xsl
<xsl:variable name="varName>
<xsl:value-of select="/can/be/a/long/path/down/xml/item[#id=1] />
</xsl:variable>
xml
<xml>
<item id="1" text="Yes">
<item id="2" text="No">
</xml>
use
I was thinking I could use like this:
<xsl:when test="$varName/#text = 'Yes'">
blah
</xsl:when>
but blank space is generated in place of variable. Is this even possible, have a node as a variable and use elsewhere?
<xsl:variable name="varName">
<xsl:value-of select="/can/be/a/long/path/down/xml/item[#id=1]" />
</xsl:variable>
This is one of the most common XSLT errors I see. Usually what people intended is:
<xsl:variable name="varName" select="/can/be/a/long/path/down/xml/item[#id=1]"/>
And most of the time, the code works just fine, except that it's a lot slower than it needs to be. But sometimes the fact that the two constructs are quite different beneath the covers comes back to bite you.
To understand the difference, xsl:variable with a select attribute binds the variable to whatever the select expression evaluates to, which in this case is a set of zero or more item elements. By contrast, xsl:variable with nested instructions creates a document node (XSLT 2.0) or result tree fragment (XSLT 1.0) whose content is a COPY of whatever those instructions produce. In this case, because the content is an xsl:value-of instruction, the variable contains a copy of the string-value of the selected node.
And of course, the string value of the selected node doesn't have any attributes, so test="$varname/#text = 'x'" will always return false.
Related
I wish to construct an XSL node set variable using a contained for-each loop. It is important that the constructed node set is the original (a selected) node set, not a copy.
Here is a much simplified version of my problem (which could of course be solved with a select, but that's not the point of the question). I've used the <name> node to test that the constructed node set variable is in fact in the original tree and not a copy.
XSL version 1.0, processor is msxsl.
Non-working XSL:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text" encoding="iso-8859-1" omit-xml-declaration="yes" />
<xsl:template match="/">
<xsl:variable name="entries">
<xsl:for-each select="//entry">
<xsl:copy-of select="."/>
</xsl:for-each>
</xsl:variable>
<xsl:variable name="entryNodes" select="msxsl:node-set($entries)"/>
<xsl:for-each select="$entryNodes">
<xsl:value-of select="/root/name"/>
<xsl:value-of select="."/>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
XML input:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<name>X</name>
<entry>1</entry>
<entry>2</entry>
</root>
Wanted output:
X1X2
Actual output:
12
Of course the (or a) problem is the copy-of, but I can't work out a way around this.
There isn't a "way around it" in XSLT 1.0 - it's exactly how this is supposed to work. When you have a variable that is declared with content rather than with a select then that content is a result tree fragment consisting of newly-created nodes (even if those nodes are a copy of nodes from the original tree). If you want to refer to the original nodes attached to the original tree then you must declare the variable using select. A better question would be to detail the actual problem and ask how you could write a suitable select expression to find the nodes you want without needing to use for-each - most uses of xsl:if or xsl:choose can be replaced with suitably constructed predicates, maybe involving judicious use of xsl:key, etc.
In XSLT 2.0 it's much more flexible. There's no distinction between node sets and result tree fragments, and the content of an xsl:variable is treated as a generic "sequence constructor" which can give you new nodes if you construct or copy them:
<xsl:variable name="example" as="node()*">
<xsl:copy-of select="//entry" />
</xsl:variable>
or the original nodes if you use xsl:sequence:
<xsl:variable name="example" as="node()*">
<xsl:sequence select="//entry" />
</xsl:variable>
I wish to construct an XSL node set variable using a contained
for-each loop.
I have no idea what that means.
It is important that the constructed node set is the original (a
selected) node set, not a copy.
This part I think I understand a little better. It seems you need to replace:
<xsl:variable name="entries">
<xsl:for-each select="//entry">
<xsl:copy-of select="."/>
</xsl:for-each>
</xsl:variable>
with:
<xsl:variable name="entries" select="//entry"/>
or, preferably:
<xsl:variable name="entries" select="root/entry"/>
The resulting variable is a node-set of the original entry nodes, so you can do simply:
<xsl:for-each select="$entries">
<xsl:value-of select="/root/name"/>
<xsl:value-of select="."/>
</xsl:for-each>
to get your expected result.
Of course, you could do the same thing by operating directly on the original nodes, in their original context - without requiring the variable.
In response to the comments you've made:
We obviously need a better example here, but I think I am getting a vague idea of where you want to go with this. But there are a few things you must understand first:
1.
In order to construct a variable which contains a node-set of nodes in their original context, you must use select. This does not place any limits whatsoever on what you can select. You can do your selection all at once, or in stages, or even in a loop (here I mean a real loop). You can combine the intermediate selections you have made in any way sets can be combined: union, intersection, or difference. But you must use select in all these steps, otherwise you will end up with a set of new nodes, no longer having the context they did in the source tree.
IOW, the only difference between using copy and select is that the former creates new nodes, which is precisely what you wish to avoid.
2.
xsl:for-each is not a loop. It has no hierarchy or chronology. All the nodes are processed in parallel, and there is no way to use the result of previous iteration in the current one - because no iteration is "previous" to another.
