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:
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@blackperl.com>