Java RPC通信機制之XML-RPC.doc

Java RPC通信機制之XML-RPC二、舉例下面舉一個實際運用XML-RPC進行RPC調(diào)用的例子，XML-RPC規(guī)范有多種針對不同語言的實現(xiàn)，這里我們使用的是Apache的XML-RPC3.0RC1。在開始之前，需到/commons/index.html下載如下程序包：commons-codec-1.3（通用編碼/解碼算法實現(xiàn)，可參考/Java/Article/29795/1954?pf=true或/commons/codec/userguide.html來獲得該軟件包的詳細信息）commons-httpclient-3.0.1（HTTP協(xié)議的客戶端編程工具包，詳細介紹見/developerworks/cn/opensource/os-httpclient/）將上述通用工具包解壓后，拷貝其中的jar文件到XML-RPC解壓目錄的dist目錄中。并添加如下環(huán)境變量：XMLRPC_HOME XML-RPC的解壓目錄XMLRPC_LIB %XMLRPC_HOME%/distXMLRPCCLASSPATH %XMLRPC_LIB%/xmlrpc-common-3.0rc1.jar;%XMLRPC_LIB%/xmlrpc-server-3.0rc1.jar;%XMLRPC_LIB%/xmlrpc-client-3.0rc1.jar;%XMLRPC_LIB%/commons-httpclient-3.0.1.jar;%XMLRPC_LIB%/commons-codec-1.3.jar 整個應(yīng)用很簡單，通過XML-RPC調(diào)用Server端提供的HelloHandler.sayHello方法回顯一個字符串信息。下面是HelloHandler接口及其實現(xiàn)類相關(guān)代碼：/ HelloHandler.javapackage demo.xmlrpc; public interface HelloHandler public String sayHello(String str); / HelloHandlerImpl.javapackage demo.xmlrpc; public class HelloHandlerImpl implements HelloHandler public String sayHello(String str) return Hello, + str + !; 以下是對應(yīng)的Server端源代碼：/ Server1.javapackage demo.xmlrpc; import java.io.IOException;import java.io.OutputStream;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse; import org.apache.xmlrpc.XmlRpcException;import org.apache.xmlrpc.server.PropertyHandlerMapping;import org.apache.xmlrpc.server.XmlRpcServerConfigImpl;import org.apache.xmlrpc.webserver.XmlRpcServletServer; public class Server1 extends HttpServlet private XmlRpcServletServer server; public void init(ServletConfig pConfig) throws ServletException super.init(pConfig); try / create a new XmlRpcServletServer object server = new XmlRpcServletServer(); / set up handler mapping of XmlRpcServletServer object PropertyHandlerMapping phm = new PropertyHandlerMapping(); phm.addHandler(HelloHandler, HelloHandlerImpl.class); server.setHandlerMapping(phm); / more config of XmlRpcServletServer object XmlRpcServerConfigImpl serverConfig = (XmlRpcServerConfigImpl)server.getConfig(); serverConfig.setEnabledForExtensions(true); serverConfig.setContentLengthOptional(false); catch (XmlRpcException e) try log(Failed to create XmlRpcServer: + e.getMessage(), e); catch (Throwable ignore) throw new ServletException(e); public void doPost(HttpServletRequest pRequest, HttpServletResponse pResponse) throws IOException, ServletException server.execute(pRequest, pResponse); 以下是對應(yīng)的Client端源代碼：/ Client1.javapackage demo.xmlrpc; import java.io.IOException;import .MalformedURLException;import java.util.Vector;import .URL; import org.apache.xmlrpc.XmlRpcException;import org.apache.xmlrpc.client.XmlRpcClient;import org.apache.xmlrpc.client.XmlRpcClientConfigImpl; public class Client1 public static void main(String args) try / config client XmlRpcClientConfigImpl config = new XmlRpcClientConfigImpl(); config.setServerURL(new URL(http:/localhost:8080/jsp/XmlRpcServer); / should be modified according to your configuration of jsp container / create a new XmlRpcClient object and bind above config object with it XmlRpcClient client = new XmlRpcClient(); client.setConfig(config); / create parameter list Vector params = new Vector(); params.addElement(Tom); / execute XML-RPC call String result = (String) client.execute(HelloHandler.sayHello, params); System.out.println(result); catch (MalformedURLException e) System.out.println(e.toString(); catch (XmlRpcException e) System.out.println(e.toString(); catch (IOException e) e.printStackTrace(); 程序源碼中已包含了詳細的注釋，這里就不作過多解釋了。但需注意XmlRpcDemo_Client中的ServerURL信息應(yīng)根據(jù)自己的的jsp容器的配置作相應(yīng)調(diào)整，并需設(shè)置相應(yīng)的servlet-mapping信息，在我的jsp目錄（Tomcat5.5的Context之一）下的WEB_INF/web.xml文件中存在如下的servlet-mapping信息： XmlRpcServer demo.xmlrpc.Server1 XmlRpcServer /XmlRpcServer并且，上述Server1.class及其他相關(guān)類文件已被拷貝到j(luò)spWEB-INFclassesdemoxmlrpc目錄下。