If you try to use xsl:for-each in order to add each of n processed nodes to a pre-existing node-set, you will end up with n results, each containing the pre-existing node-set joined with one of the processed nodes.
3.
I think you'll find the XPath language is quite powerful, and allows you to select the nodes you want without having to go through the complicated loops you hint at.
It might help if you showed us a problem that can't be trivially solved in XSLT 1.0. You can't solve your problem the way you are asking for: there is no equivalent of xsl:sequence in XSLT 1.0. But the problem you have shown us can be solved without such a construct. So please explain why you need what you are asking for.
More for reference than actual need: what is the XPath syntax to allow me to reference an element in a xsl:for-each block when the same element name is used elsewhere?
Please note, unfortunately this must be a 1.0 solution
For example, I have the following simple XML, and I want to match up the items with the same id value...
<data>
<block1>
<item><id>1</id><text>Hello</text></item>
<item><id>2</id><text>World</text></item>
</block1>
<block2>
<item><id>1</id><text>123</text></item>
<item><id>2</id><text>ABC</text></item>
</block2>
</data>
If I have a for-each on the block1, how can I reference both the id within the block1 and the id within the block2?
This will work, but I think it is messy...
<xsl:for-each select="//block1/item">
<xsl:variable name="id" select="id"/>
<xsl:value-of select="text"/> - <xsl:value-of select="//block2/item[id=$id]/text"/>
</xsl:for-each>
With the result of...
Hello - 123
World - ABC
Is there a simplified way of replacing the $id in select="//block2/item[id=$id]/text" so that it is referring to the id element from the for-each?
Another way to do it which you may find clearer, and will probably be faster, is to use keys:
<xsl:key name="b2" match="block2/item" use="id"/>
then
<xsl:value-of select="key('b2', id)/text"/>
What you have is correct and common as it is. There's no need to simplify it further; it's a standard idiom recognized and used by those working with XSLT.
I have an XML with 2 XML fragments, 1st one is a fragment where the new values must be applied (which can have pretty complex elements) like
... some static parents
<a:element1>
<a:subelement tag="someString">
<a:s1>a</a:s1>
</a:subelement>
</a:element1>
<a:element2>b</a:element2>
<a:element3>c</a:element3>
... lots of other elements like the above ones
and 2nd fragment that has XPaths generated from the first XML and a new value, like
<field>
<xpath>/Parent/element1/subelement[#tag="someString"]/s1</xpath>
<newValue>1</newValue>
</field>
<field>
<xpath>/Parent/element2</xpath>
<newValue>2</newValue>
</field>
We might not have new values to apply for all the elements in the first fragment.
I'm struggling to make an XSLT transformation that should apply the new values to the places indicated by the XPaths.
The output should be:
... some static parents
<a:element1>
<a:subelement tag="someString">
<a:s1>1</a:s1>
</a:subelement>
</a:element1>
<a:element2>2</a:element2>
... lots of other elements like the above ones
I have access to xalan:evaluate to evaluate the dynamic xpath. I'm trying different solutions, I will write them here when they will start to make sense.
Any ideas of approaches are well received. Thanks
Oki, I found out how, and I will write the answer here maybe someone sometime will need this:
<xsl:template match="/">
<!-- static parents -->
<a:Root>
<xsl:apply-templates select="/a:Root/a:Parent" />
</a:Root>
</xsl:template>
<xsl:template match="#*|*|text()">
<xsl:variable name="x" select="generate-id(../.)" />
<xsl:variable name="y" select="//field[generate-id(xalan:evaluate(xpath)) = $x]" />
<xsl:choose>
<xsl:when test="$y">
<xsl:value-of select="$y/newValue" />
</xsl:when>
<xsl:otherwise>
<xsl:copy>
<xsl:apply-templates select="#*|*|text()" />
</xsl:copy>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
And to explain the transformation:
I'm writing down part that is static and then call apply-templates on the fragment I'm interested in, that has a liquid structure.
Then I'm using a slightly modified identity transformation that copies everything from source to target (starting from the /a:Root/a:Parent fragment), except when we position ourselves on the text I'm interested in changing.
The text() I'm interested in will have as parent (../.) the element referred by an xpath string found in the second fragment. Variable x means, in the context of the when, this element.
Variable y finds a field element that has as child an xpath element that if evaluated using xalan will refer to the same element that the x variable relates to.
Now I used generate-id() in order to compare the physical elements, otherwise it would have compared by the toString of the element (which is wrong). If variable y doesn't exist, it means that I have no xpath element for this element that could have changed, and I'm leaving it alone. If the y variable exists, I can get from it the newValue and I'm currently positioned on the element which text I want to update.
I'm trying to map two documents witht the BizTalk Mapper and my target document should look like this:
<root>
<complexType>
<property>example</property>
</complexType>
<filler>
<padding>9999999</padding>
</filler>
<filler>
<padding>9999999</padding>
</filler>
<filler>
<padding>9999999</padding>
</filler>
</root>
The number of <filler> nodes that I should create is variable (from 0 to 9). It is basically the result of a calculation (based on some data provided in the source document).
