Please note that the field order matters. ItunesImage has a more specific tag, so it should go before Image.

  1. package main
  3. import (
  4. 	&quot;encoding/xml&quot;
  5. 	&quot;fmt&quot;
  6. )
  8. func main() {
  9. 	type Response struct {
  10. 		XMLName     xml.Name `xml:&quot;resp&quot;`
  11. 		ItunesImage struct {
  12. 			URL string `xml:&quot;url,attr&quot;`
  13. 		} `xml:&quot;http://www.itunes.com/dtds/podcast-1.0.dtd image&quot;`
  14. 		Image []struct {
  15. 			URL string `xml:&quot;url&quot;`
  16. 		} `xml:&quot;image&quot;`
  17. 	}
  19. 	xmlData := `
  20. &lt;resp xmlns:itunes=&quot;http://www.itunes.com/dtds/podcast-1.0.dtd&quot;&gt;
  21.   &lt;image&gt;
  22.     &lt;url&gt;http://sampleUrl.com&lt;/url&gt;
  23.   &lt;/image&gt;
  24.   &lt;itunes:image url=&quot;http://sampleItunesUrl.com/&quot; /&gt;
  25. &lt;/resp&gt;
  26. `
  28. 	var resp Response
  29. 	err := xml.Unmarshal([]byte(xmlData), &amp;resp)
  30. 	if err != nil {
  31. 		fmt.Printf(&quot;Error decoding XML: %s\n&quot;, err)
  32. 		return
  33. 	}
  34. 	fmt.Printf(&quot;ItunesImage: %v\n&quot;, resp.ItunesImage)
  35. 	fmt.Printf(&quot;Images: %v\n&quot;, resp.Image)
  36. }

And if you only need image/url from the &lt;image&gt; tag, you could define the Response struct like this:

  1. type Response struct {
  2. 	XMLName xml.Name `xml:&quot;resp&quot;`
  3. 	Image   []string `xml:&quot;image&gt;url&quot;`
  4. }

Regarding the general question in the title (How to let golang distinguish XML elements with and without namespaces?), you can capture the element name with a field named XMLName and examine the Space member of this field. See the demo below:

  1. package main
  3. import (
  4. 	&quot;encoding/xml&quot;
  5. 	&quot;fmt&quot;
  6. )
  8. func main() {
  9. 	type Response struct {
  10. 		XMLName xml.Name `xml:&quot;resp&quot;`
  11. 		Image   []struct {
  12. 			XMLName xml.Name
  13. 			URL     string `xml:&quot;url&quot;`
  14. 		} `xml:&quot;image&quot;`
  15. 	}
  17. 	xmlData := `
  18. &lt;resp xmlns:itunes=&quot;http://www.itunes.com/dtds/podcast-1.0.dtd&quot;&gt;
  19.   &lt;image&gt;
  20.     &lt;url&gt;http://sampleUrl.com&lt;/url&gt;
  21.   &lt;/image&gt;
  22.   &lt;itunes:image&gt;
  23.     &lt;url&gt;http://sampleItunesUrl.com/&lt;/url&gt;
  24.   &lt;/itunes:image&gt;
  25. &lt;/resp&gt;
  26. `
  28. 	var resp Response
  29. 	err := xml.Unmarshal([]byte(xmlData), &amp;resp)
  30. 	if err != nil {
  31. 		fmt.Printf(&quot;Error decoding XML: %s\n&quot;, err)
  32. 		return
  33. 	}
  34. 	for _, img := range resp.Image {
  35. 		fmt.Printf(&quot;namespace: %q, url: %s\n&quot;, img.XMLName.Space, img.URL)
  36. 	}
  37. }

The output of the above demo is:

  1. namespace: &quot;&quot;, url: http://sampleUrl.com
  2. namespace: &quot;http://www.itunes.com/dtds/podcast-1.0.dtd&quot;, url: http://sampleItunesUrl.com/

huangapple
  • 本文由 发表于 2023年4月1日 06:39:25
  • 转载请务必保留本文链接：https://go.coder-hub.com/75903249.html
  • go
  • xml
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