xmlrpc.client —- XML-RPC client access

源代码:Lib/xmlrpc/client.py

XML-RPC is a Remote Procedure Call method that uses XML passed via HTTP(S) as atransport. With it, a client can call methods with parameters on a remoteserver (the server is named by a URI) and get back structured data. This modulesupports writing XML-RPC client code; it handles all the details of translatingbetween conformable Python objects and XML on the wire.

警告

The xmlrpc.client module is not secure against maliciouslyconstructed data. If you need to parse untrusted or unauthenticated data seeXML 漏洞.

在 3.5 版更改: For HTTPS URIs, xmlrpc.client now performs all the necessarycertificate and hostname checks by default.

• class xmlrpc.client.ServerProxy(uri, transport=None, encoding=None, verbose=False, allow_none=False, use_datetime=False, use_builtin_types=False, *, headers=(), context=None)
• A ServerProxy instance is an object that manages communication with aremote XML-RPC server. The required first argument is a URI (Uniform ResourceIndicator), and will normally be the URL of the server. The optional secondargument is a transport factory instance; by default it is an internalSafeTransport instance for https: URLs and an internal HTTPTransport instance otherwise. The optional third argument is anencoding, by default UTF-8. The optional fourth argument is a debugging flag.

The following parameters govern the use of the returned proxy instance.If allow_none is true, the Python constant None will be translated intoXML; the default behaviour is for None to raise a TypeError. This isa commonly-used extension to the XML-RPC specification, but isn't supported byall clients and servers; see http://ontosys.com/xml-rpc/extensions.phpfor a description.The use_builtin_types flag can be used to cause date/time valuesto be presented as datetime.datetime objects and binary data to bepresented as bytes objects; this flag is false by default.datetime.datetime, bytes and bytearray objectsmay be passed to calls.The headers parameter is an optional sequence of HTTP headers to send witheach request, expressed as a sequence of 2-tuples representing the headername and value. (e.g. [('Header-Name', 'value')]).The obsolete use_datetime flag is similar to use_builtin_types but itapplies only to date/time values.

在 3.3 版更改: The use_builtin_types flag was added.

在 3.8 版更改: The headers parameter was added.

Both the HTTP and HTTPS transports support the URL syntax extension for HTTPBasic Authentication: http://user:pass@host:port/path. The user:passportion will be base64-encoded as an HTTP 'Authorization' header, and sent tothe remote server as part of the connection process when invoking an XML-RPCmethod. You only need to use this if the remote server requires a BasicAuthentication user and password. If an HTTPS URL is provided, context maybe ssl.SSLContext and configures the SSL settings of the underlyingHTTPS connection.

The returned instance is a proxy object with methods that can be used to invokecorresponding RPC calls on the remote server. If the remote server supports theintrospection API, the proxy can also be used to query the remote server for themethods it supports (service discovery) and fetch other server-associatedmetadata.

Types that are conformable (e.g. that can be marshalled through XML),include the following (and except where noted, they are unmarshalledas the same Python type):

This is the full set of data types supported by XML-RPC. Method calls may alsoraise a special Fault instance, used to signal XML-RPC server errors, orProtocolError used to signal an error in the HTTP/HTTPS transport layer.Both Fault and ProtocolError derive from a base class calledError. Note that the xmlrpc client module currently does not marshalinstances of subclasses of built-in types.

When passing strings, characters special to XML such as <, >, and &will be automatically escaped. However, it's the caller's responsibility toensure that the string is free of characters that aren't allowed in XML, such asthe control characters with ASCII values between 0 and 31 (except, of course,tab, newline and carriage return); failing to do this will result in an XML-RPCrequest that isn't well-formed XML. If you have to pass arbitrary bytesvia XML-RPC, use bytes or bytearray classes or theBinary wrapper class described below.

Server is retained as an alias for ServerProxy for backwardscompatibility. New code should use ServerProxy.

在 3.5 版更改: Added the context argument.

在 3.6 版更改: Added support of type tags with prefixes (e.g. ex:nil).Added support of unmarshalling additional types used by Apache XML-RPCimplementation for numerics: i1, i2, i8, biginteger,float and bigdecimal.See http://ws.apache.org/xmlrpc/types.html for a description.

参见

• XML-RPC HOWTO

• A good description of XML-RPC operation and client software in several languages.Contains pretty much everything an XML-RPC client developer needs to know.

• XML-RPC Introspection

• Describes the XML-RPC protocol extension for introspection.

• XML-RPC Specification

• The official specification.

• Unofficial XML-RPC Errata

• Fredrik Lundh's "unofficial errata, intended to clarify certaindetails in the XML-RPC specification, as well as hint at'best practices' to use when designing your own XML-RPCimplementations."

ServerProxy 对象

A ServerProxy instance has a method corresponding to each remoteprocedure call accepted by the XML-RPC server. Calling the method performs anRPC, dispatched by both name and argument signature (e.g. the same method namecan be overloaded with multiple argument signatures). The RPC finishes byreturning a value, which may be either returned data in a conformant type or aFault or ProtocolError object indicating an error.

