Provided by: libxml-compile-perl_1.42-1_all 
NAME
XML::Compile::Schema - Compile a schema into CODE
INHERITANCE
XML::Compile::Schema
is a XML::Compile
XML::Compile::Schema is extended by
XML::Compile::Cache
SYNOPSIS
# compile tree yourself
my $parser = XML::LibXML->new;
my $tree = $parser->parse...(...);
my $schema = XML::Compile::Schema->new($tree);
# get schema from string
my $schema = XML::Compile::Schema->new($xml_string);
# get schema from file (most used)
my $schema = XML::Compile::Schema->new($filename);
my $schema = XML::Compile::Schema->new([glob "*.xsd"]);
# the "::Cache" extension has more power
my $schema = XML::Compile::Cache->new(\@xsdfiles);
# adding more schemas, from parsed XML
$schema->addSchemas($tree);
# adding more schemas from files
# three times the same: well-known url, filename in schemadir, url
# Just as example: usually not needed.
$schema->importDefinitions('http://www.w3.org/2001/XMLSchema');
$schema->importDefinitions('2001-XMLSchema.xsd');
$schema->importDefinitions(SCHEMA2001); # from ::Util
# alternatively
my @specs = ('one.xsd', 'two.xsd', $schema_as_string);
my $schema = XML::Compile::Schema->new(\@specs); # ARRAY!
# see what types are defined
$schema->printIndex;
# create and use a reader
use XML::Compile::Util qw/pack_type/;
my $elem = pack_type 'my-namespace', 'my-local-name';
# $elem eq "{my-namespace}my-local-name"
my $read = $schema->compile(READER => $elem);
my $data = $read->($xmlnode);
my $data = $read->("filename.xml");
# when you do not know the element type beforehand
use XML::Compile::Util qw/type_of_node/;
my $elem = type_of_node $xml->documentElement;
my $reader = $reader_cache{$type} # either exists
||= $schema->compile(READER => $elem); # or create
my $data = $reader->($xmlmsg);
# create and use a writer
my $doc = XML::LibXML::Document->new('1.0', 'UTF-8');
my $write = $schema->compile(WRITER => '{myns}mytype');
my $xml = $write->($doc, $hash);
$doc->setDocumentElement($xml);
# show result
print $doc->toString(1);
# to create the type nicely
use XML::Compile::Util qw/pack_type/;
my $type = pack_type 'myns', 'mytype';
print $type; # shows {myns}mytype
# using a compiled routines cache
use XML::Compile::Cache; # separate distribution
my $schema = XML::Compile::Cache->new(...);
# Show which data-structure is expected
print $schema->template(PERL => $type);
# Error handling tricks with Log::Report
use Log::Report mode => 'DEBUG'; # enable debugging
dispatcher SYSLOG => 'syslog'; # errors to syslog as well
try { $reader->($data) }; # catch errors in $@
DESCRIPTION
This module collects knowledge about one or more schemas. The most important method
provided is compile(), which can create XML file readers and writers based on the schema
information and some selected element or attribute type.
Various implementations use the translator, and more can be added later:
"$schema->compile('READER'...)" translates XML to HASH
The XML reader produces a HASH from a XML::LibXML::Node tree or an XML string. Those
represent the input data. The values are checked. An error produced when a value or
the data-structure is not according to the specs.
The CODE reference which is returned can be called with anything accepted by
dataToXML().
Example: create an XML reader
my $msgin = $rules->compile(READER => '{myns}mytype');
# or ... = $rules->compile(READER => pack_type('myns', 'mytype'));
my $xml = $parser->parse("some-xml.xml");
my $hash = $msgin->($xml);
or
my $hash = $msgin->('some-xml.xml');
my $hash = $msgin->($xml_string);
my $hash = $msgin->($xml_node);
"$schema->compile('WRITER', ...)" translates HASH to XML
The writer produces schema compliant XML, based on a Perl HASH. To get the data
encoding correctly, you are required to pass a document object in which the XML nodes
may get a place later.
Create an XML writer
my $doc = XML::LibXML::Document->new('1.0', 'UTF-8');
my $write = $schema->compile(WRITER => '{myns}mytype');
my $xml = $write->($doc, $hash);
print $xml->toString;
alternative
my $write = $schema->compile(WRITER => 'myns#myid');
"$schema->template('XML', ...)" creates an XML example
Based on the schema, this produces an XML message as example. Schemas are usually so
complex that people loose overview. This example may put you back on track, and used
as starting point for many creating the XML version of the message.
"$schema->template('PERL', ...)" creates an Perl example
Based on the schema, this produces an Perl HASH structure (a bit like the output by
Data::Dumper), which can be used as template for creating messages. The output
contains documentation, and is usually much clearer than the schema itself.
"$schema->template('TREE', ...)" creates a parse tree
To be able to produce Perl-text and XML examples, the templater generates an abstract
tree from the schema. That tree is returned here. Be warned that the structure is
not fixed over releases: add regression tests for this to your project.
Be warned that the schema is not validated; you can develop schemas which do work well
with this module, but are not valid according to W3C. In many cases, however, the
translater will refuse to accept mistakes: mainly because it cannot produce valid code.
See documentation in the base class.
METHODS
See documentation in the base class.
Constructors
See documentation in the base class.
XML::Compile::Schema->new([XMLDATA], OPTIONS)
Details about many name-spaces can be organized with only a single schema object
(actually, the data is administered in an internal XML::Compile::Schema::NameSpaces
object)
The initial information is extracted from the XMLDATA source. The XMLDATA can be
anything what is acceptable by importDefinitions(), which is everything accepted by
dataToXML() or an ARRAY of those things. You may also add any OPTION accepted by
addSchemas() to guide the understanding of the schema. When no XMLDATA is provided,
you can add it later with importDefinitions()
You can specify the hooks before you define the schemas the hooks work on: all schema
information and all hooks are only used when the readers and writers get compiled.
-Option --Defined in --Default
block_namespace []
hook undef
hooks []
ignore_unused_tags <false>
key_rewrite []
parser_options XML::Compile <many>
schema_dirs XML::Compile undef
typemap {}
block_namespace => NAMESPACE|TYPE|HASH|CODE|ARRAY
See blockNamespace()
hook => ARRAY-WITH-HOOKDATA | HOOK
See addHook(). Adds one HOOK (HASH).
hooks => ARRAY-OF-HOOK
See addHooks().
ignore_unused_tags => BOOLEAN|REGEXP
(WRITER) Usually, a "mistake" warning is produced when a user provides a data
structure which contains more data than is needed for the XML message which is
created; this will show structural problems. However, in some cases, you may want
to play tricks with the data-structure and therefore disable this precausion.
