# xmlrpc4r - HOWTO

Copyright (C) 2001, 2002 by Michael Neumann (neumann@s-direktnet.de)

Released under the same term of license as Ruby.

# Install

You can currently use xmlrpc4r with two parsers, XMLParser and/or NQXML. Both are available at RAA (Ruby Application Archive - <URL:http://www.ruby-lang.org/en/raa.html>).

If you want to use XMLParser (Expat Module for Ruby), you have to install James Clark's XML Parser Toolkit "expat". I recommend using XMLParser, because xmlrpc4r is better tested with it and XMLParser is much faster than NQXML. The advantage of using NQXML is that it is written in pure Ruby.

Then you'll need "xmlrpc4r" of course, which is available at <URL:http://www.fantasy-coders.de/ruby/xmlrpc4r>.

To install xmlrpc4r:

    tar -xvzf xmlrpc4r-1_7_4.tar.gz
    cd xmlrpc4r-1_7_4
    su root -c "ruby install.rb"

# Samples

## Client

    require "xmlrpc/client"

    # Make an object to represent the XML-RPC server.
    server = XMLRPC::Client.new( "xmlrpc-c.sourceforge.net", "/api/sample.php")

    # Call the remote server and get our result
    result = server.call("sample.sumAndDifference", 5, 3)

    sum = result["sum"]
    difference = result["difference"]

    puts "Sum: #{sum}, Difference: #{difference}"

## Client with XML-RPC fault-structure handling

There are two possible ways, of handling a fault-structure:

### by catching a XMLRPC::FaultException exception

    require "xmlrpc/client"

    # Make an object to represent the XML-RPC server.
    server = XMLRPC::Client.new( "xmlrpc-c.sourceforge.net", "/api/sample.php")

    begin
      # Call the remote server and get our result
      result = server.call("sample.sumAndDifference", 5, 3)

      sum = result["sum"]
      difference = result["difference"]

      puts "Sum: #{sum}, Difference: #{difference}"

    rescue XMLRPC::FaultException => e
      puts "Error: "
      puts e.faultCode
      puts e.faultString
    end

### by calling "call2" which returns a boolean

    require "xmlrpc/client"

    # Make an object to represent the XML-RPC server.
    server = XMLRPC::Client.new( "xmlrpc-c.sourceforge.net", "/api/sample.php")

    # Call the remote server and get our result
    ok, result = server.call2("sample.sumAndDifference", 5, 3)

    if ok
      sum = result["sum"]
      difference = result["difference"]

      puts "Sum: #{sum}, Difference: #{difference}"
    else
      puts "Error: "
      puts result.faultCode
      puts result.faultString
    end

## Client using Proxy

You can create a `Proxy` object onto which you can call methods. This way it looks nicer. Both forms, "call" and "call2" are supported through "proxy" and "proxy2". You can additionally give arguments to the Proxy, which will be given to each XML-RPC call using that Proxy.

    require "xmlrpc/client"

    # Make an object to represent the XML-RPC server.
    server = XMLRPC::Client.new( "xmlrpc-c.sourceforge.net", "/api/sample.php")

    # Create a Proxy object
    sample = server.proxy("sample")

    # Call the remote server and get our result
    result = sample.sumAndDifference(5,3)

    sum = result["sum"]
    difference = result["difference"]

    puts "Sum: #{sum}, Difference: #{difference}"

## CGI-based Server

There are also two ways to define handler, the first is like C/PHP, the second like Java, of course both ways can be mixed:

### C/PHP-like (handler functions)

    require "xmlrpc/server"

    s = XMLRPC::CGIServer.new

    s.add_hanlder("sample.sumAndDifference") do |a,b|
      { "sum" => a + b, "difference" => a - b }
    end

    s.serve

### Java-like (handler classes)

    require "xmlrpc/server"

    s = XMLRPC::CGIServer.new

    class MyHandler
      def sumAndDifference(a, b)
        { "sum" => a + b, "difference" => a - b }
      end
    end

    s.add_handler("sample", MyHandler.new)
    s.serve

To return a fault-structre you have to raise an FaultException e.g.:

    raise XMLRPC::FaultException.new(3, "division by Zero")

## Standalone server

Same as CGI-based server, only that the line

    server = XMLRPC::CGIServer.new

must be changed to

    server = XMLRPC::Server.new(8080)

if you want a server listening on port 8080. The rest is the same.

## Choosing a different XML Parser or XML Writer

The examples above all use the default parser (which is now since 1.6.9 NQXMLParser) and a default XML writer. If you want to use XMLParser or XMLStreamParser, then you have to call the `#set_parser` method onto `XMLRPC::Client` instances or instances of subclasses of `XMLRPC::BasicServer` or by editing lib/config.rb.

Client Example:

    # ...
    server = XMLRPC::Client.new( "xmlrpc-c.sourceforge.net", "/api/sample.php")
    server.set_parser(XMLRPC::XMLParser::XMLParser.new)
    # ...

Server Example:

    # ...
    s = XMLRPC::CGIServer.new
    s.set_parser(XMLRPC::XMLParser::XMLStreamParser.new)
    # ...

or:

    # ...
    server = XMLRPC::Server.new(8080)
    server.set_parser(XMLRPC::XMLParser::NQXMLParser.new)
    # ...

Note that XMLStreamParser is incredible faster (and uses less memory) than XMLTreeParser, NQXMLStreamParser or NQXMLTreeParser, and scales well for large documents. For example for a 0.5 MB XML document with many tags, XMLStreamParser is ~350 (!) times faster than NQXMLTreeParser and still ~18 times as fast as XMLTreeParser.

You can change the XML Writer by calling `#set_writer`.

    Much easier is (when using xmlrpc4r version > 1.6.3) to change
    the file xmlrpc/config.rb and change there the settings which
    XML parser/writer to use.

# History

    $Id: howto.rd,v 1.16 2002/01/08 23:00:51 michael Exp $