Qore XML Module: Qore XML Module

Qore XML Module 1.1

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Qore XML Module

Contents of this documentation:

- Introduction
- Module Option Constants
- Automatic XML Serialization and Deserialization
- XML-RPC
- Function and Method Tags
- WSDL user module
- SoapClient user module
- SoapHandler user module
- XmlRpcHandler user module
- Release Notes

# Introduction

XML functionality in the Qore xml module is provided by the libxml2 library, which provides a powerful, stable, clean, and thread-safe basis for XML integration in Qore. XML provides a way to describe hierarchical data, and thanks to libxml2, the xml module allows for easy serialization and deserialization between XML strings and Qore data structures.

This module is released under a choice of two licenses:

- LGPL 2.1
- MIT (see COPYING.MIT in the source distribution for more information)

The module is tagged as such in the module's header (meaning it can be loaded unconditionally regardless of how the Qore library was initialized).

To use the module in a Qore script, use the `%requires` directive as follows:

%requires xml

Note
  XML functionality was included in the main Qore shared library until version 0.8.1, at which time the code was removed to make this module.

Also included with the binary xml module:

- WSDL user module
- SoapClient user module
- SoapHandler user module
- XmlRpcHandler user module

# Module Option Constants

The following constants give information about the availability of XML functionality (dependent on libxml2 features at compile time):

XML Option Constants

Name | Type | Description
HAVE_PARSEXMLWITHRELAXNG | `bool` | Indicates if parseXMLWithRelaxNG() and Qore::Xml::XmlReader::relaxNGValidate() are available
HAVE_PARSEXMLWITHSCHEMA | `bool` | Indicates if parseXMLWithSchema() and Qore::Xml::XmlReader::schemaValidate() are available

If either of the above constants are `False`, then calling any of the dependent functions or methods will result in a run-time exception.

# Automatic XML Serialization and Deserialization

This section describes automatic XML serialization and deserialization; for iterative or user-controlled XML parsing, see XML Classes.

XML serialization (conversion from Qore data structures to XML strings) in the xml module relies on the fact that Qore hashes retain insertion order, which means that conversion to and from Qore data structures and XML strings can be done without data loss and without reordering the XML elements. In general, XML serialization is relatively straighforward, but there are a few issues to be aware of, particularly regarding element attributes and lists. These issues are described in the following paragraphs.

First, a straightforward example:

$h = ("record": ("name": ("first": "Fred", "last": "Smith")));
printf("%s\n", makeFormattedXMLString($h));

This produces the following result

    <?xml version="1.0" encoding="UTF-8"?>
    <record>
      <name>
        <first>Fred</first>
        <last>Smith</last>
      </name>
    </record>

To set XML attributes, the Qore value must be a hash and the attributes are stored in another hash in the key `"^attributes^"`. That is; the value of the `"^attributes^"` key must be a hash, and each member of this hash will represent an attribute-value pair.

For example:

$h = ("record": ("^attributes^": ("type": "customer") ,
"name": ("first": "Fred", "last": "Smith")));
printf("%s\n", makeFormattedXMLString($h));

This produces the following results:

    <?xml version="1.0" encoding="UTF-8"?>
    <record type="customer">
      <name>
        <first>Fred</first>
        <last>Smith</last>
      </name>
    </record>

If instead we wanted to have text instead of child data under the "record" node, we must set the `"^value^"` key of the hash along with the `"^attributes^"` key as follows:

$h = ("record": ("^attributes^": ("type": "customer"),
"^value^": "NO-RECORD"));
printf("%s\n", makeFormattedXMLString($h));

Giving the following results:

    <?xml version="1.0" encoding="UTF-8"?>
    <record type="customer">NO-RECORD</record>

Arrays are serialized with repeating node names as follows:

$h = ("record": ("part": ("part-02-05", "part-99-23", "part-34-28")));
printf("%s\n", makeFormattedXMLString($h));

Producing the following results:

    <?xml version="1.0" encoding="UTF-8"?>
    <record type="customer">
      <part>part-02-05</part>
      <part>part-99-23</part>
      <part>part-34-28</part>
    </record>

It gets a little trickier when a key should repeated at the same level in an XML string, but other keys come between, for example, take the following XML string:

    <?xml version="1.0" encoding="UTF-8"?>
    <para>Keywords: <code>this</code>, <code>that</code>, and <code>the_other</code>.</para>

It's not possible to use a list, because text is required in between. As described earlier, the `"^value^"` hash key can be used to serialize text in an XML string. In this case, we need to have several text nodes and several code nodes in a mixed-up order to give us the XML string we want. Because qore hases have unique keys (we can't use the same key twice in the same hash), we resort to a key naming trick that allows us to virtually duplicate our key names and therefore arrive at the XML string we want. We do this by appending a `'^'` character to the end of the key name and then some unique text. When serializing hash keys, any text after (and including) the `'^'` character is ignored. For the special key name `"^value^"`, we do not need to duplicate the final `'^'` character. Instead we just add unique text to ensure that our hash can contain all the data we want and that it will be serialized in the right order to the XML string as follows:

$h = ("para": ("^value^": "Keywords: ",
"code" : "this",
"^value^1" : ", ",
"code^1" : "that",
"^value^2" : ", and ",
"code^2" : "the_other",
"^value^3" : "."));
printf("%s\n", makeFormattedXMLString($h));

By ignoring the text after the `'^'` character, the above code will serialize to the XML string we want. In general, by using this convention, we can properly serialize multiple out-of-order keys without losing data and still have unique names for our hash keys.