With a REGEXP, you can have more control. Only keys which do match the expression
will be ignored silently. Other keys (usually typos and other mistakes) will get
reported. See "Typemaps"
key_rewrite => HASH|CODE|ARRAY-of-HASH-and-CODE
Translate XML element local-names into different Perl keys. See "Key rewrite".
parser_options => HASH|ARRAY
schema_dirs => DIRECTORY|ARRAY-OF-DIRECTORIES
typemap => HASH
HASH of Schema type to Perl object or Perl class. See "Typemaps", the serialization
of objects.
Accessors
See documentation in the base class.
$obj->addHook(HOOKDATA|HOOK|undef)
HOOKDATA is a LIST of options as key-value pairs, HOOK is a HASH with the same data.
"undef" is ignored. See addHooks() and "Schema hooks" below.
$obj->addHooks(HOOK, [HOOK, ...])
Add multiple hooks at once. These must all be HASHes. See "Schema hooks" and
addHook(). "undef" values are ignored.
$obj->addKeyRewrite(PREDEF|CODE|HASH, ...)
Add new rewrite rules to the existing list (initially provided with new(key_rewrite)).
The whole list of rewrite rules is returned.
"PREFIXED" rules will be applied first. Special care is taken that the prefix will
not be called twice. The last added set of rewrite rules will be applied first. See
"Key rewrite".
$obj->addSchemaDirs(DIRECTORIES|FILENAME)
XML::Compile::Schema->addSchemaDirs(DIRECTORIES|FILENAME)
See "Accessors" in XML::Compile
$obj->addSchemas(XML, OPTIONS)
Collect all the schemas defined in the XML data. The XML parameter must be a
XML::LibXML node, therefore it is advised to use importDefinitions(), which has a much
more flexible way to specify the data.
When the object extends XML::Compile::Cache, the prefixes declared on the schema
element will be taken as default prefixes.
-Option --Default
attribute_form_default <undef>
element_form_default <undef>
filename undef
source undef
target_namespace <undef>
attribute_form_default => 'qualified'|'unqualified'
element_form_default => 'qualified'|'unqualified'
Overrule the default as found in the schema. Many old schemas (like WSDL11 and
SOAP11) do not specify the correct default element form in the schema but only in
the text.
filename => FILENAME
Explicitly state from which file the data is coming.
source => STRING
An indication where this schema data was found. If you use dataToXML() in LIST
context, you get such an indication.
target_namespace => NAMESPACE
Overrule (or set) the target namespace in the schema.
$obj->addTypemap(PAIR)
Synonym for addTypemap().
$obj->addTypemaps(PAIRS)
Add new XML-Perl type relations. See "Typemaps".
$obj->blockNamespace(NAMESPACE|TYPE|HASH|CODE|ARRAY)
Block all references to a NAMESPACE or full TYPE, as if they do not appear in the
schema. Specially useful if the schema includes references to old (deprecated)
versions of itself which are not being used. It can also be used to block inclusion
of huge structures which are not used, for increased compile performance, or to avoid
buggy constructs.
These values can also be passed with new(block_namespace) and
compile(block_namespace).
$obj->hooks([READER|WRITER])
Returns the LIST of defined hooks (as HASHes). [1.36] When an action parameter is
provided, it will only return a list with hooks added with that action value or no
action at all.
$obj->useSchema(SCHEMA, [SCHEMA])
Pass a XML::Compile::Schema object, or extensions like XML::Compile::Cache, to be used
as definitions as well. First, elements are looked-up in the current schema
definition object. If not found the other provided SCHEMA objects are checked in the
order as they were added.
Searches for definitions do not recurse into schemas which are used by the used
schema.
example: use other Schema
my $wsdl = XML::Compile::WSDL->new($wsdl);
my $geo = Geo::GML->new(version => '3.2.1');
# both $wsdl and $geo extend XML::Compile::Schema
$wsdl->useSchema($geo);
Compilers
See documentation in the base class.
$obj->compile(('READER'|'WRITER'), TYPE, OPTIONS)
Translate the specified ELEMENT (found in one of the read schemas) into a CODE
reference which is able to translate between XML-text and a HASH. When the TYPE is
"undef", an empty LIST is returned.
The indicated TYPE is the starting-point for processing in the data-structure, a
toplevel element or attribute name. The name must be specified in "{url}name" format,
there the url is the name-space. An alternative is the "url#id" which refers to an
element or type with the specific "id" attribute value.
When a READER is created, a CODE reference is returned which needs to be called with
XML, as accepted by XML::Compile::dataToXML(). Returned is a nested HASH structure
which contains the data from contained in the XML. The transformation rules are
explained below.
When a WRITER is created, a CODE reference is returned which needs to be called with
an XML::LibXML::Document object and a HASH, and returns a XML::LibXML::Node.
Many OPTIONS below are explained in more detailed in the manual-page
XML::Compile::Translate, which implements the compilation.
-Option --Default
abstract_types 'ERROR'
any_attribute undef
any_element undef
any_type <returns string or node>
attributes_qualified <undef>
block_namespace []
check_occurs <true>
check_values <true>
default_values <depends on backend>
elements_qualified <undef>
hook undef
hooks undef
ignore_facets <false>
ignore_unused_tags <false>
include_namespaces <true>
interpret_nillable_as_optional <false>
key_rewrite []
mixed_elements 'ATTRIBUTES'
namespace_reset <false>
output_namespaces undef
path <expanded name of type>
permit_href <false>
prefixes {}
sloppy_floats <false>
sloppy_integers <false>
typemap {}
use_default_namespace <false>
validation <true>
xsi_type {}
abstract_types => 'ERROR'|'ACCEPT'
How to handle the use abstract types. Of course, they should not be used, but
sometime they accidentally are. When set to "ERROR", an error will be produced
whenever an abstract type is encountered. "ACCEPT" will ignore the fact that the
types are abstract, and treat them as non-abstract types.
any_attribute => CODE|'TAKE_ALL'|'SKIP_ALL'
[0.89] In general, "anyAttribute" schema components cannot be handled automatically.
