phpMan > perldoc > RPC::XML

NAME
    RPC::XML - A set of classes for core data, message and XML handling

SYNOPSIS
        use RPC::XML;

        $req = RPC::XML::request->new('fetch_prime_factors',
                                      RPC::XML::int->new(985_120_528));
        ...
        $resp = RPC::XML::ParserFactory->new()->parse(STREAM);
        if (ref($resp))
        {
            return $resp->value->value;
        }
        else
        {
            die $resp;
        }

DESCRIPTION
    The RPC::XML package is an implementation of the XML-RPC standard. The package as a whole
    provides classes for data, for clients, for servers and for parsers (based on the XML::Parser
    and XML::LibXML packages from CPAN).

    This module provides a set of classes for creating values to pass to the constructors for
    requests and responses. These are lightweight objects, most of which are implemented as blessed
    scalar references so as to associate specific type information with the value. Classes are also
    provided for requests, responses and faults (errors).

    This module does not actually provide any transport implementation or server basis. For these,
    see RPC::XML::Client and RPC::XML::Server, respectively.

SUBROUTINES/METHODS
    At present, two subroutines are available for import. They must be explicitly imported as part
    of the "use" statement, or with a direct call to "import":

    time2iso8601([$time])
        Convert the integer time value in $time (which defaults to calling the built-in "time" if
        not present) to a (pseudo) ISO 8601 string in the UTC time zone. This is a convenience
        function for occassions when the return value needs to be of the dateTime.iso8601 type, but
        the value on hand is the return from the "time" built-in. Note that the format of this
        string is not strictly compliant with ISO 8601 due to the way the dateTime.iso8601 data-type
        was defined in the specification. See "DATES AND TIMES", below.

    smart_encode(@args)
        Converts the passed-in arguments to datatype objects. Any that are already encoded as such
        are passed through unchanged. The routine is called recursively on hash and array
        references. Note that this routine can only deduce a certain degree of detail about the
        values passed. Boolean values will be wrongly encoded as integers. Pretty much anything not
        specifically recognizable will get encoded as a string object. Thus, for types such as
        "fault", the ISO time value, base-64 data, etc., the program must still explicitly encode
        it. However, this routine will hopefully simplify things a little bit for a majority of the
        usage cases.

        If an argument is a blessed reference (an object), smart_encode will generally treat it as a
        non-blessed reference of the underlying type. That is, objects based on hash references will
        be encoded as if they are unblessed hash references (becoming RPC::XML::struct objects),
        objects based on array references are encoded as array references (RPC::XML::array), etc.
        Only hash references, array references and scalar references are treated in this fashion;
        any other blessed references cannot be down-graded and will cause an exception to be thrown.

        The exception to this are objects of the DateTime class: this package does not utilize
        DateTime directly, but if you pass in a reference to an existing object of that class, it is
        properly converted to an object of the RPC::XML::datetime_iso8601 class.

    In addition to these, the following "helper" functions are also available. They may be imported
    explicitly, or all may be imported via the tag ":types":

        RPC_BOOLEAN RPC_INT RPC_I4 RPC_I8 RPC_DOUBLE
        RPC_DATETIME_ISO8601 RPC_BASE64 RPC_STRING RPC_NIL

    Each creates a data object of the appropriate type from a single value (or, in the case of
    RPC_NIL, from no value). They are merely short- hand for calling the constructors of the data
    classes directly.

    All of the above (helpers and the first two functions) may be imported via the tag ":all".

CLASSES
    The classes provided by this module are broken into two groups: *data* classes and *message*
    classes.

  Data Classes
    The following data classes are provided by this library. Each of these provide at least the set
    of methods below. Note that these classes are designed to create throw-away objects. There is
    currently no mechanism for changing the value stored within one of these object after the
    constructor returns. It is assumed that a new object would be created, instead.