在啟動Tomcat并執(zhí)行java -classpath %CLASSPATH%;%XMLRPCCLASSPATH% demo.xmlrpc.Client1.java前，你應(yīng)該將%XMLRPC_HOME%/dist、%XMLRPC_HOME%/lib下的幾個jar文件（source就不用拷了）及前面下載的commons-codec-1.3.jar拷貝到%TOMCAT_HOME%/common/lib或jspWEB-INFlib下。Note：除了上面這種方式，你可以無需編寫任何Server端代碼，僅通過簡單配置完成上述功能，具體可參考：/xmlrpc/server.html接下來，作為比較，我們來看看XML-RPC2.0中應(yīng)該如何實現(xiàn)上述功能。以下是2.0版的Server程序：/ Server2.javapackage demo.xmlrpc; import java.io.IOException;import java.io.OutputStream; import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse; import org.apache.xmlrpc.XmlRpcServer; public class Server2 extends HttpServlet public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException XmlRpcServer xmlrpc = new XmlRpcServer(); xmlrpc.addHandler(HelloHandler, new HelloHandlerImpl(); byte result = xmlrpc.execute(request.getInputStream(); response.setContentType(text/xml); response.setContentLength(result.length); OutputStream out = response.getOutputStream(); out.write(result); out.flush(); 以下是2.0版的Client程序：/ Client2.javapackage demo.xmlrpc; import java.io.IOException;import .MalformedURLException;import java.util.Vector; import org.apache.xmlrpc.XmlRpcClient;import org.apache.xmlrpc.XmlRpcException; public class Client2 public static void main(String args) try XmlRpcClient xmlrpc = new XmlRpcClient(http:/localhost:8080/jsp/XmlRpcServer); Vector params = new Vector(); params.addElement(Tom); String result = (String) xmlrpc.execute(HelloHandler.sayHello, params); System.out.println(result); catch (MalformedURLException e) System.out.println(e.toString(); catch (XmlRpcException e) System.out.println(e.toString(); catch (IOException e) e.printStackTrace(); 總體上看，3.0比2.0在可配置性方面有了一些改進，其它方面則沒有太大變化，但由于功能模塊的分離，使得3.0較2.0顯得更為復(fù)雜，已經(jīng)習(xí)慣了2.0單一模塊風(fēng)格的開發(fā)者可能需要一些時間適應(yīng)這種變化。三、其它特性除了上面的基本功能，XML-RPC3還支持動態(tài)代理/工廠和異步通信等特性。通過運用動態(tài)代理特性，我們可以在Server端及Client端共享接口信息，從而在編譯期間進行必要的類型檢查，在XML-RPC內(nèi)部，所有的調(diào)用仍然是被動態(tài)轉(zhuǎn)發(fā)給XmlRpcClient對象來完成的。但要使用XML-RPC3的動態(tài)代理功能，相應(yīng)的服務(wù)器端的處理器類名稱必須是Client端接口類的全名（含包名，該名稱一般應(yīng)該與Server端接口類全名一致），否則將會導(dǎo)致調(diào)用失敗。以上面的HelloHandler接口為例，其對應(yīng)的處理器類名稱應(yīng)該為：demo.xmlrpc.HelloHandler。Note: 動態(tài)代理（JDK1.3引入）是Proxy模式、依賴注入（Dependency Injection）及動態(tài)代碼生成等技術(shù)相結(jié)合的一種應(yīng)用，在各新型Web應(yīng)用框架及容器中被廣泛采用。而要使用XML-RPC的異步通信功能，只需實現(xiàn)org.apache.xmlrpc.client.AsyncCallback接口，該接口包括兩個方法：public void handleResult(XmlRpcRequest pRequest, Object pResult);public void handleError(XmlRpcRequest pRequest, Throwable pError);此外，為了便于在普通應(yīng)用中使用XML-RPC，XML-RPC還提供了一個WebServer類，以便在應(yīng)用中內(nèi)嵌一個HTTP服務(wù)器，為Client程序提供HTTP服務(wù)。下面的范例演示了上面提到的幾種特性，以下是Server端代碼：/ Server3.javapackage demo.xmlrpc; 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 Server3 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(); phm.addHandler(demo.xmlrpc.HelloHandler, HelloHandlerImpl.class); xmlRpcServer.setHandlerMapping(phm); XmlRpcServerConfigImpl serverConfig = (XmlRpcServerConfigImpl)xmlRpcServer.getConfig(); serverConfig.setEnabledForExtensions(true); serverConfig.setContentLengthOptional(false); webServer.start(); 下面是Client端代碼：/ Client3.javapackage demo.xmlrpc; import .URL;import java.util.List;import java.util.Vector; import org.apache.xmlrpc.XmlRpcRequest;import org.apache.xmlrpc.XmlRpcException;import org.apache.xmlrpc.client.XmlRpcClient;import org.apache.xmlrpc.client.XmlRpcClientConfigImpl;import org.apache.xmlrpc.client.AsyncCallback;import org.apache.xmlrpc.client.util.ClientFactory; class EchoCallback implements AsyncCallback public void handleResult(XmlRpcRequest pRequest, Object pResult) System.out.println(Server returns: + (String)pResult); public void handleError(XmlRpcRequest pRequest, Throwable pError) System.out.println(Error occurs: + pError.getMessage(); public class Client3 public st