If you need to create or process anyAttribute information, then read about
wildcards in the DETAILS chapter of the manual-page for the specific back-end.
[pre-0.89] this option was named "anyElement", which will still work.
any_element => CODE|'TAKE_ALL'|'SKIP_ALL'
[0.89] In general, "any" schema components cannot be handled automatically. If you
need to create or process any information, then read about wildcards in the DETAILS
chapter of the manual-page for the specific back-end. [pre-0.89] this option was
named "anyElement", which will still work.
any_type => CODE
[1.07] how to handle "anyType" type elements. Depends on the backend.
attributes_qualified => BOOLEAN
When defined, this will overrule the "attributeFormDefault" flags in all schemas.
When not qualified, the xml will not produce nor process prefixes on attributes.
block_namespace => NAMESPACE|TYPE|HASH|CODE|ARRAY
See blockNamespace().
check_occurs => BOOLEAN
Whether code will be produced to do bounds checking on elements and blocks which may
appear more than once. When the schema says that maxOccurs is 1, then that element
becomes optional. When the schema says that maxOccurs is larger than 1, then the
output is still always an ARRAY, but now of unrestricted length.
check_values => BOOLEAN
Whether code will be produce to check that the XML fields contain the expected data
format.
Turning this off will improve the processing speed significantly, but is (of course)
much less safe. Do not set it off when you expect data from external sources:
validation is a crucial requirement for XML.
default_values => 'MINIMAL'|'IGNORE'|'EXTEND'
How to treat default values as provided by the schema. With "IGNORE" (the writer
default), you will see exactly what is specified in the XML or HASH. With "EXTEND"
(the reader default) will show the default and fixed values in the result.
"MINIMAL" does remove all fields which are the same as the default setting:
simplifies. See "Default Values".
elements_qualified => "TOP"|"ALL"|"NONE"|BOOLEAN
When defined, this will overrule the namespace use on elements in all schemas. When
"TOP" is specified, at least the top-element will be name-space qualified. When
"ALL" or a true value is given, then all elements will be used qualified. When
"NONE" or a false value is given, the XML will not produce or process prefixes on
the elements.
The "form" attributes will be respected, except on the top element when "TOP" is
specified. Use hooks when you need to fix name-space use in more subtile ways.
With "element_form_default", you can correct whole schema's about their name-space
behavior.
hook => HOOK|ARRAY-OF-HOOKS
Define one or more processing hooks. See "Schema hooks" below. These hooks are
only active for this compiled entity, where addHook() and addHooks() can be used to
define hooks which are used for all results of compile(). The hooks specified with
the "hook" or "hooks" option are run before the global definitions.
hooks => HOOK|ARRAY-OF-HOOKS
Alternative for option "hook".
ignore_facets => BOOLEAN
Facets influence the formatting and range of values. This does not come cheap, so
can be turned off. It affects the restrictions set for a simpleType. The
processing speed will improve, but validation is a crucial requirement for XML:
please do not turn this off when the data comes from external sources.
ignore_unused_tags => BOOLEAN|REGEXP
Overrules what is set with new(ignore_unused_tags).
include_namespaces => BOOLEAN|CODE
Indicates whether the WRITER should include the prefix to namespace translation on
the top-level element of the returned tree. If not, you may continue with the same
name-space table to combine various XML components into one, and add the namespaces
later. No namespace definition can be added the production rule produces an
attribute.
When a CODE reference is passed, it will be called for each namespace to decide
whether it should be included or not. When true, it will we added. The CODE is
called with a namespace, its prefix, and the number of times it was used for that
schema element translator.
interpret_nillable_as_optional => BOOLEAN
Found in the schema wild-life: people who think that nillable means optional. Not
too hard to fix. For the WRITER, you still have to state NIL explicitly, but the
elements are not constructed. The READER will output NIL when the nillable elements
are missing.
key_rewrite => HASH|CODE|ARRAY-of-HASH-and-CODE
Add key rewrite rules to the front of the list of rules, as set by new(key_rewrite)
and addKeyRewrite(). See "Key rewrite"
mixed_elements => CODE|PREDEFINED
What to do when mixed schema elements are to be processed. Read more in the
"DETAILS" section below.
namespace_reset => BOOLEAN
Use the same prefixes in "prefixes" as with some other compiled piece, but reset the
counts to zero first.
output_namespaces => HASH|ARRAY-of-PAIRS
[Pre-0.87] name for the "prefixes" option. Deprecated.
path => STRING
Prepended to each error report, to indicate the location of the error in the XML-
Scheme tree.
permit_href => BOOLEAN
When parsing SOAP-RPC encoded messages, the elements may have a "href" attribute
pointing to an object with "id". The READER will return the unparsed, unresolved
node when the attribute is detected, and the SOAP-RPC decoder will have to discover
and resolve it.
prefixes => HASH|ARRAY-of-PAIRS
Can be used to pre-define prefixes for namespaces (for 'WRITER' or key rewrite) for
instance to reserve common abbreviations like "soap" for external use. Each entry
in the hash has as key the namespace uri. The value is a hash which contains "uri",
"prefix", and "used" fields. Pass a reference to a private hash to catch this
index. An ARRAY with prefix, uri PAIRS is simpler.
prefixes => [ mine => $myns, two => $twons ]
prefixes => { $myns => 'mine', $twons => 'two' }
# the previous is short for:
prefixes => { $myns => [ uri => $myns, prefix => 'mine', used => 0 ]
, $twons => [ uri => $twons, prefix => 'two', ...] };
sloppy_floats => BOOLEAN
The float types of XML are all quite big, and support NaN, INF, and -INF. Perl's
normal floats do not, and therefore Math::BigFloat is used. This, however, is slow.
When true, you will crash on any value which is not understood by Perl's default
float... but run much faster. See also "sloppy_integers".
sloppy_integers => BOOLEAN
The XML "integer" data-types must support at least 18 digits, which is larger than
Perl's 32 bit internal integers. Therefore, the implementation will use
Math::BigInt objects to handle them. However, often an simple "int" type whould
have sufficed, but the XML designer was lazy. A long is much faster to handle. Set
this flag to use "int" as fast (but inprecise) replacements.