    The common methods to all data classes are:

    new($value)
        Constructor. The value passed in is the value to be encapsulated in the new object.

    value
        Returns the value kept in the object. Processes recursively for "array" and "struct"
        objects.

    as_string
        Returns the value as a XML-RPC fragment, with the proper tags, etc.

    serialize($filehandle)
        Send the stringified rendition of the data to the given file handle. This allows messages
        with arbitrarily-large base-64 data within them to be sent without having to hold the entire
        message within process memory.

    length
        Returns the length, in bytes, of the object when serialized into XML. This is used by the
        client and server classes to calculate message length.

    type
        Returns the type of data being stored in an object. The type matches the XML-RPC
        specification, so the normalized form "datetime_iso8601" comes back as "dateTime.iso8601".

    is_fault
        All types except the fault class return false for this. This is to allow consistent testing
        of return values for fault status, without checking for a hash reference with specific keys
        defined.

    The classes themselves are:

    RPC::XML::int
        Creates an integer value. Constructor expects the integer value as an argument.

    RPC::XML::i4
        This is like the "int" class. Note that services written in strictly-typed languages such as
        C, C++ or Java may consider the "i4" and "int" types as distinct and different.

    RPC::XML::i8
        This represents an 8-byte integer, and is not officially supported by the XML-RPC
        specification. This has been added to accommodate services already in use that have chosen
        to add this extension.

    RPC::XML::double
        Creates a floating-point value.

    RPC::XML::string
        Creates an arbitrary string. No special encoding is done to the string (aside from XML
        document encoding, covered later) with the exception of the "<", ">" and "&" characters,
        which are XML-escaped during object creation, and then reverted when the "value" method is
        called.

    RPC::XML::boolean
        Creates a boolean value. The value returned will always be either of 1 or 0, for true or
        false, respectively. When calling the constructor, the program may specify any of: 0, "no",
        "false", 1, "yes", "true".

    RPC::XML::datetime_iso8601
        Creates an instance of the XML-RPC "dateTime.iso8601" type. The specification for ISO 8601
        may be found elsewhere. No processing is done to the data. Note that the XML-RPC
        specification actually got the format of an ISO 8601 date slightly wrong. Because this is
        what is in the published spec, this package produces dates that match the XML-RPC spec, not
        the the ISO 8601 spec. However, it will *read* date-strings in proper ISO 8601 format. See
        "DATES AND TIMES", below.

    RPC::XML::nil
        Creates a "nil" value. The value returned will always be undef. No value should be passed
        when calling the constructor.

        Note that nil is an extension to XML-RPC, which is not supported by all implementations.
        $RPC::XML::ALLOW_NIL must be set to a non-false value before objects of this type can be
        constructed. See "GLOBAL VARIABLES". However, even if $RPC::XML::ALLOW_NIL is set to a false
        value, the parsers will recognize the "<nil />" tag and construct an object.

        In practice, this type is only useful to denote the equivalent of a "void" return value from
        a function. The type itself is not interchangeable with any of the other data-types.

    RPC::XML::base64
        Creates an object that encapsulates a chunk of data that will be treated as base-64 for
        transport purposes. The value may be passed in as either a string or as a scalar reference.
        Additionally, a second (optional) parameter may be passed, that if true identifies the data
        as already base-64 encoded. If so, the data is decoded before storage. The "value" method
        returns decoded data, and the "as_string" method encodes it before stringification.

        Alternately, the constructor may be given an open filehandle argument instead of direct
        data. When this is the case, the data is never read into memory in its entirety, unless the
        "value" or "as_string" methods are called. This allows the manipulation of arbitrarily-large
        Base-64-encoded data chunks. In these cases, the flag (optional second argument) is still
        relevant, but the data is not pre-decoded if it currently exists in an encoded form. It is
        only decoded as needed. Note that the filehandle passed must be open for reading, at least.
        It will not be written to, but it will be read from. The position within the file will be
        preserved between operations.

        Because of this, this class supports a special method called "to_file", that takes one
        argument. The argument may be either an open, writable filehandle or a string. If it is a
        string, "to_file" will attempt to open it as a file and write the *decoded* data to it. If
        the argument is a an open filehandle, the data will be written to it without any pre- or
        post-adjustment of the handle position (nor will it be closed upon completion). This differs
        from the "serialize" method in that it always writes the decoded data (where the other
        always writes encoded data), and in that the XML opening and closing tags are not written.
        The return value of "to_file" is the size of the data written in bytes.

