XmlRpcIntrospection: xmlrpcintrospection.py

# -*- coding: utf-8 -*-

__authors__ = ["Sylvain Hellegouarch (sh@defuze.org)"]
__version__ = "1.0"
__date__ = "2005/11/04"
__copyright__ = """
Copyright (c) 2005, Sylvain Hellegouarch
All rights reserved.
"""
__license__ = """
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

     * Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.
     * Redistributions in binary form must reproduce the above copyright notice,
       this list of conditions and the following disclaimer in the documentation
       and/or other materials provided with the distribution.
     * Neither the name of Sylvain Hellegouarch nor the names of his contributors
       may be used to endorse or promote products derived from this software
       without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""

__doc__ = """
Defines some introspection function for a XML-RPC server application handled by CherryPy
Please find at the bottom an example of this class
"""

import inspect
import string

class XmlRpcSystemInformation:
    """
    Defines some introspection function for an XML-RPC server application handled by CherryPy
    See: http://docs.python.org/lib/serverproxy-objects.html
    
    """
    def __init__(self):
        self.rpcmethods = {}

    def _cpOnError(self):
        # We make sure that the errors we explicitely raise
        # are not handled by the default CP error handler
        import sys
        error_type = sys.exc_info()[0]
        if error_type in (LookupError, ValueError):
            return
        # default CP error handler...
        cherrypy.HTTPError(500).set_response()
    
    def register_class(self, classInstance, instancePath=None):
        """
        Registers the given class exposed methods
        
        Keyword arguments:
        classInstance -- class instance which will be scanned for exposed methods
        instancePath -- sets the path to the instance (eg: obj1.obj2 for obj1.obj2.methodName)

        """
        for method in inspect.getmembers(classInstance, inspect.ismethod):
            if getattr(method[1], 'exposed', False) == True:
                if instancePath:
                    self.rpcmethods[instancePath + '.' + method[0]] = method[1]
                else:
                    self.rpcmethods[method[0]] = method[1]

    def listMethods(self):
        """
        Returns a list of all methods callable on the RPC server
        
        """
        return self.rpcmethods.keys()
    listMethods.exposed = True

    def methodHelp(self, methodName):
        """
        Returns the doc string of the method in parameter.
        If none available returns a default message.

        Keyword arguments:
        methodName -- name of the method to look up
        
        """
        method = None
        if methodName not in self.rpcmethods.keys():
            raise LookupError, "This method is not registered on this server"

        method = self.rpcmethods[methodName]
            
        doc = method.__doc__
        if not doc:
            raise ValueError, 'No available help for ' + methodName
        return doc
    methodHelp.exposed = True

if __name__ == '__main__':
    import cherrypy
    
    class A:
        def hello(self):
            return "hello there from A"
        hello.exposed = True

    class B:
        def hello(self):
            return "hello there from B"
        hello.exposed = True
        
    class Root:
        def echo(self, value=''):
            """
            Return the value passed in parameters

            Keyword arguments:
            value -- the token to echo back (default '')

            """
            return value
        echo.exposed = True

    # Let's build the tree of exposed objects
    cherrypy.root = Root()
    cherrypy.root.a = A()
    cherrypy.root.a.b = B()

    # Attach each exposed object (part of the XML-RPC application)
    # to the object dealing with introspection
    system = XmlRpcSystemInformation()
    system.register_class(cherrypy.root)
    system.register_class(cherrypy.root.a, 'a')
    system.register_class(cherrypy.root.a.b, 'a.b')
    
    cherrypy.root.system = system
    
    cherrypy.config.update({'global': { 'xmlRpcFilter.on':True,
                                        'server.socketPort': 8080 }})

    cherrypy.server.start()

    # Your client could then try:
##     import xmlrpclib
##     server = xmlrpclib.ServerProxy('http://localhost:8080/')
##     server.system.listMethods() # will return ['a.hello', 'a.b.hello', 'echo']
##     server.system.methodHelp('echo') # will return the help for echo
##     server.system.methodHelp('a.b.hello') # will raise xmlrpclib.Fault: 'No available help for a.b.hello'
##     server.system.methodHelp('ech') # will raise xmlrpclib.Fault because cho doesn't exist
##     server.system.methodHelp() # will raise a xmlrpclib.ProtocolError because methodHelp takes at least one arg