[PLEASE READ] XPath query help

[gfrommer]

Hello everyone,

I've been reading through a bunch of XPath tutorials and am
confused by a couple items. First, is it possible to have multiple
predicates in my XPath statement. For example, the following xpath
statement: "//AAA/BBB[@name="b1"]/c[c=6]" should only return the last
<c> node containing the 6, correct? Also consider the statement
"//AAA/BBB[@name="b1" or @name="b2"]" returns the first two <BBB>
items, correct? the and's and or's in the predicates are all right yes?

Does JAXEN support these kind of queries?

<AAA>
<BBB name = "b1">
<c>4</c>
</BBB>
<BBB name = "b2">
<c>5</c>
</BBB>
<BBB name = "b1">
<c>6</c>
</BBB>
</AAA>


Also, I read that the "|" operator will combine the results of several
xpath queries. I understand that it will append the results into one
big list... Is there any way to preform logical AND's OR's and NOT's on
the results of each query and have it combine into one big list?
(Instead of a simple append)

Thanks everyone

 

[Joris Gillis]

Hi,

I've been reading through a bunch of XPath tutorials and am
confused by a couple items. First, is it possible to have multiple
predicates in my XPath statement. AFAIK, perfectly possible
For example, the following xpath
statement: "//AAA/BBB[@name="b1"]/c[c=6]" should only return the last
<c> node containing the 6, correct?

Also consider the statement
"//AAA/BBB[@name="b1" or @name="b2"]" returns the first two <BBB>
items, correct? the and's and or's in the predicates are all right yes?

Yes, (but mind the quotes)

Does JAXEN support these kind of queries?

I have no idea.

<AAA>
<BBB name = "b1">
<c>4</c>
</BBB>
<BBB name = "b2">
<c>5</c>
</BBB>
<BBB name = "b1"> Is suppose that should be 'b3'
<c>6</c>
</BBB>
</AAA>


Also, I read that the "|" operator will combine the results of several
xpath queries. I understand that it will append the results into one
big list... Is there any way to preform logical AND's OR's and NOT's on
the results of each query and have it combine into one big list?
(Instead of a simple append)

Only if you use XPath2.0 or extension functions.

regards,

 

[David Carlisle]

Also, I read that the "|" operator will combine the results of several
xpath queries. I understand that it will append the results into one
big list... Is there any way to preform logical AND's OR's and NOT's on
the results of each query and have it combine into one big list?
(Instead of a simple append)


No, XPath 1 doesn't have lists, only sets (which are unordered) and | is
set-union not append, so if $a is a variable holding a node then $a | $a
is just one copy of the node in $a, not two. so | is not at all like a
list append.

David

 

[gfrommer]

Also, I read that the "|" operator will combine the results of several
xpath queries. I understand that it will append the results into one
big list... Is there any way to preform logical AND's OR's and NOT's on
the results of each query and have it combine into one big list?
(Instead of a simple append)


No, XPath 1 doesn't have lists, only sets (which are unordered) and | is
set-union not append, so if $a is a variable holding a node then $a | $a
is just one copy of the node in $a, not two. so | is not at all like a
list append.

David

The set-union that you are talking about... is that the equivilent of a
logical AND between those two sets?

Thanks

 

[David Carlisle]

David Carlisle wrote:

The set-union that you are talking about... is that the equivilent of a
logical AND between those two sets?

Thanks

Not sure what you mean. There are some basic operations that apply to
sets, union and intersection being the main ones. Logical operations
don't naturally apply to sets. There are of course various ways to map
logical operations into set ones, union can be read as and or or
depending on the circumstances.

<xsl:template match="foo|bar">

that template matches any element that is foo OR bar
or you could say
that template matches foo elements AND bar elements

David