    RPC::XML::array
        Creates an array object. The constructor takes zero or more data-type instances as
        arguments, which are inserted into the array in the order specified. "value" returns an
        array reference of native Perl types. If a non-null value is passed as an argument to
        "value()", then the array reference will contain datatype objects (a shallow rather than
        deep copy).

    RPC::XML::struct
        Creates a struct object, the analogy of a hash table in Perl. The keys are ordinary strings,
        and the values must all be data-type objects. The "value" method returns a hash table
        reference, with native Perl types in the values. Key order is not preserved. Key strings are
        now encoded for special XML characters, so the use of such ("<", ">", etc.) should be
        transparent to the user. If a non-null value is passed as an argument to "value()", then the
        hash reference will contain the datatype objects rather than native Perl data (a shallow vs.
        deep copy, as with the array type above).

        When creating RPC::XML::struct objects, there are two ways to pass the content in for the
        new object: Either an existing hash reference may be passed, or a series of key/value pairs
        may be passed. If a reference is passed, the existing data is copied (the reference is not
        re-blessed), with the values encoded into new objects as needed.

    RPC::XML::fault
        A fault object is a special case of the struct object that checks to ensure that there are
        two keys, "faultCode" and "faultString".

        As a matter of convenience, since the contents of a RPC::XML::fault structure are
        specifically defined, the constructor may be called with exactly two arguments, the first of
        which will be taken as the code, and the second as the string. They will be converted to
        RPC::XML types automatically and stored by the pre-defined key names.

        Also as a matter of convenience, the fault class provides the following accessor methods for
        directly retrieving the integer code and error string from a fault object:

        code
        string

        Both names should be self-explanatory. The values returned are Perl values, not RPC::XML
        class instances.

  Message Classes
    The message classes are used both for constructing messages for outgoing communication as well
    as representing the parsed contents of a received message. Both implement the following methods:

    new This is the constructor method for the two message classes. The response class may have only
        a single value (as a response is currently limited to a single return value), and requests
        may have as many arguments as appropriate. In both cases, the arguments are passed to the
        exported "smart_encode" routine described earlier.

    as_string
        Returns the message object expressed as an XML document. The document will be lacking in
        linebreaks and indention, as it is not targeted for human reading.

    serialize($filehandle)
        Serialize the message to the given file-handle. This avoids creating the entire XML message
        within memory, which may be relevant if there is especially-large Base-64 data within the
        message.

    length
        Returns the total size of the message in bytes, used by the client and server classes to set
        the Content-Length header.

    The two message-object classes are:

    RPC::XML::request
        This creates a request object. A request object expects the first argument to be the name of
        the remote routine being called, and all remaining arguments are the arguments to that
        routine. Request objects have the following methods (besides "new" and "as_string"):

        name
            The name of the remote routine that the request will call.

        args
            Returns a list reference with the arguments that will be passed. No arguments will
            result in a reference to an empty list.

    RPC::XML::response
        The response object is much like the request object in most ways. It may take only one
        argument, as that is all the specification allows for in a response. Responses have the
        following methods (in addition to "new" and "as_string"):

        value
            The value the response is returning. It will be a RPC::XML data-type.

        is_fault
            A boolean test whether or not the response is signalling a fault. This is the same as
            taking the "value" method return value and testing it, but is provided for clarity and
            simplicity.

DATES AND TIMES
    The XML-RPC specification refers to the date/time values as ISO 8601, but unfortunately got the
    syntax slightly wrong in the examples. However, since this is the published specification it is
    necessary to produce time-stamps that conform to this format. The specification implies that the
    only format for date/time values is:

        YYYYMMDDThh:mm:ss

    (Here, the "T" is literal, the rest represent elements of the date and time.) However, the ISO
    8601 specification does not allow this particular format, and in generally is *considerably*
    more flexible than this. Yet there are implementations of the XML-RPC standard in other
    languages that rely on a strict interpretation of this format.

