Pyro4,全名Python Remote Object。
学习这个库主要是因为工作需要在Java中调用Python。Pyro库的主要作用是让我们的应用可以在network下相互通信,是个轻量级的库。对于返回值的类型支持强大。并且Pyro是100%用Python写的,兼容任何版本的Python,包括3.x。
Pyro4发布超过15年了,而且现在还在持续更新。
关于Pyro4的特点,上文中的在线文档首页列了27条,就不一一列举了。生产环境有用到,并且没有出现过任何问题。
前提,需要先Install Pyro4 module: 可以通过pip工具进行下载安装。
Mac OS系统自带Python2.7,不过我自己又装了Python3.6,于是对应的pip命令也默认变pip3,具体如下:
>pip3 -V >pip 9.0.1 from /Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages (python 3.6) >pip3 install Pyro4
Log表明已经装好: Successfully installed Pyro4-4.56 serpent-1.19
示例1: python server <---- python client
例子在Pyro4的官网首页上就有,我这里只是拷贝测试下:
Server端代码: # saved as greeting-server.py
import Pyro4 @Pyro4.expose class GreetingMaker(object): def get_fortune(self, name): return "Hello, {0}. Here is your fortune message:\n" \ "Behold the warranty -- the bold print giveth and the fine print taketh away.".format(name) daemon = Pyro4.Daemon() # make a Pyro daemon uri = daemon.register(GreetingMaker) # register the greeting maker as a Pyro object print("Ready. Object uri =", uri) # print the uri so we can use it in the client later daemon.requestLoop() # start the event loop of the server to wait for calls
运行后,输出: Ready. Object uri = PYRO:obj_73fa03c1a27b482195612fcd66357b3a@localhost:58672
客户端: # saved as greeting-client.py
import Pyro4 uri = input("What is the Pyro uri of the greeting object? ").strip() name = input("What is your name? ").strip() greeting_maker = Pyro4.Proxy(uri) # get a Pyro proxy to the greeting object print(greeting_maker.get_fortune(name)) # call method normally
运行后(若报错Connection refused,请看下文的问题1):
What is the Pyro uri of the greeting object? PYRO:obj_73fa03c1a27b482195612fcd66357b3a@localhost:58672
What is your name? allen
Hello, allen. Here is your fortune message:
Behold the warranty -- the bold print giveth and the fine print taketh away.
示例2: python server <---- java client
这里用到一个第三方库叫 pyrolite-4.10.jar(最新版本是2017-02,v4.18),具体在线资源如下:
Github(大量例子及源码): https://github.com/irmen/Pyrolite
在线Python文档: http://pythonhosted.org/Pyro4/pyrolite.html
Maven仓库: https://mvnrepository.com/artifact/net.razorvine/pyrolite/4.10
用Maven的话会自动下载依赖,如需要自己添加,需加依赖: serpent-1.12.jar
具体例子,github上有,我拷贝下:
先是服务端(Python):
注:
1. 比第一个例子中的稍微复杂,是因为使用了name-server(可自定义,比url好记、方便)。
2. 注解@Pyro4.expose表示要暴露的范围,若加在class前面说明里面所有的方法都可以被客户端所调用,若加在单个方法中,那么其它方法对外则不可见。
3. 加了security: hmac,这段代码只是起到安全作用,可不写,具体参见: http://pythonhosted.org/Pyro4/security.html
4. 设了最简单的String参数,当然其它类型的也都可以支持。
import Pyro4 class GreetingMakerJava(object): @Pyro4.expose def get_fortune(self, name): return "Hello, " + name; daemon = Pyro4.core.Daemon() # make a Pyro daemond daemon._pyroHmacKey = b'demokey' ns = Pyro4.locateNS() # find the name server uri = daemon.register(GreetingMakerJava) # register the greeting maker as a Pyro object ns.register("example.greeting", uri) # register the object with a name in the name server print("Ready.") print(list(ns.list(prefix="example.").keys())) daemon.requestLoop() # start the event loop of the server to wait for calls
Java客户端:
import net.razorvine.pyro.Config; import net.razorvine.pyro.NameServerProxy; import net.razorvine.pyro.PyroProxy; public class TestPython { public static void main(String[] args) throws Exception { Config.METADATA = false; // Pyro4.56 have some bugs to get metadata. NameServerProxy ns = NameServerProxy.locateNS(null); PyroProxy remoteobject = new PyroProxy(ns.lookup("example.greeting")); remoteobject.pyroHmacKey = "demokey".getBytes(); Object result = remoteobject.call("get_fortune", "allen"); String message = (String)result; System.out.println("result message=" + message); remoteobject.close(); ns.close(); } } // result message=Hello, allen
-------------------------------------------------------------------------
使用过程中遇到的问题:
1. 在运行第1个例子的客户端,遇到错误: ConnectionRefusedError: [Errno 61] Connection refused
需要打开python的name service:
>python3 -m Pyro4.naming Not starting broadcast server for localhost. NS running on localhost:9090 (127.0.0.1) Warning: HMAC key not set. Anyone can connect to this server! URI = PYRO:Pyro.NameServer@localhost:9090
参考: http://stackoverflow.com/questions/34499331/pyro4-failed-to-locate-the-nameserver
2. 在运行第2个例子的客户端,遇到错误: Exception in thread "main" java.lang.ClassCastException: java.util.ArrayList cannot be cast to java.util.HashSet
尝试解决,加上Config.METADATA = false;