Web Services：Apache XML-RPC

XML-RPC（http://ws.apache.org/xmlrpc/ ）的全称是XML Remote Procedure Call，即XML远 程方法 调 用。是JAVA 实现 的XML-RPC。

这种远程过程调用使用http作为传输协议，XML作为传送信息的编码格式。Xml-Rpc的定义尽可能的保持了简单，但同时能够传送、处理、返回复杂的数据结构。

XML-RPC是工作在Internet上的远程过程调用协议。一个XML-RPC消息就是一个请求体为xml的http-post请求，被调用的方法在服务器端执行并将执行结果以xml格式编码后返回。

■All primitive Java types are supported, including long, byte, short, and double.

■Calendar objects are supported. In particular, timezone settings, and milliseconds may be sent.

■DOM nodes, or JAXB objects, can be transmitted. So are objects implementing the java.io.Serializable interface.

■Both server and client can operate in a streaming mode, which preserves resources much better than the default mode, which is based on large internal byte arrays.

概念图如下：

和RMI类似，需要服务器类和客户端类。还需要配置web.xml.

服务器类代码片段：

package org.apache.xmlrpc.demo.webserver;

import java.net.InetAddress;

import org.apache.xmlrpc.common.TypeConverterFactoryImpl;

import org.apache.xmlrpc.demo.webserver.proxy.impls.AdderImpl;

import org.apache.xmlrpc.server.PropertyHandlerMapping;

import org.apache.xmlrpc.server.XmlRpcServer;

import org.apache.xmlrpc.server.XmlRpcServerConfigImpl;

import org.apache.xmlrpc.webserver.WebServer;

public class Server {

private static final int port = 8080;

public static void main(String[] args) throws Exception {

WebServer webServer = new WebServer(port);

XmlRpcServer xmlRpcServer = webServer.getXmlRpcServer();

PropertyHandlerMapping phm = new PropertyHandlerMapping();

/* Load handler definitions from a property file.

* The property file might look like:

*   Calculator=org.apache.xmlrpc.demo.Calculator

*   org.apache.xmlrpc.demo.proxy.Adder=org.apache.xmlrpc.demo.proxy.AdderImpl

*/

phm.load(Thread.currentThread().getContextClassLoader(),"MyHandlers.properties");

/* You may also provide the handler classes directly,

* like this:

* phm.addHandler("Calculator",

*     org.apache.xmlrpc.demo.Calculator.class);

* phm.addHandler(org.apache.xmlrpc.demo.proxy.Adder.class.getName(),

*     org.apache.xmlrpc.demo.proxy.AdderImpl.class);

*/

xmlRpcServer.setHandlerMapping(phm);

XmlRpcServerConfigImpl serverConfig =

(XmlRpcServerConfigImpl) xmlRpcServer.getConfig();

serverConfig.setEnabledForExtensions(true);

serverConfig.setContentLengthOptional(false);

webServer.start();

}

}

web.xml配置片段：

<servlet>

<servlet-name>XmlRpcServlet</servlet-name>

<servlet-class>org.apache.xmlrpc.webserver.XmlRpcServlet</servlet-class>

<init-param>

<param-name>enabledForExtensions</param-name>

<param-value>true</param-value>

<description>

Sets, whether the servlet supports vendor extensions for XML-RPC.

</description>

</init-param>

</servlet>

<servlet-mapping>

<servlet-name>XmlRpcServlet</servlet-name>

<url-pattern>/xmlrpc</url-pattern>

</servlet-mapping>

客户端代码片段：

package web.service.xml.rpc;

import java.net.MalformedURLException;

import java.net.URL;

import org.apache.xmlrpc.XmlRpcException;

import org.apache.xmlrpc.client.XmlRpcClient;

import org.apache.xmlrpc.client.XmlRpcClientConfigImpl;

import org.apache.xmlrpc.client.XmlRpcCommonsTransportFactory;

import org.apache.xmlrpc.client.util.ClientFactory;

public class Client {

public static void main(String[] args) throws Exception {

// create configuration

XmlRpcClientConfigImpl config = new XmlRpcClientConfigImpl();

config.setServerURL(new URL("http://127.0.0.1:8080/WEBXMLRPC"));

config.setEnabledForExtensions(true);

config.setConnectionTimeout(60 * 1000);

config.setReplyTimeout(60 * 1000);

XmlRpcClient client = new XmlRpcClient();

// use Commons HttpClient as transport

client.setTransportFactory(

new XmlRpcCommonsTransportFactory(client));

// set configuration

client.setConfig(config);

// make the a regular call

Object[] params = new Object[]

{ new Integer(2), new Integer(3) };

Integer result = (Integer) client.execute("calculator_test.add", params);

System.out.println("2 + 3 = " + result);

}

}

这里的calculator_test.add关键字是在MyHandlers.properties中配置的。add是方法名。

配置例子：calculator_test=web.service.xml.rpc.Calculator

Calculator类定义如下：

package web.service.xml.rpc;

public class Calculator {

public int add(int i1, int i2) {

return i1 + i2;

}

public int subtract(int i1, int i2) {

return i1 - i2;

}

}