Servers that support the XML introspection API support some common methodsgrouped under the reserved system attribute:

• ServerProxy.system.listMethods()

• This method returns a list of strings, one for each (non-system) methodsupported by the XML-RPC server.

• ServerProxy.system.methodSignature(name)

• This method takes one parameter, the name of a method implemented by the XML-RPCserver. It returns an array of possible signatures for this method. A signatureis an array of types. The first of these types is the return type of the method,the rest are parameters.

Because multiple signatures (ie. overloading) is permitted, this method returnsa list of signatures rather than a singleton.

Signatures themselves are restricted to the top level parameters expected by amethod. For instance if a method expects one array of structs as a parameter,and it returns a string, its signature is simply "string, array". If it expectsthree integers and returns a string, its signature is "string, int, int, int".

If no signature is defined for the method, a non-array value is returned. InPython this means that the type of the returned value will be something otherthan list.

• ServerProxy.system.methodHelp(name)
• This method takes one parameter, the name of a method implemented by the XML-RPCserver. It returns a documentation string describing the use of that method. Ifno such string is available, an empty string is returned. The documentationstring may contain HTML markup.

在 3.5 版更改: Instances of ServerProxy support the context manager protocolfor closing the underlying transport.

A working example follows. The server code:

from xmlrpc.server import SimpleXMLRPCServer
 
def is_even(n):
    return n % 2 == 0
 
server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(is_even, "is_even")
server.serve_forever()

The client code for the preceding server:

import xmlrpc.client
 
with xmlrpc.client.ServerProxy("http://localhost:8000/") as proxy:
    print("3 is even: %s" % str(proxy.is_even(3)))
    print("100 is even: %s" % str(proxy.is_even(100)))

DateTime 对象

• class xmlrpc.client.DateTime

• This class may be initialized with seconds since the epoch, a timetuple, an ISO 8601 time/date string, or a datetime.datetimeinstance. It has the following methods, supported mainly for internaluse by the marshalling/unmarshalling code:

  • decode(string)

  • Accept a string as the instance's new time value.

  • encode(out)

  • Write the XML-RPC encoding of this DateTime item to the out streamobject.

It also supports certain of Python's built-in operators through rich comparisonand repr() methods.

A working example follows. The server code:

import datetime
from xmlrpc.server import SimpleXMLRPCServer
import xmlrpc.client
 
def today():
    today = datetime.datetime.today()
    return xmlrpc.client.DateTime(today)
 
server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(today, "today")
server.serve_forever()

The client code for the preceding server:

import xmlrpc.client
import datetime
 
proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
 
today = proxy.today()
# convert the ISO8601 string to a datetime object
converted = datetime.datetime.strptime(today.value, "%Y%m%dT%H:%M:%S")
print("Today: %s" % converted.strftime("%d.%m.%Y, %H:%M"))

Binary 对象

• class xmlrpc.client.Binary

• This class may be initialized from bytes data (which may include NULs). Theprimary access to the content of a Binary object is provided by anattribute:

  • data
  • The binary data encapsulated by the Binary instance. The data isprovided as a bytes object.

Binary objects have the following methods, supported mainly forinternal use by the marshalling/unmarshalling code:

• decode(bytes)

• Accept a base64 bytes object and decode it as the instance's new data.

• encode(out)

• Write the XML-RPC base 64 encoding of this binary item to the out stream object.

The encoded data will have newlines every 76 characters as perRFC 2045 section 6.8,which was the de facto standard base64 specification when theXML-RPC spec was written.

It also supports certain of Python's built-in operators through eq()and ne() methods.

Example usage of the binary objects. We're going to transfer an image overXMLRPC:

from xmlrpc.server import SimpleXMLRPCServer
import xmlrpc.client
 
def python_logo():
    with open("python_logo.jpg", "rb") as handle:
        return xmlrpc.client.Binary(handle.read())
 
server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(python_logo, 'python_logo')
 
server.serve_forever()

The client gets the image and saves it to a file:

import xmlrpc.client
 
proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
with open("fetched_python_logo.jpg", "wb") as handle:
    handle.write(proxy.python_logo().data)

Fault 对象

• class xmlrpc.client.Fault

• A Fault object encapsulates the content of an XML-RPC fault tag. Faultobjects have the following attributes:

  • faultCode

  • A string indicating the fault type.

  • faultString

  • A string containing a diagnostic message associated with the fault.

In the following example we're going to intentionally cause a Fault byreturning a complex type object. The server code:

from xmlrpc.server import SimpleXMLRPCServer
 
# A marshalling error is going to occur because we're returning a
# complex number
def add(x, y):
    return x+y+0j
 
server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(add, 'add')
 
server.serve_forever()

The client code for the preceding server:

import xmlrpc.client
 
proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
try:
    proxy.add(2, 5)
except xmlrpc.client.Fault as err:
    print("A fault occurred")
    print("Fault code: %d" % err.faultCode)
    print("Fault string: %s" % err.faultString)

ProtocolError 对象

• class xmlrpc.client.ProtocolError

• A ProtocolError object describes a protocol error in the underlyingtransport layer (such as a 404 'not found' error if the server named by the URIdoes not exist). It has the following attributes:

  • url

  • The URI or URL that triggered the error.