Be aware that "Math::BigInt" and "Math::BigFloat" objects are nearly but not fully
transparently mimicing the behavior of Perl's ints and floats. See their respective
manual-pages. Especially when you wish for some performance, you should optimize
access to these objects to avoid expensive copying which is exactly the spot where
the differences are.
You can also improve the speed of Math::BigInt by installing Math::BigInt::GMP. Add
"use Math::BigInt try => 'GMP';" to the top of your main script to get more
performance.
typemap => HASH
Add this typemap to the relations defined by new(typemap) or addTypemaps()
use_default_namespace => BOOLEAN
[0.91] When mixing qualified and unqualified namespaces, then the use of a default
namespace can be quite confusing: a name-space without prefix. Therefore, by
default, all qualified elements will have an explicit prefix.
validation => BOOLEAN
XML message must be validated, to lower the chance on abuse. However, of course, it
costs performance which is only partially compensated by fewer checks in your code.
This flag overrules the "check_values", "check_occurs", and "ignore_facets".
xsi_type => HASH
See "Handling xsi:type". The HASH maps types as mentioned in the schema, to
extensions of those types which are addressed via the horrible "xsi:type" construct.
When you specify "AUTO" as value, the translator tries to auto-detect. This may be
slow and may produce incomplete results.
$obj->dataToXML( NODE|REF-XML-STRING|XML-STRING|FILENAME|FILEHANDLE|KNOWN )
XML::Compile::Schema->dataToXML( NODE|REF-XML-STRING|XML-STRING|FILENAME|FILEHANDLE|KNOWN
)
See "Compilers" in XML::Compile
$obj->initParser(OPTIONS)
XML::Compile::Schema->initParser(OPTIONS)
See "Compilers" in XML::Compile
$obj->template('XML'|'PERL'|'TREE', ELEMENT, OPTIONS)
Schema's can be horribly complex and unreadible. Therefore, this template method can
be called to create an example which demonstrates how data of the specified ELEMENT
shown as XML or Perl is organized in practice.
The 'TREE' template returns the intermediate parse tree, which gets formatted into the
XML or Perl example. This is not a very stable interface: it may change without much
notice.
Some OPTIONS are explained in XML::Compile::Translate. There are some extra OPTIONS
defined for the final output process.
The templates produced are not always correct. Please contribute improvements: read
and understand the comments in the text.
-Option --Default
abstract_types 'ERROR'
attributes_qualified <undef>
elements_qualified 'TOP'
include_namespaces <true>
indent " "
key_rewrite []
show_comments ALL
skip_header <false>
abstract_types => 'ERROR'|'ACCEPT'
By default, do not show abstract types in the output.
attributes_qualified => BOOLEAN
elements_qualified => 'ALL'|'TOP'|'NONE'|BOOLEAN
include_namespaces => BOOLEAN|CODE
indent => STRING
The leading indentation string per nesting. Must start with at least one blank.
key_rewrite => HASH|CODE|ARRAY-of-HASH-and-CODE
show_comments => STRING|'ALL'|'NONE'
A comma separated list of tokens, which explain what kind of comments need to be
included in the output. The available tokens are: "struct", "type", "occur",
"facets". A value of "ALL" will select all available comments. The "NONE" or empty
string will exclude all comments.
skip_header => BOOLEAN
Skip the comment header from the output.
Administration
See documentation in the base class.
$obj->doesExtend(EXTTYPE, BASETYPE)
Returns true when the EXTTYPE extends the BASETYPE. See
XML::Compile::Schema::NameSpaces::doesExtend()
$obj->elements()
List all elements, defined by all schemas sorted alphabetically.
$obj->findSchemaFile(FILENAME)
XML::Compile::Schema->findSchemaFile(FILENAME)
See "Administration" in XML::Compile
$obj->importDefinitions(XMLDATA, OPTIONS)
Import (include) the schema information included in the XMLDATA. The XMLDATA must be
acceptable for dataToXML(). The resulting node and all the OPTIONS are passed to
addSchemas(). The schema node does not need to be the top element: any schema node
found in the data will be decoded.
Returned is a list of XML::Compile::Schema::Instance objects, for each processed
schema component.
If your program imports the same string or file definitions multiple times, it will
re-use the schema information from the first import. This removal of dupplications
will not work for open files or pre-parsed XML structures.
As an extension to the handling dataToXML() provides, you can specify an ARRAY of
things which are acceptable to "dataToXML". This way, you can specify multiple
resources at once, each of which will be processed with the same OPTIONS.
-Option --Default
details <from XMLDATA>
details => HASH
Overrule the details information about the source of the data.
example: of use of importDefinitions
my $schema = XML::Compile::Schema->new;
$schema->importDefinitions('my-spec.xsd');
my $other = "<schema>...</schema>"; # use 'HERE' documents!
my @specs = ('my-spec.xsd', 'types.xsd', $other);
$schema->importDefinitions(\@specs, @options);
$obj->knownNamespace(NAMESPACE|PAIRS)
XML::Compile::Schema->knownNamespace(NAMESPACE|PAIRS)
See "Administration" in XML::Compile
$obj->namespaces()
Returns the XML::Compile::Schema::NameSpaces object which is used to collect schemas.
$obj->printIndex([FILEHANDLE], OPTIONS)
Print all the elements which are defined in the schemas to the FILEHANDLE (by default
the selected handle). OPTIONS are passed to
XML::Compile::Schema::NameSpaces::printIndex() and
XML::Compile::Schema::Instance::printIndex().
$obj->types()
List all types, defined by all schemas sorted alphabetically.
$obj->walkTree(NODE, CODE)
See "Administration" in XML::Compile
DETAILS
See documentation in the base class.
Distribution collection overview
See documentation in the base class.
Comparison
See documentation in the base class.
Collecting definitions
When starting an application, you will need to read the schema definitions. This is done
by instantiating an object via XML::Compile::Schema::new() or XML::Compile::WSDL11::new().
The WSDL11 object has a schema object internally.
Schemas may contains "import" and "include" statements, which specify other resources for
definitions. In the idea of the XML design team, those files should be retrieved
automatically via an internet connection from the "schemaLocation". However, this is a
bad concept; in XML::Compile modules you will have to explicitly provide filenames on
local disk using importDefinitions() or XML::Compile::WSDL11::addWSDL().