    To accommodate this, the RPC::XML package only produces dateTime.iso8601 values in the format
    given in the spec, with the possible addition of timezone information if the string used to
    create a RPC::XML::datetime_iso8601 instance included a timezone offset. The string passed in to
    the constructor for that class must match:

        \d\d\d\d-?\d\d-?\d\dT?\d\d:\d\d:\d\d([.,]\d+)?(Z|[-+]\d\d:\d\d)?

    This pattern is also used by smart_encode to distinguish a date/time string from a regular
    string. Note that the "T" is optional here, as it is in the ISO 8601 spec. The timezone is
    optional, and if it is not given then UTC is assumed. The XML-RPC specification says not to
    assume anything about the timezone in the absence of one, but the format of ISO 8601 declares
    that that absence of an explicit timezone dictates UTC.

    If you have DateTime::Format::ISO8601 installed, then RPC::XML::datetime_iso8601 will fall back
    on it to try and parse any input strings that do not match the above pattern. If the string
    cannot be parsed by the DateTime::Format::ISO8601 module, then the constructor returns undef and
    $RPC::XML::ERROR is set.

DIAGNOSTICS
    All constructors (in all data classes) return "undef" upon failure, with the error message
    available in the package-global variable $RPC::XML::ERROR.

GLOBAL VARIABLES
    The following global variables may be changed to control certain behavior of the library. All
    variables listed below may be imported into the application namespace when you "use" RPC::XML:

    $ENCODING
        This variable controls the character-set encoding reported in outgoing XML messages. It
        defaults to "us-ascii", but may be set to any value recognized by XML parsers.

    $FORCE_STRING_ENCODING
        By default, "smart_encode" uses heuristics to determine what encoding is required for a data
        type. For example, 123 would be encoded as "int", where 3.14 would be encoded as "double".
        In some situations it may be handy to turn off all these heuristics, and force encoding of
        "string" on all data types encountered during encoding. Setting this flag to "true" will do
        just that.

        Defaults to "false".

    $ALLOW_NIL
        By default, the XML-RPC "nil" extension is not supported. Set this to a non-false value to
        allow use of nil values. Data objects that are "nil" are represented as undef by Perl. See
        "The nil Datatype".

CAVEATS
    This began as a reference implementation in which clarity of process and readability of the code
    took precedence over general efficiency. It is now being maintained as production code, but may
    still have parts that could be written more efficiently.

BUGS
    Please report any bugs or feature requests to "bug-rpc-xml at rt.cpan.org", or through the web
    interface at <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=RPC-XML>. I will be notified, and
    then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT
    *   RT: CPAN's request tracker

        <http://rt.cpan.org/NoAuth/Bugs.html?Dist=RPC-XML>

    *   AnnoCPAN: Annotated CPAN documentation

        <http://annocpan.org/dist/RPC-XML>

    *   CPAN Ratings

        <http://cpanratings.perl.org/d/RPC-XML>

    *   Search CPAN

        <http://search.cpan.org/dist/RPC-XML>

    *   MetaCPAN

        <https://metacpan.org/release/RPC-XML>

    *   Source code on GitHub

        <http://github.com/rjray/rpc-xml>

LICENSE AND COPYRIGHT
    This file and the code within are copyright (c) 2011 by Randy J. Ray.

    Copying and distribution are permitted under the terms of the Artistic License 2.0
    (<http://www.opensource.org/licenses/artistic-license-2.0.php>) or the GNU LGPL 2.1
    (<http://www.opensource.org/licenses/lgpl-2.1.php>).

CREDITS
    The XML-RPC standard is Copyright (c) 1998-2001, UserLand Software, Inc. See
    <http://www.xmlrpc.com> for more information about the XML-RPC specification.

SEE ALSO
    RPC::XML::Client, RPC::XML::Server

AUTHOR
    Randy J. Ray <rjray AT blackperl.com>