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/xmlrpc")); 
        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; 
    } 
}