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XML-RPC for Common Lisp

branch: master
README.md

CXML-RPC: An xml-rpc library for Common Lisp

This library implements xml-rpc client and server functionality using Drakma, CXML and Hunchentoot.

Installation

Get it via git:

git clone http://github.com/antifuchs/cxml-rpc

Then adjust your ASDF to find cxml-rpc.asd. After that,

(asdf:oos 'asdf:load-op :cxml-rpc)

Usage

An XML-RPC Client

Acting as an XML-RPC client is pretty easy: Just call the functions on the endpoints you need. The function's first return value is the value returned by the server, and the second return value is its type.

* (xrpc:call "http://betty.userland.com/RPC2" "examples.getStateName" '(:integer 41))
"South Dakota"
:STRING
Argument passing

Since the mapping of CL types to XML-RPC types is not easily DWIM-able, you need to pass args with explicit type hints. CXML-RPC maps these types (as keywords):

  • :boolean - generalized boolean
  • :integer - 4-octet integers
  • :double - floating-point doubles
  • :string - strings
  • :time - universal times as CL integers
  • :base64 - strings, file streams or vectors containing (unsigned-byte 8) elements.
  • :struct - alists
  • :array - sequences

An XML-RPC Server

You can run multiple XML RPC handlers in your hunchentoot instance: These are identified by a handler tag that you can choose. This tag is not exposed to the outside world, so you can run multiple sites (or endpoints) with a different set of xml-rpc methods in the same lisp image.

Step one: Teach hunchentoot about your handler.

(push 
     (hunchentoot:create-prefix-dispatcher "/RPC2" 
                                           (cxml:cxml-rpc-method-handler 'some-tag))
     hunchentoot:*dispatch-table*)

This tells hunchentoot to dispatch xml-rpc calls on /RPC2 to dispatch xml-rpc methods. This handler will serve only methods that are defined with the group tag some-tag.

Step two: Define methods.

Define-xrpc-method is what you use to create a function that can be called from xml-rpc. Its arguments are:

  1. The function name and handler group (following the example above, that should be some-tag),
  2. a list of argument variables,
  3. a type signature: First the return type, then the parameter types,
  4. an optional docstring.

CXML-RPC allows introspection via the system.getCapabilities, system.listMethods, system.methodHelp, and system.methodSignature.

(define-xrpc-method (add some-tag) (a b) (:integer :integer :integer)
  "Add two numbers"
  (+ a b))
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