CORBA版HelloWorld

CORBA，是一个很古老的技术，甚至诞生于Java之前，不过随着WebService、SOA、RMI等等技术的出现，CORBA由于过于复杂而渐渐淡出了人们的视线，不过在一些交互性很强的系统异构应用领域，CORBA似乎很重要，比如中国联通、移动、美国的数字电视系统应用领域，是CORBA把整个系统核心部分集成起来的。如果没有异构的、需要预留标准接口的、交互性很强的应用，你不应该考虑使用COBRA。

 

CORBA目前的最近版本规范是3.2，Java1.5、1.6均支持该版本。

 

CORBA比较亲和C++，对Java程序员来说，开始CORBA应用难度比较大，以至于网上找一个真正能跑的HelloWorld都很难。

 

下面是我经过阅读SUN的CORBA文档，所做的一个完整的HelloWorld实例：

 

一、定义IDL

 

module HelloApp{ 
        interface Hello{ 
                string sayHello(); 
                oneway void shutdown(); 
        }; 
};

 

没有IDL的专门的开发工具，写起来容易出错，而且不美观，IDEA勉强支持语法高亮，但不支持格式化和语法校验！

 

二、从IDL生成存根

 

进入IDL文件存放目录，然后执行：idlj -fall Hello.idl

 

会生成一批Java文件：

 

helloCorba\src\HelloApp

HelloPOA.java 
_HelloStub.java 
HelloHolder.java 
HelloHelper.java 
Hello.java 
HelloOperations.java

 

三、实现IDL接口，开发服务端程序

 

import HelloApp.Hello; 
import HelloApp.HelloHelper; 
import HelloApp.HelloPOA; 
import org.omg.CORBA.ORB; 
import org.omg.CosNaming.NameComponent; 
import org.omg.CosNaming.NamingContextExt; 
import org.omg.CosNaming.NamingContextExtHelper; 
import org.omg.PortableServer.POA; 
import org.omg.PortableServer.POAHelper; 

class HelloImpl extends HelloPOA { 
        private ORB orb; 

        public void setORB(ORB orb_val) { 
                orb = orb_val; 
        } 

        // implement sayHello() method 
        public String sayHello() { 
                return "\nHello world !!\n"; 
        } 

        // implement shutdown() method 
        public void shutdown() { 
                orb.shutdown(false); 
        } 
} 

public class HelloServer { 

        public static void main(String args[]) { 
                try { 
                        //创建一个ORB实例 
                        ORB orb = ORB.init(args, null); 

                        //得到一个RootPOA的引用，并激活POAManager 
                        POA rootpoa = POAHelper.narrow(orb.resolve_initial_references("RootPOA")); 
                        rootpoa.the_POAManager().activate(); 

                        // create servant and register it with the ORB 
                        //创建一个HelloImpl实例（servant），并注册到ORB上 
                        HelloImpl helloImpl = new HelloImpl(); 
                        helloImpl.setORB(orb); 

                        //从服务中得到对象的引用 
                        org.omg.CORBA.Object ref = rootpoa.servant_to_reference(helloImpl); 
                        Hello href = HelloHelper.narrow(ref); 

                        //得到一个根名称的上下文 
                        org.omg.CORBA.Object objRef = orb.resolve_initial_references("NameService"); 
                        // Use NamingContextExt which is part of the Interoperable 
                        // Naming Service (INS) specification. 
                        NamingContextExt ncRef = NamingContextExtHelper.narrow(objRef); 

                        //在命名上下文中绑定这个对象 
                        String name = "Hello"; 
                        NameComponent path[] = ncRef.to_name(name); 
                        ncRef.rebind(path, href); 

                        System.out.println("HelloServer ready and waiting ..."); 

                        //启动线程服务，等待客户端的调用 
                        orb.run(); 
                }catch (Exception e) { 
                        System.err.println("ERROR: " + e); 
                        e.printStackTrace(System.out); 
                } 
                System.out.println("HelloServer Exiting ..."); 
        } 
}

 

四、实现CORBA的客户端

 

import HelloApp.Hello; 
import HelloApp.HelloHelper; 
import org.omg.CORBA.ORB; 
import org.omg.CosNaming.NamingContextExt; 
import org.omg.CosNaming.NamingContextExtHelper; 

public class HelloClient { 
        static Hello helloImpl; 

        public static void main(String args[]) { 
                try { 
                        //创建一个ORB实例 
                        ORB orb = ORB.init(args, null); 

                        //获取根名称上下文 
                        org.omg.CORBA.Object objRef = orb.resolve_initial_references("NameService"); 
                        // Use NamingContextExt instead of NamingContext. This is 
                        // part of the Interoperable naming Service. 
                        NamingContextExt ncRef = NamingContextExtHelper.narrow(objRef); 

                        //从命名上下文中获取接口实现对象 
                        String name = "Hello"; 
                        helloImpl = HelloHelper.narrow(ncRef.resolve_str(name)); 

                        //调用接口对象的方法 
                        System.out.println("Obtained a handle on server object: " + helloImpl); 
                        System.out.println(helloImpl.sayHello()); 
                        helloImpl.shutdown(); 

                } catch (Exception e) { 
                        System.out.println("ERROR : " + e); 
                        e.printStackTrace(System.out); 
                } 
        }

}

 

五、运行

 

1）运行CORBA服务

orbd -ORBInitialPort 1050 -ORBInitialHost 192.168.14.117

 

2）运行CORBA应用的服务端

java HelloServer -ORBInitialPort 1050

 

输出：

HelloServer ready and waiting ... 
HelloServer Exiting ...

 

3）运行CORBA应用的客户端

java HelloClient -ORBInitialHost 192.168.14.117 -ORBInitialPort 1050

 

Obtained a handle on server object: IOR:000000000000001749444c3a48656c6c6f4170702f48656c6c6f3a312e30000000000001000000000000008a000102000000000f3139322e3136382e31342e313137000006db000000000031afabcb00000000206d3bb80000000001000000000000000100000008526f6f74504f410000000008000000010000000014000000000000020000000100000020000000000001000100000002050100010001002000010109000000010001010000000026000000020002 

Hello world !!

 

呵呵，很垃圾吧，但是客户要，我们就做！

 

太费劲了，如果做一个接口很复杂，参数很多，自定义类型不少的CORBA应用，复杂度将很好，如果经常改，那就更加郁闷了。