There are various reasons why I, the author of this module, think the dynamic automatic
internet imports are a bad idea. First: you do not always have a working internet
connection (travelling with a laptop in a train). Your implementation should work the
same way under all environmental circumstances! Besides, I do not trust remote files on
my system, without inspecting them. Most important: I want to run my regression tests
before using a new version of the definitions, so I do not want to have a remote server
change the agreements without my knowledge.
So: before you start, you will need to scan (recursively) the initial schema or wsdl file
for "import" and "include" statements, and collect all these files from their
"schemaLocation" into files on local disk. In your program, call importDefinitions() on
all of them -in any order- before you call compile().
Organizing your definitions
One nice feature to help you organize (especially useful when you package your code in a
distribution), is to add these lines to the beginning of your code:
package My::Package;
XML::Compile->addSchemaDirs(__FILE__);
XML::Compile->knownNamespace('http://myns' => 'myns.xsd', ...);
Now, if the package file is located at "SomeThing/My/Package.pm", the definion of the
namespace should be kept in "SomeThing/My/Package/xsd/myns.xsd".
Somewhere in your program, you have to load these definitions:
# absolute or relative path is always possible
$schema->importDefinitions('SomeThing/My/Package/xsd/myns.xsd');
# relative search path extended by addSchemaDirs
$schema->importDefinitions('myns.xsd');
# knownNamespace improves abstraction
$schema->importDefinitions('http://myns');
Very probably, the namespace is already in some variable:
use XML::Compile::Schema;
use XML::Compile::Util 'pack_type';
my $myns = 'http://some-very-long-uri';
my $schema = XML::Compile::Schema->new($myns);
my $mytype = pack_type $myns, $myelement;
my $reader = $schema->compileClient(READER => $mytype);
Addressing components
Normally, external users can only address elements within a schema, and types are hidden
to be used by other schemas only. For this reason, it is permitted to create an element
and a type with the same name.
The compiler requires a starting-point. This can either be an element name or an
element's id. The format of the element name is "{namespace-uri}localname", for instance
{http://library}book
You may also start with
http://www.w3.org/2001/XMLSchema#float
as long as this ID refers to a top-level element, not a type.
When you use a schema without "targetNamespace" (which is bad practice, but sometimes
people really do not understand the beneficial aspects of the use of namespaces) then the
elements can be addressed as "{}name" or simple "name".
Representing data-structures
The code will do its best to produce a correct translation. For instance, an accidental
1.9999 will be converted into 2 when the schema says that the field is an "int". It will
also strip superfluous blanks when the data-type permits. Especially watch-out for the
"Integer" types, which produce Math::BigInt objects unless compile(sloppy_integers) is
used.
Elements can be complex, and themselve contain elements which are complex. In the Perl
representation of the data, this will be shown as nested hashes with the same structure as
the XML.
You should not take tare of character encodings, whereas XML::LibXML is doing that for us:
you shall not escape characters like "<" yourself.
The schemas define kinds of data types. There are various ways to define them (with
restrictions and extensions), but for the resulting data structure is that knowledge not
important.
simpleType
A single value. A lot of single value data-types are built-in (see
XML::Compile::Schema::BuiltInTypes).
Simple types may have range limiting restrictions (facets), which will be checked by
default. Types may also have some white-space behavior, for instance blanks are stripped
from integers: before, after, but also inside the number representing string.
Note that some of the reader hooks will alter the single value of these elements into a
HASH like used for the complexType/simpleContent (next paragraph), to be able to return
some extra collected information.
complexType/simpleContent
In this case, the single value container may have attributes. The number of attributes
can be endless, and the value is only one. This value has no name, and therefore gets a
predefined name "_".
When passed to the writer, you may specify a single value (not the whole HASH) when no
attributes are used.
complexType and complexType/complexContent
These containers not only have attributes, but also multiple values as content. The
"complexContent" is used to create inheritance structures in the data-type definition.
This does not affect the XML data package itself.
Manually produced XML NODE
For a WRITER, you may also specify a XML::LibXML::Node anywhere.
test1 => $doc->createTextNode('42');
test3 => $doc->createElement('ariba');
This data-structure is used without validation, so you are fully on your own with this
one. Typically, nodes are produced by hooks to implement work-arounds.
Occurence
A second factor which determines the data-structure is the element occurrence. Usually,
elements have to appear once and exactly once on a certain location in the XML data
structure. This order is automatically produced by this module. But elements may appear
multiple times.
usual case
The default behavior for an element (in a sequence container) is to appear exactly
once. When missing, this is an error.
maxOccurs larger than 1
In this case, the element or particle block can appear multiple times. Multiple
values are kept in an ARRAY within the HASH. Non-schema based XML modules do not
return a single value as an ARRAY, which makes that code more complicated. But in our
case, we know the expected amount beforehand.
When the maxOccurs larger than 1 is specified for an element, an ARRAY of those
elements is produced. When it is specified for a block (sequence, choice, all,
group), then an ARRAY of HASHes is returned. See the special section about this
subject.
An error is produced when the number of elements found is less than "minOccurs"
(defaults to 1) or more than "maxOccurs" (defaults to 1), unless compile(check_occurs)
is "false".
Example elements with maxOccurs larger than 1. In the schema:
<element name="a" type="int" maxOccurs="unbounded" />
<element name="b" type="int" />
In the XML message:
<a>12</a><a>13</a><b>14</b>
In the Perl representation:
a => [12, 13], b => 14
value is "NIL"
When an element is nillable, that is explicitly represented as a "NIL" constant
string.
use="optional" or minOccurs="0"
The element may be skipped. When found it is a single value.
use="forbidden"
When the element is found, an error is produced.
default="value"
When the XML does not contain the element, the default value is used... but only if
this element's container exists. This has no effect on the writer.
fixed="value"
Produce an error when the value is not present or different (after the white-space
rules where applied).
Default Values
[added in v0.91] With compile(default_values) you can control how much information about
default values defined by the schema will be passed into your program.
The choices, available for both READER and WRITER, are:
"IGNORE" (the WRITER's standard behavior)
Only include element and attribute values in the result if they are in the XML
message. Behaviorally, this treats elements with default values as if they are just
optional. The WRITER does not try to be smarter than you.
"EXTEND" (the READER's standard behavior)
If some element or attribute is not in the source but has a default in the schema,
that value will be produced. This is very convenient for the READER, because your
application does not have to hard-code the same constant values as defaults as well.
