make_method(1)
NAME
make_method - Turn Perl code into an XML description for
RPC::XML::Server
SYNOPSIS
make_method --name=system.identification --helptext='System ID string'
--signature=string --code=ident.pl --output=ident.xpl
make_method --base=methods/identification
DESCRIPTION
This is a simple tool to create the XML descriptive files for specify-
ing methods to be published by an RPC::XML::Server-based server.
If a server is written such that the methods it exports (or publishes)
are a part of the running code, then there is no need for this tool.
However, in cases where the server may be separate and distinct from
the code (such as an Apache-based RPC server), specifying the routines
and filling in the supporting information can be cumbersome.
One solution that the RPC::XML::Server package offers is the means to
load publishable code from an external file. The file is in a simple
XML dialect that clearly delinates the externally-visible name, the
method signatures, the help text and the code itself. These files may
be created manually, or this tool may be used as an aide.
OPTIONS
The tool recognizes the following options:
--help
Prints a short summary of the options.
--name=STRING
Specifies the published name of the method being encoded. This is
the name by which it will be visible to clients of the server.
--type=STRING
Specify the type for the resulting file. "Type" here refers to
whether the container tag used in the resulting XML will specify a
procedure or a method. The default is method. The string is treated
case-independant, and only the first character ("m" or "p") is
actually regarded.
--version=STRING
Specify a version stamp for the code routine.
--hidden
If this is passe, the resulting file will include a tag that tells
the server daemon to not make the routine visible through any
introspection interfaces.
--signature=STRING [ --signature=STRING ... ]
Specify one or more signatures for the method. Signatures should be
the type names as laid out in the documentation in RPC::XML, with
the elements separated by a colon. You may also separate them with
spaces, if you quote the argument. This option may be specified
more than once, as some methods may have several signatures.
--helptext=STRING
Specify the help text for the method as a simple string on the com-
mand line. Not suited for terribly long help strings.
--helpfile=FILE
Read the help text for the method from the file specified.
--code=FILE
Read the actual code for the routine from the file specifed. If
this option is not given, the code is read from the standard input
file descriptor.
--output=FILE
Write the resulting XML representation to the specified file. If
this option is not given, then the output goes to the standard out-
put file descriptor.
--base=NAME
This is a special, "all-in-one" option. If passed, all other
options are ignored.
The value is used as the base element for reading information from
a file named BASE.base. This file will contain specification of the
name, version, hidden status, signatures and other method informa-
tion. Each line of the file should look like one of the following:
Name: SSTTRRIINNGG
Specify the name of the routine being published. If this line
does not appear, then the value of the --base argument with all
directory elements removed will be used.
Version: SSTTRRIINNGG
Provide a version stamp for the function. If no line matching
this pattern is present, no version tag will be written.
Hidden: SSTTRRIINNGG
If present, STRING should be either "yes" or "no" (case not
important). If it is "yes", then the method is marked to be
hidden from any introspection API.
Signature: SSTTRRIINNGG
This line may appear more than once, and is treated cumula-
tively. Other options override previous values if they appear
more than once. The portion following the "Signature:" part is
taken to be a published signature for the method, with elements
separated by whitespace. Each method must have at least one
signature, so a lack of any will cause an error.
Helpfile: SSTTRRIINNGG
Specifies the file from which to read the help text. It is not
an error if no help text is specified.
Codefile: SSTTRRIINNGG
Specifies the file from which to read the code. Code is assumed
to be Perl, and will be tagged as such in the resulting file.
Codefile[lang]: ssttrriinngg
Specifies the file from which to read code, while also identi-
fying the language that the code is in. This allows for the
creation of a XPL file that includes multiple language imple-
mentations of the given method or procedure.
Any other lines than the above patterns are ignored.
If no code has been read, then the tool will exit with an error
message.
The output is written to BASE.xpl, preserving the path information
so that the resulting file is right alongside the source files.
This allows constructs such as:
make_method --base=methods/introspection
FILE FORMAT AND DTD
The file format for these published routines is a very simple XML
dialect. This is less due to XML being an ideal format than it is the
availability of the parser, given that the RPC::XML::Server class will
already have the parser code in core. Writing a completely new format
would not have gained anything.
The Document Type Declaration for the format can be summarized by:
<!ELEMENT proceduredef (name, version?, hidden?, signature+,
help?, code)>
<!ELEMENT methoddef (name, version?, hidden?, signature+,
help?, code)>
<!ELEMENT functiondef (name, version?, hidden?, signature+,
help?, code)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT version (#PCDATA)>
<!ELEMENT hidden EMPTY>
<!ELEMENT signature (#PCDATA)>
<!ELEMENT help (#PCDATA)>
<!ELEMENT code (#PCDATA)>
<!ATTLIST code language (#PCDATA)>
The file "rpc-method.dtd" that comes with the distribution has some
commentary in addition to the actual specification.
A file is (for now) limited to one definition. This is started by the
one of the opening tags "<methoddef>", "<functiondef>" or "<procedure-
def>". This is followed by exactly one "<name>" container specifying
the method name, an optional version stamp, an optional hide-from-
introspection flag, one or more "<signature>" containers specifying
signatures, an optional "<help>" container with the help text, then the
"<code>" container with the actual program code. All text should use
entity encoding for the symbols:
& C<&> (ampersand)
E<lt> C<<> (less-than)
E<gt> C<>> (greater-than)
The parsing process within the server class will decode the entities.
To make things easier, the tool scans all text elements and encodes the
above entities before writing the file.
The Specification of Code
This is not "Programming 101", nor is it "Perl for the Somewhat Dim".
The code that is passed in via one of the "*.xpl" files gets passed to
"eval" with next to no modification (see below). Thus, badly-written or
malicious code can very well wreak havoc on your server. This is not
the fault of the server code. The price of the flexibility this system
offers is the responsibility on the part of the developer to ensure
that the code is tested and safe.
Code itself is treated as verbatim as possible. Some edits may occur on
the server-side, as it make the code suitable for creating an anonymous
subroutine from. The make_method tool will attempt to use a "CDATA"
section to embed the code within the XML document, so that there is no
need to encode entities or such. This allows for the resulting *.xpl
files to be syntax-testable with "perl -cx". You can aid this by ensur-
ing that the code does not contain either of the two following charac-
ter sequences:
]]>
__DATA__
The first is the "CDATA" terminator. If it occurs naturally in the
code, it would trigger the end-of-section in the parser. The second is
the familiar Perl token, which is inserted so that the remainder of the
XML document does not clutter up the Perl parser.
EXAMPLES
The RPC::XML distribution comes with a number of default methods in a
subdirectory called (cryptically enough) "methods". Each of these is
expressed as a set of ("*.base", "*.code", "*.help") files. The Make-
file.PL file configures the resulting Makefile such that these are used
to create "*.xpl" files using this tool, and then install them.
DIAGNOSTICS
Most problems come out in the form of error messages followed by an
abrupt exit.
CAVEATS
I don't much like this approach to specifying the methods, but I liked
my other ideas even less.
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.
LICENSE
This module is licensed under the terms of the Artistic License that
covers Perl itself. See <http://www.opensource.org/licenses/artis-
tic-license.php> for the license itself.
SEE ALSO
RPC::XML, RPC::XML::Server
AUTHOR
Randy J. Ray <rjray@blackperl.com>
perl v5.8.8 2004-12-09 MAKE_METHOD(1)
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