Note than when deserializing XML strings to Qore data structures, the above rules are applied in reverse. If any out-of-order duplicate keys are detected, Qore will automatically generate unique hash key names based on the above rules.

Also note that `CDATA` text will be generated if a hash key starts with `'^cdata'`; such text will not be processed for escape code substitution. When deserializing XML strings to qore data structures, CDATA text will be placed unmodified under such a hash key as well.

Functions For XML Serialization and Deserialization

Function Name | Description
makeFormattedXMLFragment() | Serializes a hash into an XML string with formatting without an XML header.
makeFormattedXMLString() | Serializes a hash into an XML string with formatting and an XML header.
makeXMLFragment() | Serializes a hash into an XML string without an XML header or formatting.
makeXMLString() | Serializes a hash into a complete XML string with an XML header and without formatting.
parseXMLAsData() | parses an XML string as data (duplicate, out-of-order XML elements are collapsed into lists) and returns a Qore hash structure.
parseXMLAsDataWithRelaxNG() | parses an XML string as data (duplicate, out-of-order XML elements are collapsed into lists) and validates against a RelaxNG schema string and returns a Qore hash structure.
parseXMLAsDataWithSchema() | parses an XML string as data (duplicate, out-of-order XML elements are collapsed into lists) and validates against an XSD schema string and returns a Qore hash structure.
parseXML() | parses an XML string (XML element order is preserved by appending numeric suffixes to Qore hash key names when necessary) and returns a Qore hash structure.
parseXMLWithRelaxNG() | parses an XML string (XML element order is preserved by appending numeric suffixes to Qore hash key names when necessary) and validates against a RelaxNG schema string and returns a Qore hash structure.
parseXMLWithSchema() | parses an XML string (XML element order is preserved by appending numeric suffixes to Qore hash key names when necessary) and validates against an XSD schema string and returns a Qore hash structure.

Classes Providing XML Functionality

Class | Description
Qore::Xml::XmlDoc | For analyzing and manipulating XML documents.
Qore::Xml::XmlNode | Gives information about XML data in an XML document.
Qore::Xml::XmlReader | For parsing or iterating through the elements of an XML document.

# XML-RPC

XML-RPC is a lightweight but powerful XML over HTTP web service protocol. The xml module includes builtin support for this protocol as described here. You can find more information about XML-RPC, including specifications and examples at http://xmlrpc.org.

Information about Qore's XML-RPC serialization can be found below.

XML-RPC Serialization in Qore

Qore Type | XML-RPC Type | Description
`string` | `string` | direct conversion to UTF-8 string
`integer` | `i4` or `string` | If the integer requires more than 32 bits to represent, then it is sent as a string
`float` | `double` | direct conversion
`number` | `double` | conversion to a double for serialization
`boolean` | `boolean` | direct conversion
`date` | `iso8601` | Absolute date/time values will convert to the default time zone for the calling context for the output string if necessary. Note that relative date/time values (durations) will be serialized with the same format as absolute date/time values.
`binary` | `base64` | direct conversion
`list` | `array` | direct conversion
`hash` | `struct` | direct conversion
all others | n/a | All other types will cause an `XML-RPC-SERIALIZATION-ERROR` to be raised.

Classes Providing XML-RPC Functionality

Class | Description
Qore::Xml::XmlRpcClient | For communicating with XML-RPC servers