"MINIMAL"
Only produce the values which differ from the defaults. This choice is useful when
producing XML, to reduce the size of the output.
Repetative blocks
Particle blocks come in four shapes: "sequence", "choice", "all", and "group" (an indirect
block). This also affects "substitutionGroups".
repetative sequence, choice, all
In situations like this:
<element name="example">
<complexType>
<sequence>
<element name="a" type="int" />
<sequence>
<element name="b" type="int" />
</sequence>
<element name="c" type="int" />
</sequence>
</complexType>
</element>
(yes, schemas are verbose) the data structure is
<example> <a>1</a> <b>2</b> <c>3</c> </example>
the Perl representation is flattened, into
example => { a => 1, b => 2, c => 3 }
Ok, this is very simple. However, schemas can use repetition:
<element name="example">
<complexType>
<sequence>
<element name="a" type="int" />
<sequence minOccurs="0" maxOccurs="unbounded">
<element name="b" type="int" />
</sequence>
<element name="c" type="int" />
</sequence>
</complexType>
</element>
The XML message may be:
<example> <a>1</a> <b>2</b> <b>3</b> <b>4</b> <c>5</c> </example>
Now, the perl representation needs to produce an array of the data in the repeated block.
This array needs to have a name, because more of these blocks may appear together in a
construct. The name of the block is derived from the type of block and the name of the
first element in the block, regardless whether that element is present in the data or not.
So, our example data is translated into (and vice versa)
example =>
{ a => 1
, seq_b => [ {b => 2}, {b => 3}, {b => 4} ]
, c => 5
}
The following label is used, based on the name of the first element (say "xyz") as defined
in the schema (not in the actual message):
seq_xyz sequence with maxOccurs > 1
cho_xyz choice with maxOccurs > 1
all_xyz all with maxOccurs > 1
When you have compile(key_rewrite) option PREFIXED, and you have explicitly assigned the
prefix "xs" to the schema namespace (See compile(prefixes)), then those names will
respectively be "seq_xs_xyz", "cho_xs_xyz", "all_xs_xyz".
repetative groups
[behavioral change in 0.93] In contrast to the normal partical blocks, as described above,
do the groups have names. In this case, we do not need to take the name of the first
element, but can use the group name. It will still have "gr_" appended, because groups
can have the same name as an element or a type(!)
Blocks within the group definition cannot be repeated.
repetative substitutionGroups
For substitutionGroups which are repeating, the name of the base element is used (the
element which has attribute "<abstract="true"">. We do need this array, because the order
of the elements within the group may be important; we cannot group the elements based to
the extended element's name.
In an example substitutionGroup, the Perl representation will be something like this:
base-element-name =>
[ { extension-name => $data1 }
, { other-extension => $data2 }
]
Each HASH has only one key.
List type
List simpleType objects are also represented as ARRAY, like elements with a minOccurs or
maxOccurs unequal 1.
Using substitutionGroup constructs
A substitution group is kind-of choice between alternative (complex) types. However, in
this case roles have reversed: instead a "choice" which lists the alternatives, here the
alternative elements register themselves as valid for an abstract (head) element. All
alternatives should be extensions of the head element's type, but there is no way to check
that.
Wildcards any and anyAttribute
The "any" and "anyAttribute" elements are referred to as "wildcards": they specify groups
of elements and attributes which can be used, in stead of being explicit.
The author of this module advices against the use of wildcards in schemas, because the
purpose of schemas is to be explicit about the structure of the message, and that basic
idea is simply thrown away by these wildcards. Let people cleanly extend the schema with
inheritance! If you use a standard schema which facilitates these wildcards, then please
do not use them!
Because wildcards are not explicit about the types to expect, the "XML::Compile" module
can not prepare for them automatically. However, as user of the schema you probably know
better about the possible contents of these fields. Therefore, you can translate that
knowledge into code explicitly. Read about the processing of wildcards in the manual page
for each of the back-ends, because it is different in each case.
ComplexType with "mixed" attribute
[largely improved in 0.86, reader only] ComplexType and ComplexContent components can be
declared with the "<mixed="true""> attribute. This implies that text is not limited to
the content of containers, but may also be used inbetween elements. Usually, you will
only find ignorable white-space between elements.
In this example, the "a" container is marked to be mixed:
<a> before <b>2</b> after </a>
Each back-end has its own way of handling mixed elements. The compile(mixed_elements)
currently only modifies the reader's behavior; the writer's capabilities are limited. See
XML::Compile::Translate::Reader.
hexBinary and base64Binary
These are used to include images and such in an XML message. Usually, they are quite large
with respect to the other elements. When you use SOAP, you may wish to use
XML::Compile::XOP instead.
The element values which you need to pass for fields of these types is a binary BLOB,
something Perl does not have. So, it is a string containing binary data but not specially
marked that way.
If you need to store an integer in such a binary field, you first have to promote it into
a BLOB (string) like this
{ color => pack('N', $i) } # writer
my $i = unpack('N', $d->{color}); # reader
Module Geo::KML implements a nice hook to avoid the explicit need for this "pack" and
"unpack". The KML schema designers liked colors to be written as "ffc0c0c0" and abused
"hexBinary" for that purpose. The "colorType" fields in KML are treated as binary, but
just represent an int. Have a look in that Geo::KML code if your schema has some of those
tricks.
Schema hooks
You can use hooks, for instance, to block processing parts of the message, to create work-
arounds for schema bugs, or to extract more information during the process than done by
default.
Defining hooks
Multiple hooks can active during the compilation process of a type, when "compile()" is
called. During Schema translation, each of the hooks is checked for all types which are
processed. When multiple hooks select the object to get a modified behavior, then all are
evaluated in order of definition.
Defining a global hook (where HOOKDATA is the LIST of PAIRS with hook parameters, and HOOK
a HASH with such HOOKDATA):
my $schema = XML::Compile::Schema->new
( ...