  • errcode

  • The error code.

  • errmsg

  • The error message or diagnostic string.

  • headers

  • A dict containing the headers of the HTTP/HTTPS request that triggered theerror.

In the following example we're going to intentionally cause a ProtocolErrorby providing an invalid URI:

import xmlrpc.client
 
# create a ServerProxy with a URI that doesn't respond to XMLRPC requests
proxy = xmlrpc.client.ServerProxy("http://google.com/")
 
try:
    proxy.some_method()
except xmlrpc.client.ProtocolError as err:
    print("A protocol error occurred")
    print("URL: %s" % err.url)
    print("HTTP/HTTPS headers: %s" % err.headers)
    print("Error code: %d" % err.errcode)
    print("Error message: %s" % err.errmsg)

MultiCall 对象

The MultiCall object provides a way to encapsulate multiple calls to aremote server into a single request 1.

• class xmlrpc.client.MultiCall(server)
• Create an object used to boxcar method calls. server is the eventual target ofthe call. Calls can be made to the result object, but they will immediatelyreturn None, and only store the call name and parameters in theMultiCall object. Calling the object itself causes all stored calls tobe transmitted as a single system.multicall request. The result of this callis a generator; iterating over this generator yields the individualresults.

A usage example of this class follows. The server code:

from xmlrpc.server import SimpleXMLRPCServer
 
def add(x, y):
    return x + y
 
def subtract(x, y):
    return x - y
 
def multiply(x, y):
    return x * y
 
def divide(x, y):
    return x // y
 
# A simple server with simple arithmetic functions
server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_multicall_functions()
server.register_function(add, 'add')
server.register_function(subtract, 'subtract')
server.register_function(multiply, 'multiply')
server.register_function(divide, 'divide')
server.serve_forever()

The client code for the preceding server:

import xmlrpc.client
 
proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
multicall = xmlrpc.client.MultiCall(proxy)
multicall.add(7, 3)
multicall.subtract(7, 3)
multicall.multiply(7, 3)
multicall.divide(7, 3)
result = multicall()
 
print("7+3=%d, 7-3=%d, 7*3=%d, 7//3=%d" % tuple(result))

Convenience Functions

• xmlrpc.client.dumps(params, methodname=None, methodresponse=None, encoding=None, allow_none=False)

• Convert params into an XML-RPC request. or into a response if methodresponse_is true. _params can be either a tuple of arguments or an instance of theFault exception class. If methodresponse is true, only a single valuecan be returned, meaning that params must be of length 1. encoding, ifsupplied, is the encoding to use in the generated XML; the default is UTF-8.Python's None value cannot be used in standard XML-RPC; to allow usingit via an extension, provide a true value for allow_none.

• xmlrpc.client.loads(data, use_datetime=False, use_builtin_types=False)

• Convert an XML-RPC request or response into Python objects, a (params,methodname). params is a tuple of argument; methodname is a string, orNone if no method name is present in the packet. If the XML-RPC packetrepresents a fault condition, this function will raise a Fault exception.The use_builtin_types flag can be used to cause date/time values to bepresented as datetime.datetime objects and binary data to bepresented as bytes objects; this flag is false by default.

The obsolete use_datetime flag is similar to use_builtin_types but itapplies only to date/time values.

在 3.3 版更改: The use_builtin_types flag was added.

Example of Client Usage

# simple test program (from the XML-RPC specification)
from xmlrpc.client import ServerProxy, Error
 
# server = ServerProxy("http://localhost:8000") # local server
with ServerProxy("http://betty.userland.com") as proxy:
 
    print(proxy)
 
    try:
        print(proxy.examples.getStateName(41))
    except Error as v:
        print("ERROR", v)

To access an XML-RPC server through a HTTP proxy, you need to define a customtransport. The following example shows how:

import http.client
import xmlrpc.client
 
class ProxiedTransport(xmlrpc.client.Transport):
 
    def set_proxy(self, host, port=None, headers=None):
        self.proxy = host, port
        self.proxy_headers = headers
 
    def make_connection(self, host):
        connection = http.client.HTTPConnection(*self.proxy)
        connection.set_tunnel(host, headers=self.proxy_headers)
        self._connection = host, connection
        return connection
 
transport = ProxiedTransport()
transport.set_proxy('proxy-server', 8080)
server = xmlrpc.client.ServerProxy('http://betty.userland.com', transport=transport)
print(server.examples.getStateName(41))

Example of Client and Server Usage

See SimpleXMLRPCServer Example.

脚注

• 1
• This approach has been first presented in a discussion on xmlrpc.com.