Functions Providing XML-RPC Functionality

Function Name | Description
makeFormattedXMLRPCCallString() | Serializes a hash into an XML string formatted for an XML-RPC call with formatting.
makeFormattedXMLRPCCallStringArgs() | Serializes a hash into an XML string formatted for an XML-RPC call with formatting, taking a single list argument for the argument list.
makeFormattedXMLRPCCallStringWithEncoding() | Serializes a hash into an XML string formatted for an XML-RPC call with formatting and an explicit output encoding
makeFormattedXMLRPCCallStringArgsWithEncoding() | Serializes a hash into an XML string formatted for an XML-RPC call with formatting, taking a single list argument for the argument list and an explicit output encoding
makeFormattedXMLRPCFaultResponseString() | Serializes a hash into an XML string formatted for an XML-RPC fault response with formatting.
makeFormattedXMLRPCFaultResponseStringWithEncoding() | Serializes a hash into an XML string formatted for an XML-RPC fault response with formatting and an explicit output encoding.
makeFormattedXMLRPCResponseString() | Serializes a hash into an XML string formatted for an XML-RPC response with formatting.
makeFormattedXMLRPCResponseStringWithEncoding() | Serializes a hash into an XML string formatted for an XML-RPC response with formatting and an explicit output encoding.
makeFormattedXMLRPCValueString() | Serializes a hash into an XML string in XML-RPC value format with formatting.
makeXMLRPCCallString() | Serializes a hash into an XML string formatted for an XML-RPC call without formatting.
makeXMLRPCCallStringArgs() | Serializes a hash into an XML string formatted for an XML-RPC call without formatting, taking a single list argument for the argument list.
makeXMLRPCCallStringWithEncoding() | Serializes a hash into an XML string formatted for an XML-RPC call without formatting and an explicit output encoding.
makeXMLRPCCallStringArgsWithEncoding() | Serializes a hash into an XML string formatted for an XML-RPC call without formatting, taking a single list argument for the argument list and an explicit output encoding.
makeXMLRPCFaultResponseString() | Serializes a hash into an XML string formatted for an XML-RPC fault response without formatting.
makeXMLRPCFaultResponseStringWithEncoding() | Serializes a hash into an XML string formatted for an XML-RPC fault response without formatting and an explicit output encoding.
makeXMLRPCResponseString() | Serializes a hash into an XML string formatted for an XML-RPC response without formatting.
makeXMLRPCResponseStringWithEncoding() | Serializes a hash into an XML string formatted for an XML-RPC response without formatting and an explicit output encoding.
makeXMLRPCValueString() | Serializes a hash into an XML string in XML-RPC value format without formatting.
parseXMLRPCCall() | deserializies an XML-RPC call string, returning a Qore hash respresenting the call information.
parseXMLRPCResponse() | deserializies an XML-RPC response string, returning a Qore hash respresenting the response information.
parseXMLRPCValue() | deserializies an XML-RPC value tree, returning a Qore hash respresenting the information.

# XML Constants

All constants (and classes and namespaces) provided by this module are created under the Qore namespace (the main namespace for the Qore Programming Language).

# Function and Method Tags

## NOOP

Code with this flag makes no calculations, but rather returns a constant value. This flag is given to function and method variants that return a default value depending on the type of argument(s). When variants with this flag are resolved at parse time, a `"call-with-type-errors"` warning is raised (assuming this warning is enabled), unless `PO_REQUIRE_TYPES` or `PO_STRICT_ARGS` is set. If `PO_REQUIRE_TYPES` or `PO_STRICT_ARGS` is set, then these variants are inaccessible at parse time; resolving to a variant with this flag set at parse time causes an exception to be thrown.

These variants are included for backwards-compatibility with qore prior to version 0.8.0 for functions that would ignore type errors in arguments.

This tag is equal to RUNTIME_NOOP, except no runtime effect is caused by resolving a function or method tagged with `NOOP` at runtime; this tag only affects parse time resolution.

## RUNTIME_NOOP

Code with this flag makes no calculations, but rather returns a constant value. This flag is given to function and method variants that return a default value depending on the type of argument(s). When variants with this flag are resolved at parse time, a `"call-with-type-errors"` warning is raised (assuming this warning is enabled), unless `PO_REQUIRE_TYPES` or `PO_STRICT_ARGS` is set. If `PO_REQUIRE_TYPES` or `PO_STRICT_ARGS` is set, then these variants are inaccessible; resolving to a variant with this flag set at parse time or run time causes an exception to be thrown.

These variants are included for backwards-compatibility with qore prior to version 0.8.0 for functions that would ignore type errors in arguments.

This tag is equal to NOOP, except that `RUNTIME_NOOP` is also enforced at runtime.

## RET_VALUE_ONLY

This flag indicates that the function or method has no side effects; it only returns a value, for example.

This tag is identical to CONSTANT except that functions or methods tagged with `RET_VALUE_ONLY` could throw exceptions.

## CONSTANT

This flag indicates that the function or method has no side effects and does not throw any exceptions.

This tag is identical to RET_VALUE_ONLY except that functions or methods tagged with `CONSTANT` do not throw exceptions.

## DEPRECATED

Code with this flag is deprecated and may be removed in a future version of this module; if a variant with this flag is resolved at parse time, a `"deprecated"` warning is raised (assuming this warning is enabled).

# Release Notes

## xml Module Version 1.2

Changes and Bug Fixes in This Release

- implemented dynamic unbinding of service methods in the SoapHandler module
- fixed bugs in XmlReader::toQore() and XmlReader::toQoreData() for SAX parsing
- implemented enhanced logging for the XmlRpcHandler module
- doc updates

## xml Module Version 1.1

Changes and Bug Fixes in This Release

- fixed internal XMl to Qore processing for extreme cases
- fixed makeFormattedXMLString() to really format the output
- fixed XML-RPC parsing with empty elements in structures
- added additional validation to XML-RPC parsing (checking close elements)
- set the character encoding correctly in the outgoing `"Content-Type"` request header
- added suport for the new arbitrary-precision numeric type introduced with Qore 0.8.6