, hook => HOOK
, hooks => [ HOOK, HOOK ]
);
$schema->addHook(HOOKDATA | HOOK);
$schema->addHooks(HOOK, HOOK, ...);
my $wsdl = XML::Compile::WSDL->new(...);
$wsdl->addHook(HOOKDATA | HOOK);
local hooks are only used for one reader or writer. They are evaluated before the global
hooks.
my $reader = $schema->compile(READER => $type
, hook => HOOK, hooks => [ HOOK, HOOK, ...]);
General syntax
Each hook has three kinds of parameters:
. selectors
. processors
. action ('READER' or 'WRITER', defaults to both)
Selectors define the schema component of which the processing is modified. When one of
the selectors matches, the processing information for the hook is used. When no selector
is specified, then the hook will be used on all elements.
Available selectors (see below for details on each of them):
. type
. id
. path
As argument, you can specify one element as STRING, a regular expression to select
multiple elements, or an ARRAY of STRINGs and REGEXes.
Next to where the hook is placed, we need to known what to do in the case: the hook
contains processing information. When more than one hook matches, then all of these
processors are called in order of hook definition. However, first the compile hooks are
taken, and then the global hooks.
How the processing works exactly depends on the compiler back-end. There are major
differences. Each of those manual-pages lists the specifics. The label tells us when the
processing is initiated. Available labels are "before", "replace", and "after".
Hooks on matching types
The "type" selector specifies a complexType of simpleType by name. Best is to base the
selection on the full name, like "{ns}type", which will avoid all kinds of name-space
conflicts in the future. However, you may also specify only the "type" (in any name-
space). Any REGEX will be matched to the full type name. Be careful with the pattern
archors.
If you use XML::Compile::Cache [release 0.90], then you can use "prefix:type" as type
specification as well. You have to explicitly define prefix to namespace beforehand.
Hooks on matching ids
Matching based on IDs can reach more schema elements: some types are anonymous but still
have an ID. Best is to base selection on the full ID name, like "ns#id", to avoid all
kinds of name-space conflicts in the future.
Hooks on matching paths
When you see error messages, you always see some representation of the path where the
problem was discovered. You can use this path as selector, when you know what it is... BE
WARNED, that the current structure of the path is not really consequent hence will be
improved in one of the future releases, breaking backwards compatibility.
Typemaps
Often, XML will be used in object oriented programs, where the facts which are transported
in the XML message are attributes of Perl objects. Of course, you can always collect the
data from each of the Objects into the required (huge) HASH manually, before triggering
the reader or writer. As alternative, you can connect types in the XML schema with Perl
objects and classes, which results in cleaner code.
You can also specify typemaps with new(typemap), addTypemaps(), and compile(typemap). Each
type will only refer to the last map for that type. When an "undef" is given for a type,
then the older definition will be cancelled. Examples of the three ways to specify
typemaps:
my %map = ($x1 => $p1, $x2 => $p2);
my $schema = XML::Compile::Schema->new(...., typemap => \%map);
$schema->addTypemaps($x3 => $p3, $x4 => $p4, $x1 => undef);
my $call = $schema->compile(READER => $type, typemap => \%map);
The latter only has effect for the type being compiled. The definitions are cumulative.
In the second example, the $x1 gets disabled.
Objects can come in two shapes: either they do support the connection with XML::Compile
(implementing two methods with predefined names), or they don't, in which case you will
need to write a little wrapper.
use XML::Compile::Util qw/pack_type/;
my $t1 = pack_type $myns, $mylocal;
$schema->typemap($t1 => 'My::Perl::Class');
$schema->typemap($t1 => $some_object);
$schema->typemap($t1 => sub { ... });
The implementation of the READER and WRITER differs. In the READER case, the typemap is
implemented as an 'after' hook which calls a "fromXML" method. The WRITER is a 'before'
hook which calls a "toXML" method. See respectively the XML::Compile::Translate::Reader
and XML::Compile::Translate::Writer.
Private variables in objects
When you design a new object, it is possible to store the information exactly like the
corresponding XML type definition. The only thing the "fromXML" has to do, is bless the
data-structure into its class:
$schema->typemap($xmltype => 'My::Perl::Class');
package My::Perl::Class;
sub fromXML { bless $_[1], $_[0] } # for READER
sub toXML { $_[0] } # for WRITER
However... the object may also need so need some private variables. If you store them in
the same HASH for your object, you will get "unused tags" warnings from the writer. To
avoid that, choose one of the following alternatives:
# never complain about unused tags
::Schema->new(..., ignore_unused_tags => 1);
# only complain about unused tags not matching regexp
my $not_for_xml = qr/^[A-Z]/; # my XML only has lower-case
::Schema->new(..., ignore_unused_tags => $not_for_xml);
# only for one compiled WRITER (not used with READER)
::Schema->compile(..., ignore_unused_tags => 1);
::Schema->compile(..., ignore_unused_tags => $not_for_xml);
Typemap limitations
There are some things you need to know:
. Many schemas define very complex types. These may often not translate cleanly into
objects. You may need to create a typemap relation for some parent type. The CODE
reference may be very useful in this case.
. A same kind of problem appears when you have a list in your object, which often is not
named in the schema.
Handling xsi:type
[1.10] The "xsi:type" is an old-fashioned mechanism, and should be avoided! In this case,
the schema does tell you that a certain element has a certrain type, but at run-time(!)
that is changed. When an XML element has a "xsi:type" attribute, it tells you simply to
have an extension of the original type. This whole mechanism does bite the "compilation"
idea of XML::Compile... however with some help, it will work.
To make "xsi:type" work at run-time, you have to pass a table of which types you expect at
compile-time. Example:
my %xsi_type_table =
( $base_type1 => [ $ext1_of_type1, $ext2_of_type2 ]
, $base_type2 => [ $ext1_of_type2 ]
);
my $r = $schema->compile(READER => $type
, xsi_type => \%xsi_type_table
);
When your schema is an XML::Compile::Cache (version at least 0.93), your types look like
"prefix:local". With a plain XML::Compile::Schema, they will look like
"{namespace}local", typically produced with XML::Compile::Util::pack_type().
When used in a reader, the resulting data-set will contain a "XSI_TYPE" key inbetween the
facts which were taken from the element. The type is is long syntax "{$ns}$type". See
XML::Compile::Util::unpack_type()
With the writer, you have to provide such an "XSI_TYPE" value or the element's base type
will be used (and no "xsi:type" attribute created). This will probably cause warnings
about unused tags. The type can be provided in full (see XML::Compile::Util::pack_type())
or [1.31] prefixed.
