XML::PatAct::ToObjects
XML::PatAct::ToObjectUser Contributed Perl DocumentaXML::PatAct::ToObjects(3)
NAME
XML::PatAct::ToObjects - An action module for creating Perl objects
SYNOPSIS
use XML::PatAct::ToObjects;
my $patterns = [ PATTERN => [ OPTIONS ],
PATTERN => "PERL-CODE",
... ];
my $matcher = XML::PatAct::ToObjects->new( Patterns => $patterns,
Matcher => $matcher,
CopyId => 1,
CopyAttributes => 1 );
DESCRIPTION
XML::PatAct::ToObjects is a PerlSAX handler for applying pattern-
action lists to XML parses or trees. XML::PatAct::ToObjects creates
Perl objects of the types and contents of the action items you define.
New XML::PatAct::ToObject instances are creating by calling ‘new()’.
Parameters can be passed as a list of key, value pairs or a hash.
‘new()’ requires the Patterns and Matcher parameters, the rest are
optional:
Patterns
The pattern-action list to apply.
Matcher
An instance of the pattern or query matching module.
CopyId
Causes the ‘ID’ attribute, if any, in a source XML element to be
copied to an ‘ID’ attribute in newly created objects. Note that
IDs may be lost of no pattern matches that element or an object is
not created ("-make") for that element.
CopyAttributes
Causes all attributes of the element to be copied to the newly
created objects.
Each action can either be a list of options defined below or a string
containing a fragment of Perl code. If the action is a string of Perl
code then simple then some simple substitutions are made as described
further below.
Options that can be used in an action item containing an option-list:
-holder
Ignore this element, but continue processing it’s children (com-
pare to -ignore). "-pcdata" may be used with this option.
-ignore
Ignore (discard) this element and it’s children (compare to
-holder).
-pcdata
Character data in this element should be copied to the "Contents"
field.
-make PACKAGE
Create an object blessed into PACKAGE, and continue processing
this element and it’s children. PACKAGE may be the type ‘"HASH"’
to simply create an anonyous hash.
-args ARGUMENTS
Use ARGUMENTS in creating the object specified by -make. This is
commonly used to copy element attributes into fields in the newly
created object. For example:
-make => ’HASH’, -args => ’URL => %{href}’
would copy the ‘"href"’ attribute in an element to the ‘"URL"’
field of the newly created hash.
-field FIELD
Store this element, object, or children of this element in the
parent object’s field named by FIELD.
-push-field FIELD
Similar to -field, except that FIELD is an array and the contents
are pushed onto that array.
-value VALUE
Use VALUE as a literal value to store in FIELD, otherwise ignoring
this element and it’s children. Only valid with -field or
-push-field. ‘"%{ATTRIBUTE}"’ notation can be used to substitute
the value of an attribute into the literal value.
-as-string
Convert the contents of this element to a string (as in
"XML::Grove::AsString") and store in FIELD. Only valid with
-field or -push-field.
-grove
Copy this element to FIELD without further processing. The ele-
ment can then be processed later as the Perl objects are manipu-
lated. Only valid with -field or -push-field. If ToObjects is
used with PerlSAX, this will use XML::Grove::Builder to build the
grove element.
-grove-contents
Used with -make, -grove-contents creates an object but then takes
all of the content of that element and stores it in Contents.
If an action item is a string, that string is treated as a fragment of
Perl code. The following simple substitutions are performed on the
fragment to provide easy access to the information being converted:
@ELEM@
The object that caused this action to be called. If ToObjects is
used with PerlSAX this will be a hash with the element name and
attributes, with XML::Grove this will be the element object, with
Data::Grove it will be the matching object, and with XML::DOM it
will be an XML::DOM::Element.
EXAMPLE
The example pattern-action list below will convert the following XML
representing a Database schema:
<schema>
<table>
<name>MyTable</name>
<summary>A short summary</summary>
<description>A long description that may
contain a subset of HTML</description>
<column>
<name>MyColumn1</name>
<summary>A short summary</summary>
<description>A long description</description>
<unique/>
<non-null/>
<default>42</default>
</column>
</table>
</schema>
into Perl objects looking like:
[
{ Name => "MyTable",
Summary => "A short summary",
Description => $grove_object,
Columns => [
{ Name => "MyColumn1",
Summary => "A short summary",
Description => $grove_object,
Unique => 1,
NonNull => 1,
Default => 42
}
]
}
]
Here is a Perl script and pattern-action list that will perform the
conversion using the simple name matching pattern module XML::Pat-
Act::MatchName. The script accepts a Schema XML file as an argument
($ARGV[0]) to the script. This script creates a grove as one of it’s
objects, so it requires the XML::Grove module.
use XML::Parser::PerlSAX;
use XML::PatAct::MatchName;
use XML::PatAct::ToObjects;
my $patterns = [
’schema’ => [ qw{ -holder } ],
’table’ => [ qw{ -make Schema::Table } ],
’name’ => [ qw{ -field Name -as-string } ],
’summary’ => [ qw{ -field Summary -as-string } ],
’description’ => [ qw{ -field Description -grove } ],
’column’ => [ qw{ -make Schema::Column -push-field Columns } ],
’unique’ => [ qw{ -field Unique -value 1 } ],
’non-null’ => [ qw{ -field NonNull -value 1 } ],
’default’ => [ qw{ -field Default -as-string } ],
];
my $matcher = XML::PatAct::MatchName->new( Patterns => $patterns );
my $handler = XML::PatAct::ToObjects->new( Patterns => $patterns,
Matcher => $matcher);
my $parser = XML::Parser::PerlSAX->new( Handler => $handler );
my $schema = $parser->parse(Source => { SystemId => $ARGV[0] } );
TODO
· It’d be nice if patterns could be applied even in -as-string and
-grove.
· Implement Perl code actions.
· -as-xml to write XML into the field.
AUTHOR
Ken MacLeod, ken@bitsko.slc.ut.us
SEE ALSO
perl(1), Data::Grove(3)
‘‘Using PatAct Modules’’ and ‘‘Creating PatAct Modules’’ in
libxml-perl.
perl v5.8.5 2000-02-22 XML::PatAct::ToObjects(3)