Is there a way to create those <filler> nodes with some combination of functoids?
I tried to use the Table Looping functoid (created a table with only one column, the padding char '9') but doesn't really work because it creates as many <filler> nodes as rows are defined in the table, which is not what I want since the number of rows would have to be variable (again, based on a calculation).
What I currently do is pass the message (XmlDocument) to a C# method and then I programmatically append the <filler> nodes.
I'm hoping that there is a more "BizTalk-y" way of doing this with the Mapper.
I suspect that you will have to solve this problem by altering the XSLT.
Add some logic to create as many filler nodes as the result of your calculation dictates - you could create a template which you call in a loop perhaps, which would append a new filler section.
Hope this points you in the right direction.
As pointed out, XSLT can create nodes on the target document at will (I didn't know this and this was the key part).
Turns out that what I needed is a simple for-loop in XSLT. Once I realized this, a quick Google search yielded the following results:
http://quomon.com/question-How-to-make-a-for-loop-in-xslt-not-for-each-809.aspx
http://snippets.dzone.com/posts/show/930
Another thing worth noting is that (as pointed out by the first link), XSLT is a functional language, not procedural, so sometimes you do have to resort to using recursion or an extension.
This case is definitely one of those times since I couldn't use a careful selection of nodes using the select attribute on an xsl:for-each (since this filler data wasn't part of the source document).
Specifically, for this case, what I did was:
Add a Scripting functoid.
Add two inputs:
A constant with value "1" (this is the initial value of the i variable)
The length of the loop (number of times to repeat the body of the loop)
Paste the following XSLT template as an "Inline XSLT Call Template" script:
<xsl:template name="ForLoop">
<xsl:param name="i" /> <!-- index counter, 1-based, will be incremented with every recursive call -->
<xsl:param name="length" /> <!-- exit loop when i >= length -->
<!-- Output the desired node(s) if we're still looping -->
<!-- The base case is when i > length (in that case, do nothing) -->
<xsl:if test="$i <= $length">
<Filler>
<Padding>999999</Padding>
</Filler>
</xsl:if>
<!-- Call the ForLoop template recursively, incrementing i -->
<xsl:if test="$i <= $length">
<xsl:call-template name="ForLoop">
<xsl:with-param name="i">
<xsl:value-of select="$i + 1"/>
</xsl:with-param>
<xsl:with-param name="length">
<xsl:value-of select="$length"/>
</xsl:with-param>
</xsl:call-template>
</xsl:if>
</xsl:template>
Within an XSL sheet, I have a nodeset in a variable, $context.
How do I properly query an attribute of the topmost node in $context? Obviously, if $context was the current node, I would just write "#attname", but it is not. Currently I do $context/../#attname which is doesn't look great to me.
EDIT
Ok, the data.
Here is what I see in the VS.
In case you wonder how I got this strange thing: I UNION'ed a node with it's subnodes and an attribute selected out from a different node:
<xsl:with-param name="context" select=". | ../#res" />.
I'm not completely aware what results from this, but I can see that it works. Highlighted is the attribute I'm interested in.
Maybe that creates an attribute attached to nothing, if that makes sence at all :|
$context/../#attname
does not make too much sense. You can't go "up" here, as this would bring you "outside of" $context.
If the node-set contains something like this (a single node)
<node attname="foo">
<bar />
</node>
then:
$context/#attname
If it is like this (a list of nodes):
<node attname="foo">
<bar />
</node>
<node attname="foo">
<bar />
</node>
then:
$context[1]/#attname
All of this does not work if the variable contains a result tree fragment (RTF). In this case, you need to employ an extension function called node-set(). Most XSLT processors provide this function.
EDIT: Your variable holds a union of the current node and a naked attribute node from its parent:
<xsl:with-param name="context" select=". | ../#res" />
The result of a union will always be in document order, so even though you selected the attribute after the context node in the XPath, in the resulting node set it will come before - the parent of the context node is before the context node in document order.
You need $context[1] to grab the attribute node, and $context[2] to grab the other node.
I must say that this is some strange and probably unnecessary complicated use of variables. I'm sure there is a way to do this in a less painful fashion. For example you could do
<xsl:with-param name="context" select="." />
and then use $context/../#res in the called template. That would be a lot more straight-forward than what you are trying now.
Also, if the <xsl:with-param> you show here is part of an <xsl:call-template>, you can drop that param entirely. When a template is called (instead of applied), then the context node does not change, passing it in is redundant.
In addition to tomalak's answer if you ever do need to propagate back up to the root you could try:
ancestor::*[not(..)]
Would love to hear of a situation where you might want/need this though.
Try it yourself by pasting:
//pet/ancestor::*[not(..)]
in this online Xpath test tool.
As you have <xsl:with-param name="context" select=". | ../#res" /> the 'res' attribute is part of the node-set (XPath 1.0) or sequence (XPath 2.0) the variable named 'context' is bound to. With XPath 2.0 you could use $context/self::attribute(res) but XPath 1.0 has no comparable expression so what you have already ($context[1] or $context/../#res) is all you can do in my view.