本文講一下如何用python的xmlrpc開服務，進行server/client的通信。
應用場景：1）需多client訪問應用程序給予應答情況——網頁服務； 2）數據極大，希望加載一次，後面只用方法調用
解決方案： 開兩個服務，一個數據服務，一個網絡服務；
數據服務端加載數據，網絡服務端調用數據，並將結果顯示在網絡服務中；
外部調用網絡服務返回結果；
應用工具：xmlrpc，本文中以python 2.7.3的xmlrpclib為例，其他語言也有相應接口
下面分別說明。
1. 數據端
在本地localhost的8000端口開server服務，load數據，並定義接口查找數據第i個元素（findai）.
Server :
from SimpleXMLRPCServer import SimpleXMLRPCServer
global a
def load():
global a
a = [1 ,2, 24]
return a
def findai(i):
global a
print a[i]
return a[i]
server = SimpleXMLRPCServer(("localhost", 8000))
server.register_function(findai,"findai")
load()
server.serve_forever()
Client:
import xmlrpclib
proxy = xmlrpclib.ServerProxy("http://localhost:8000/")
candidate = proxy.findai(1)
print "the %d-th number of a is %d" %(1, candidate)
2. 數據端 + 網絡端
Client:
import xmlrpclib
proxy = xmlrpclib.ServerProxy("http://localhost:8000/")
candidate = proxy.findai(1)
print "the %d-th number of a is %d" %(1, candidate)
from bottle import route, run, template
@route('/hello/<name>')
def index(name):
return template('<b> hello {{name}} </b>', name=candidate)
run(host="localhost", port=8086)
注意事項：
1. 通信數據類型
注意通訊數據類型只能是python的built-in類型（而不能是numpy類型），所以其他類型應轉換為str類型（client端用ast.literal_eval從str轉回來）或者更方便的用list（直接server端tolist轉，client端numpy.array解）；
否則會報錯：
xmlrpclib.Fault: <Fault 8002: "Can't serialize output: cannot marshal <type 'numpy.float64'> objects">
以string為例（其實tolist更簡單），
Server:
from SimpleXMLRPCServer import SimpleXMLRPCServer
global a
import ast
from cStringIO import StringIO
from numpy.lib import format
import numpy
class T:
def to_string(self,arr):
f = StringIO()
if type(arr)==numpy.ndarray:
format.write_array(f,arr)
s = f.getvalue()
elif isinstance(arr,str)==False:
s = str(arr)
return s
def from_string(self,s):
if s[0]!="[": # converted from numpy array
f = StringIO(s)
arr = format.read_array(f)
else:
arr = ast.literal_eval(s)
return arr
def load(self):
global a
a = [1 ,2, 24]
return a
def ret_a(self):
global a
return a
server = SimpleXMLRPCServer(("localhost", 8002))
server.register_instance(T())
srv = T()
srv.load()
server.serve_forever()
Client:
import xmlrpclib
proxy = xmlrpclib.ServerProxy("http://localhost:8002/")
candidate = proxy.ret_a()
print "the variable 'a' in server is "+ str((proxy.from_string(candidate)))
2. 通訊字符編碼問題
注意通訊字符必須是unicode編碼，用中文的時候要小心。
所以中文的case下，在server段執行：
def gbk_to_unicode(s):
return s.decode('gbk').encode('utf-8').decode('latin1')
client端執行：
def unicode_to_gbk(s):
return s.encode('latin1').decode('utf-8').encode('gbk')
for example,
Server:
from SimpleXMLRPCServer import SimpleXMLRPCServer
global a
import ast
from cStringIO import StringIO
from numpy.lib import format
import numpy
import sys
def gbk_to_unicode(s):
return s.decode('gbk').encode('utf-8').decode('latin1')
class T:
def load(self): # load a dictionary with gbk elements
global a
a = {"1,1":["小","蘋果"],"1,2":[1,2]}
def printf(self,s): # receive unicode, return unicode
print "received string : "+ s #unicode
return s
def idx(self,s): # transfer gbk -> unicode to client
global a
return [gbk_to_unicode(x) for x in a.get(s,[])]
reload(sys)
sys.setdefaultencoding('gbk')
server = SimpleXMLRPCServer(("localhost", 8002))
server.register_instance(T())
srv = T()
srv.load()
server.serve_forever()
Client:
import xmlrpclib
proxy = xmlrpclib.ServerProxy("http://localhost:8002/")
# method 1. 用unicode編碼
s = u"美女"
print "the variable to transfer is "+ s
res_u1 = proxy.printf(s)
# method 2. decode to unicode
s = "美女"
print "the variable to transfer is "+ s
res_u2 = proxy.printf(s.decode('latin1'))
assert res_u1 == res_u2
res_gbk = res_u1.encode('latin1')
print res_gbk
# 再進一步
def unicode_to_gbk(s):
return s.encode('latin1').decode('utf-8').encode('gbk')
res = proxy.idx("1,1") # receive unicode
a = [unicode_to_gbk(s) for s in res] # transfer unicode->gbk
print a[0], a[1]
