SimpleTaglib(3)
NAME
Apache::AxKit::XSP::Language::SimpleTaglib - alternate XSP taglib
helper
SYNOPSIS
package Your::XSP::Package;
use Apache::AxKit::Language::XSP::SimpleTaglib;
... more initialization stuff, start_document handler, utility functions, whatever
you like, but no parse_start/end handler needed - if in doubt, just leave empty ...
package Your::XSP::Package::Handlers;
sub some_tag : attrib(id) attribOrChild(some-param) node(result) keepWhitespace {
my ($e, $tag, %attr) = @_;
return 'do_something($attr_some_param,'.$attr{'id'}.');';
}
DESCRIPTION
This taglib helper allows you to easily write tag handlers with most of
the common behaviours needed. It manages all 'Design Patterns' from the
XSP man page plus several other useful tag styles.
Simple handler subs
A tag "<yourNS:foo>" will trigger a call to sub "foo" during the clos-
ing tag event. What happens in between can be configured in many ways
using function attributes. In the rare cases where some action has to
happen during the opening tag event, you may provide a sub "foo__open"
(double underscore) which will be called at the appropriate time. Usu-
ally you would only do that for 'if'- style tags which enclose some
block of code.
Context sensitive handler subs
A sub named "foo___bar" (triple underscore) gets called on the follow-
ing XML input: "<yourNS:foo><yourNS:bar/></yourNS:foo>". Handler subs
may have any nesting depth. The rule for opening tag handlers applies
here as well. The sub name must represent the exact tag hierarchy
(within your namespace).
Names, parameters, return values
Names for subs and variables get created by replacing any non-alphanu-
meric character in the original tag or attribute to underscores. For
example, 'get-id' becomes 'get_id'.
The called subs get passed 3 parameters: The parser object, the tag
name, and an attribute hash. This hash only contains XML attributes
declared using the 'attrib()' function attribute. (Try not to confuse
these two meanings of 'attribute' - unfortunately XML and Perl both
call them that way.) All other declared parameters get converted into
local variables with prefix 'attr_'.
If a sub has any result attribute ('node', 'expr', etc.), it gets
called in list context. If neccessary, returned lists get converted to
scalars by joining them without separation. Plain subs (without result
attribute) inherit their context and have their return value left
unmodified.
Precedence
If more than one handler matches a tag, the following rules determine
which one is chosen. Remember, though, that only tags in your names-
pace are considered.
1. If the innermost tag has a 'childStruct' spec which matches, the
internal childStruct handler takes precedence.
2. Otherwise, if any surrounding tag has a matching 'child' or 'attri-
bOrChild' attribute, the internal handler for the innermost matching
tag gets chosen.
3. Otherwise, the handler sub with the deepest tag hierarchy gets
called.
Utility functions
Apache::AxKit::Language::XSP contains a few handy utility subs:
o start_elem, end_elem, start_attr, end_attr - these create elements
and attributes in the output document. Call them just like you call
start_expr and end_expr.
o makeSingleQuoted - given a scalar as input, it returns a scalar which
yields the exact input value when evaluated; handy when using unknown
text as-is in return values.
o makeVariableName - creates a valid, readable perl identifier from
arbitrary input text. The return values might overlap.
Available attributes
Parameters to attributes get handled as if 'q()' enclosed them. Commas
separate arguments, so values cannot contain commas.
Result attributes
Choose none or one of these to select output behaviour.
"expr"
Makes this tag behave like an '<xsp:expr>' tag, creating text nodes or
inline text as appropriate. Choose this if you create plain text which
may be used everywhere, including inside code. This attribute has no
parameters.
"node(name)"
Makes this tag create an XML node named "name". The tag encloses all
content as well as the results of the handler sub. Choose this if you
want to create one XML node with all your output.
"nodelist(name)"
Makes this tag create a list of XML nodes named "name". The tag(s) do
not enclose content nodes, which become preceding siblings of the gen-
erated nodes. The return value gets converted to a node list by enclos-
ing each element with an XML node named "name". Choose this if you
want to create a list of uniform XML nodes with all your output.
"exprOrNode(name,attrname,attrvalue)"
Makes this tag behave described under either 'node()' or 'expr',
depending on the value of XML attribute "attrname". If that value
matches "attrvalue", it will work like 'node()', otherwise it will work
like 'expr'. "attrname" defaults to 'as', "attrvalue" defaults to
'node', thus leaving out both parameters means that 'as="node"' will
select 'node()' behaviour. Choose this if you want to let the XSP
author decide what to generate.
"exprOrNodelist(name,attrname,attrvalue)"
Like exprOrNode, selecting between 'expr' and 'nodelist()' behaviour.
