Xpath add a field from an item to another item with a reference id - xpath

Question

This is the structure of the file I need to import.
<channel>
<item>
<type>image</type>
<title>title image</title>
<id>1</id>
<image_url>url_to_image</image_url>
</item>
<item>
<type>page</type>
<title>node title</title>
<id>2</id>
<ref>
<entity>image_ref</entity>
<ref_value>1</ref_value>
</ref>
<ref>
<entity>category</entity>
<ref_value>5</ref_value>
</ref>
</item>
</channel>
In the page item the tag contains the id of the image item.
How do I add the image url from the image item to the page item?
I'm trying to use
/channel/item[id=ref/ref_value[../entity/text() = 'image_ref']]/image_url but it does not work...
What's the XPath expression to not import the image item but just the page item?
Thanks in advance

Answer 1

Use:
/*/item[type='image' and id=../item[type='page']
/ref[entity = 'image_ref']/ref_value]
/image_url/text()
XSLT - based verification:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match="/">
<xsl:copy-of select=
"/*/item[type='image' and id=../item[type='page']
/ref[entity = 'image_ref']/ref_value]
/image_url/text()"/>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied to the provided XML document:
<channel>
<item>
<type>image</type>
<title>title image</title>
<id>1</id>
<image_url>url_to_image</image_url>
</item>
<item>
<type>page</type>
<title>node title</title>
<id>2</id>
<ref>
<entity>image_ref</entity>
<ref_value>1</ref_value>
</ref>
<ref>
<entity>category</entity>
<ref_value>5</ref_value>
</ref>
</item>
</channel>
the XPath expression is evaluated and the result of this evaluation is copied to the output:
url_to_image
Update:
The OP has implied in comments that there may be many "page items" and "image items" and that he needs an expression, getting the image url for only a specific page.
This XPath expression:
/*/item[type='image'
and id=../item[type='page'][1]
/ref[entity = 'image_ref']/ref_value
]
/image_url/text()"/>
produces the wanted image url for the first "page item" in the following XML document:
<channel>
<item>
<type>image</type>
<title>title image</title>
<id>1</id>
<image_url>url_to_image</image_url>
</item>
<item>
<type>image</type>
<title>title image</title>
<id>2</id>
<image_url>url2_to_image</image_url>
</item>
<item>
<type>page</type>
<title>node title</title>
<id>3</id>
<ref>
<entity>image_ref</entity>
<ref_value>1</ref_value>
</ref>
<ref>
<entity>category</entity>
<ref_value>5</ref_value>
</ref>
</item>
<item>
<type>page</type>
<title>node title</title>
<id>4</id>
<ref>
<entity>image_ref</entity>
<ref_value>2</ref_value>
</ref>
<ref>
<entity>category</entity>
<ref_value>5</ref_value>
</ref>
</item>
</channel>
The result produced is:
url_to_image
To get the wanted url for the second page item, we simply modify the above XPath expression to:
/*/item[type='image'
and id=../item[type='page'][2]
/ref[entity = 'image_ref']/ref_value
]
/image_url/text()"/>
and now the result is:
url2_to_image