Java Corba

1）首先要熟悉idl语言，这个是专门进行接口设计的语言，它与java没关系，有自己的语法，具体的规则需要大家自己再网上研究，这里不多说了（或者访问如下网站详细察看http://www.iona.com/support/docs/manuals/orbix/33/html/orbix33cxx_pguide/IDL.html）。

module HelloApp
{

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

这里定义了一个简单的interface, 将其保存为hello.idl, 然后再dos命令框里面输入 idlj.exe -fall hello.idl 编译。之后会出现一个叫做HelloApp的目录，corba就是通过这个目录里面的类来进行c-s之间的数据沟通。

2）下一步，就是我们的server端：

// A server for the Hello object

import HelloApp.*;
import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
import org.omg.CORBA.*;
import org.omg.PortableServer.*;
import org.omg.PortableServer.POA;
import java.util.Properties;

public class HelloServer {

public static void main(String args[]) {
    try{
      // create and initialize the ORB
      ORB orb = ORB.init(args, null);

      // get reference to rootpoa & activate the POAManager
      POA rootpoa =
        (POA)orb.resolve_initial_references("RootPOA");
      rootpoa.the_POAManager().activate();

      // create servant and register it with the ORB
      HelloImpl helloImpl = new HelloImpl();
      helloImpl.setORB(orb);

      // get object reference from the servant
      org.omg.CORBA.Object ref =
        rootpoa.servant_to_reference(helloImpl);

      // and cast the reference to a CORBA reference
      Hello href = HelloHelper.narrow(ref);

      // get the root naming context
      // NameService invokes the transient name service
      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);

      // bind the Object Reference in Naming
      String name = "Hello1";
      NameComponent path[] = ncRef.to_name( name );
      ncRef.rebind(path, href);

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

      // wait for invocations from clients
      orb.run();
    }

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

      System.out.println("HelloServer Exiting ...");

} //end main
} // end class

将其保存为HelloServer.java.放在刚才的hello.idl的目录。编译这个文件就不多说了。

3）还记得在hello中定义的interface吗？我们需要对自己定义的接口中的方法进行实现，因此HelloImp.java

// The servant -- object implementation -- for the Hello
// example. Note that this is a subclass of HelloPOA, whose
// source file is generated from the compilation of
// Hello.idl using j2idl.

import HelloApp.*;
import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
import org.omg.CORBA.*;
import org.omg.PortableServer.*;
import org.omg.PortableServer.POA;

import java.util.Properties;

class HelloImpl extends HelloPOA //必须继承这个类，在helloApp目录中已自动生成

{
private ORB orb;

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

// implement sayHello() method
    public String sayHello()
    {
return " Hello world !! ";
    }

// implement shutdown() method
public void shutdown() {
    orb.shutdown(false);
}
} //end class
同样放在server所在目录中。

4）接下来是客户端（HelloClient.java）：

// A sample Java IDL object client application.
import HelloApp.*;
import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
import org.omg.CORBA.*;

public class HelloClient
{
static Hello helloImpl;
String [] x=new String[6];
public static void main(String args[]){
     try{
        // create and initialize the ORB
      ORB orb = ORB.init(args, null);

System.out.println("ORB initialised ");

        // get the root naming context
        org.omg.CORBA.Object objRef =
      orb.resolve_initial_references("NameService");

        // Use NamingContextExt instead of NamingContext,
        // part of the Interoperable naming Service.
        NamingContextExt ncRef =
          NamingContextExtHelper.narrow(objRef);

        // resolve the Object Reference in Naming
        String name = "Hello1";
        helloImpl =
          HelloHelper.narrow(ncRef.resolve_str(name));

        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);
   }
} //end main

} // end class

这个文件最好放在一个新建的目录，已表示和server有区别，放在一起也没有关系。如果分开的话，记着把HelloApp这个目录复制到client的目录来。

5）好啦！已经可以开始爽了，我们编译所有的java文件

6）再dos窗口输入orbd.exe –ORBInitialPort 1234（端口号可以自定义，但是记得s-c要保持一致）,启动corba服务。

7）启动服务器：java HelloServer –ORBInitialPort 1234 –ORBInitialHost localhost

8）启动客户端：java HelloClient –ORBInitialPort 1234 –ORBInitialHost localhost

9）严格执行上述过程是应该直接成功的。已经经过测试。

10）然后再仔细研究这段代码，你就会发现corba的奥秘了。
From: http://www.javaeye.com/topic/136691