"struct"
Makes this tag create a more complex XML fragment. You may return a
single hashref or an array of hashrefs, which get converted into an XML
structure. Each hash element may contain a scalar, which gets converted
into an XML tag with the key as name and the value as content. Alterna-
tively, an element may contain an arrayref, which means that an XML tag
encloses each single array element. Finally, you may use hashrefs in
place of scalars to create substructures. To create attributes on tags,
use a hashref that contain the attribute names prefixed by '@'. A ''
(empty string) as key denotes the text contents of that node.
In an expression context, passes on the unmodified return value.
Other output attributes
These may appear more than once and modify output behaviour.
"nodeAttr(name,expr,...)"
Adds an XML attribute named "name" to all generated nodes. "expr" gets
evaluated at run time. Evaluation happens once for each generated
node. Of course, this tag only makes sense with 'node()' type handlers.
Input attributes
These tags specify how input gets handled. Most may appear more than
once, if that makes sense.
"attrib(name,...)"
Declares "name" as a (non-mandatory) XML attribute. All attributes
declared this way get passed to the handler subs in the attribute hash.
"child(name,...)"
Declares a child tag "name". It always lies within the same namespace
as the taglib itself. The contents of the tag, if any, get saved in a
local variable named $attr_"name". If the child tag appears more than
once, the last value overrides any previous value.
"attribOrChild(name,...)"
Declares an attribute or child tag named "name". A variable is created
just like for 'child()', containing the attribute or child tag con-
tents. If both appear, the contents of the child tag take precedence.
"keepWhitespace"
Makes this tag preserve contained whitespace.
"captureContent"
Makes this tag store the enclosed content in '$_' for later retrieval
in the handler sub, instead of adding it to the enclosing element. Non-
text nodes will not work as expected.
"childStruct(spec)"
Marks this tag to take a complex xml fragment as input. The resulting
data structure is available as %_ in the sub. Whitespace is always pre-
served.
"spec" has the following syntax:
1. A "spec" consists of a list of tag names, separated by whitespace.
2. Tags may appear in any order.
3. A tag name prefixed by '@' may appear more than once in the xml doc-
ument. A tag name prefixed by '$' or without any prefix may only appear
once.
4. If a '{' follows a tag name, that tag has child tags. A valid "spec"
and a closing '}' must follow.
5. A tag name prefixed by '*' does not indicate an input tag but speci-
fies the name for the text contents of the surrounding tag in the
resulting data structure. Such a tag name may not bear a '{...}' block.
6. Any tag without child tags may also appear as attribute of the par-
ent tag.
7. A tag name folloewd by one or more parameter specs in parentheses
means a hash gets created with the value of the corresponding attribute
(or child tag) as key. This usage does not forbid appending a '{...}'
block, which would result in a nested hash.
8. A tag name prefixed by '&' denotes a recursive structure. The tag
name must appear as the name of one of the surrounding '{...}'-blocks.
The innermost matching block gets chosen.
Example:
sub:
set_permission : childStruct(add{@permission{$type *name} $target $comment(lang)(day)} remove{@permission{$type *name} $target})
XML:
<set-permission>
<add>
<permission type="user">
foo
</permission>
<permission>
<type>group</type>
bar
</permission>
<target>/test.html</target>
<comment lang="en" day="Sun">Test entry</comment>
<comment lang="en" day="Wed">Test entry 2</comment>
<comment><lang>de</lang>Testeintrag</comment>
</add>
<remove target="/test2.html">
<permission type="user">
baz
</permission>
</remove>
</set-permission>
Result: a call to set_permission with %_ set like this:
%_ = (
add => {
permission => [
{ type => "user", name => 'foo' },
{ type => "group", name => 'bar' },
],
target => '/test.html',
comment => {
'en' => { 'Sun' => 'Test entry', 'Wed' => 'Test entry 2' },
'de' => { '' => 'Testeintrag' },
}
},
remove => {
permission => [
{ type => "user", name => 'baz' },
],
target => '/test2.html',
},
);
EXAMPLE
See AxKit::XSP::Sessions and AxKit::XSP::Auth source code for full-fea-
tured examples.
BUGS
Because of the use of perl attributes, SimpleTaglib will only work with
Perl 5.6.0 or later. This software is already tested quite well and
works for a number of simple and complex taglibs. Still, you may have
to experiment with the attribute declarations, as the differences can
be quite subtle but decide between 'it works' and 'it doesn't'. XSP can
be quite fragile if you start using heavy trickery.
If some tags don't work as expected, try surrounding the offending tag
with <xsp:content>, this is a common gotcha (but correct and intended).
If you find yourself needing <xsp:expr> around a tag, please contact
the author, as that is probably a bug.
AUTHOR
Jrg Walter <jwalt@cpan.org>
COPYRIGHT
Copyright (c) 2002 Jrg Walter. Documentation All rights reserved. This
program is free software; you can redistribute it and/or modify it
under the same terms as AxKit itself.
SEE ALSO
AxKit, Apache::AxKit::Language::XSP, Apache::AxKit::Lan-
guage::XSP::TaglibHelper
perl v5.8.0 Apache::AxKit::Language::XSP::SimpleTaglib(3)
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