[1.25] then the value is not an ARRAY, but only the keyword "AUTO", the parser will try to
auto-detect all types which are valid alternatives. This currently only works for non-
builtin types. The auto-detection might be slow and (because many schemas are broken) not
produce a complete list. When debugging is enabled ("use Log::Report mode => 3;") you
will see to which list this AUTO gets expanded.
xsi_type => { $base_type => 'AUTO' } # requires X::C v1.25
XML::Compile::Cache (since v1.01) makes using "xsi:type" easier. When you have a ::Cache
based object (for instance a XML::Compile::WSDL11) you can simply say
$wsdl->addXsiType( $base_type => 'AUTO' )
Now, you do not need to pass the xsi table to each compilation call.
Key rewrite
[improved with release 1.10] The standard practice is to use the localName of the XML
elements as key in the Perl HASH; the key rewrite mechanism is used to change that,
sometimes to separate elements which have the same localName within different name-spaces,
or when an element and an attribute share a name (key rewrite is applied to elements AND
attributes) in other cases just for fun or convenience.
Rewrite rules are interpreted at "compile-time", which means that they do not slow-down
the XML construction or deconstruction. The rules work the same for readers and writers,
because they are applied to name found in the schema.
Key rewrite rules can be set during schema object initiation with new(key_rewrite) and to
an existing schema object with addKeyRewrite(). These rules will be used in all calls to
compile().
Next, you can use compile(key_rewrite) to add rules which are only used for a single
compilation. These are applied before the global rules. All rules will always be
attempted, and the rulle will me applied to the result of the previous change.
The last defined rewrite rules will be applied first, with one major exception: the
"PREFIXED" rules will be executed before any other rule.
key_rewrite via table
When a HASH is provided as rule, then the XML element name is looked-up. If found, the
value is used as translated key.
First full name of the element is tried, and then the localName of the element. The full
name can be created with XML::Compile::Util::pack_type() or by hand:
use XML::Compile::Util qw/pack_type/;
my %table =
( pack_type($myns, 'el1') => 'nice_name1'
, "{$myns}el2" => 'alsoNice'
, el3 => 'in any namespace'
);
$schema->addKeyRewrite( \%table );
Rewrite via function
When a CODE reference is provided, it will get called for each key which is found in the
schema. Passed are the name-space of the element and its local-name. Returned is the
key, which may be the local-name or something else.
For instance, some people use capitals in element names and personally I do not like them:
sub dont_like_capitals($$)
{ my ($ns, $local) = @_;
lc $local;
}
$schema->addKeyRewrite( \&dont_like_capitals );
for short:
my $schema = XML::Compile::Schema->new( ...,
key_rewrite => sub { lc $_[1] } );
key_rewrite when localNames collide
Let's start with an appology: we cannot auto-detect when these rewrite rules are needed,
because the colliding keys are within the same HASH, but the processing is fragmented over
various (sequence) blocks: the parser does not have the overview on which keys of the HASH
are used for which elements.
The problem occurs when one complex type or substitutionGroup contains multiple elements
with the same localName, but from different name-spaces. In the perl representation of
the data, the name-spaces get ignored (to make the programmer's life simple) but that may
cause these nasty conflicts.
Rewrite for convenience
In XML, we often see names like "my-elem-name", which in Perl would be accessed as
$h->{'my-elem-name'}
In this case, you cannot leave-out the quotes in your perl code, which is quite
inconvenient, because only 'barewords' can be used as keys unquoted. When you use option
"key_rewrite" for compile() or new(), you could decide to map dashes onto underscores.
key_rewrite
=> sub { my ($ns, $local) = @_; $local =~ s/\-/_/g; $local }
key_rewrite => sub { $_[1] =~ s/\-/_/g; $_[1] }
then "my-elem-name" in XML will get mapped onto "my_elem_name" in Perl, both in the READER
as the WRITER. Be warned that the substitute command returns the success, not the
modified value!
Pre-defined key_rewrite rules
UNDERSCORES
Replace dashes (-) with underscores (_).
SIMPLIFIED
Rewrite rule with the constant name (STRING) "SIMPLIFIED" will replace all dashes with
underscores, translate capitals into lowercase, and remove all other characters which
are none-bareword (if possible, I am too lazy to check)
PREFIXED
This requires a table for prefix to name-space translations, via compile(prefixes),
which defines at least one non-empty (default) prefix. The keys which represent
elements in any name-space which has a prefix defined will have that prefix and an
underscore prepended.
Be warned that the name-spaces which you provide are used, not the once used in the
schema. Example:
my $r = $schema->compile
( READER => $type
, prefixes => [ mine => $myns ]
, key_rewrite => 'PREFIXED'
);
my $xml = $r->( <<__XML );
<data xmlns="$myns"><x>42</x></data>
__XML
print join ' => ', %$xml; # mine_x => 42
PREFIXED(...)
Like the previous, but now only use a selected sub-set of the available prefixes.
This is particular useful in writers, when explicit prefixes are also used to beautify
the output.
The prefixes are not checked against the prefix list, and may have surrounding blanks.
key_rewrite => 'PREFIXED(opt,sar)'
Above is equivalent to:
key_rewrite => [ 'PREFIXED(opt)', 'PREFIXED(sar)' ]
Special care is taken that the prefix will not be added twice. For instance, if the
same prefix appears twice, or a "PREFIXED" rule is provided as well, then still only
one prefix is added.
SEE ALSO
This module is part of XML-Compile distribution version 1.42, built on January 06, 2014.
Website: http://perl.overmeer.net/xml-compile/
Other distributions in this suite: XML::Compile, XML::Compile::SOAP, XML::Compile::WSDL11,
XML::Compile::SOAP12, XML::Compile::SOAP::Daemon, XML::Compile::SOAP::WSA,
XML::Compile::C14N, XML::Compile::WSS, XML::Compile::WSS::Signature, XML::Compile::Tester,
XML::Compile::Cache, XML::Compile::Dumper, XML::Compile::RPC, XML::Rewrite and
XML::LibXML::Simple.
Please post questions or ideas to the mailinglist at
http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/xml-compile . For live contact with
other developers, visit the "#xml-compile" channel on "irc.perl.org".
LICENSE
Copyrights 2006-2014 by [Mark Overmeer]. For other contributors see ChangeLog.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself. See http://www.perl.com/perl/misc/Artistic.html