XMLRPC Methods

The XMLRPC Method product provides support for remote procedure calls with the XML-RPC standard. The intent is to create a plug-in replacement for an external method.

Not everything is callable: For instance you can't call title or id on a folder, but you can call title_or_id, title_and_id, getId and getPhysicalPath. Essentially everything that will also work as http://remote.com/folder/title_or_id. The method propertyItems returns an especially complex and interesting result.

You can also do privileged things that requires a login. You simply add the username and password to the remote url the conventional way:

http://username:[email protected]/

Then you can call methods such as document_src on DTML methods etc.

Sending arguments

XMLRPC allows you to send a number of arguments to the remote procedure. These arguments can be integers, strings, lists, dictionaries etc. and combinations hereof.

To test with the XMLRPCLIB example, create a XMLRPC method with the name statelookup, the URL http://betty.userland.com and the method examples.getStateName.

The create a DTML method with the call: <dtml-var "statelookup(5)"> and see what happens.

Sending arguments to remote DTML Methods

Try this: create a DTML method with address /welcome on the remote computer with the two lines:

    <dtml-call "REQUEST.set('res', 'Welcome to ' + place )">
    <dtml-return "REQUEST['res']">

Then on the local computer create an XMLRPC method called querywelcome with the URL http://remote.com/, and a method of welcome.

To call the remote procedure from a DTML Method do:

    <dtml-var "querywelcome( {'place':'my world'}) ">

If the method returns a list or a dictionary, you can use the <dtml-in method mapping>

Calling a Z SQL Method:

You can't do it directly. The Z SQL Method returns objects, so you must use a DTML Method to build a list of dictionaries. Let's assume we have a table with the two columns ISSUE_ID and ISSUE_NAME. Then your DTML Method will look like this:

    <dtml-call "REQUEST.set('result',[])">
    <dtml-in select_all_from_issues>
    <dtml-call "REQUEST['result'].append({'ID': ISSUE_ID, 'NAME':ISSUE_NAME}) ">
    </dtml-in>
    <dtml-return "REQUEST['result']">

Other things to note:

When an object is called via XML-RPC, there's nothing in the REQUEST variable. You can create variables in the namespace, but that's it. Some versions of Zope can't see simple variables. So in the example above you have to write <dtml-return "REQUEST[&apos;result&apos;]"> rather than <dtml-return result> to be one the safe side.

Due to its nature XMLRPC methods can take a long time to execute or not return at all if the remote server is unresponsive. Therefore make use of the timeout value. The timeout functionality is implemented with threads.

Another optimization technique available to you is to cache the results. We have made XMLRPCMethod cacheable with RAMCacheManager.

Bugs

XML-RPC takes only positional parameters. Since arguments given in the QUERY_STRING are keyword arguments as in ?x=1&y=2 it isn't possible to specify arguments in GET or POST statements.

The <dateTime.iso8601> element is difficult to use. It is not converted to a Zope DateTime.

References

Directory of services