基于Java的CORBA技术复杂应用范例

基于Java的CORBA技术复杂应用范例

 

本文是继Hello World例程的又一个复杂应用范例，目的是看看真正的基于Java的CORBA技术应用是什么样子。

 

本文通过一个四则运算实例来展示一个基于Java的CORBA应用，范例如下：

 

一、定义IDL

 

module zzvcom{
            module cbrtest{
                 interface Calc{
                         void add(in long a,in long b,out long c);
                         void sub(in long a,in long b,out long c);
                         void muti(in long a,in long b,out long c);
                         void div(in long a,in long b,out long c);
                };
        };
};

 

二、根据IDL生成存根和代理等代码

 

idlj -fall Hello.idl

 

三、开发CORBA服务

 

import org.omg.CORBA.IntHolder;
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;
import zzvcom.cbrtest.Calc;
import zzvcom.cbrtest.CalcHelper;
import zzvcom.cbrtest.CalcPOA;

/**
* 四则运算的服务端实现
*
* @author leizhimin 2009-12-17 9:54:43
*/
class CalcImpl extends CalcPOA {
         private ORB orb;

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

         public void add( int a, int b, IntHolder c) {
                c.value = a + b;
        }

         public void sub( int a, int b, IntHolder c) {
                c.value = a - b;
        }

         public void muti( int a, int b, IntHolder c) {
                c = new IntHolder(a * b);
        }

         public void div( int a, int b, IntHolder c) {
                c = new IntHolder(a / b);
        }

         public void shutdown() {
                orb.shutdown( false);
        }
}

public class CalcServer {

         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();

                         //创建一个CalcImpl实例（servant），并注册到ORB上
                        CalcImpl calcImpl = new CalcImpl();
                        calcImpl.setORB(orb);

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

                         //得到一个根名称的上下文
                        org.omg.CORBA.Object objRef = orb.resolve_initial_references( "NameService");
                        NamingContextExt ncRef = NamingContextExtHelper.narrow(objRef);

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

                        System.out.println( "CalcServer 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( "CalcServer Exiting ...");
        }
}

 

四、开发客户端

 

import org.omg.CORBA.IntHolder;
import org.omg.CORBA.ORB;
import org.omg.CosNaming.NamingContextExt;
import org.omg.CosNaming.NamingContextExtHelper;
import zzvcom.cbrtest.Calc;
import zzvcom.cbrtest.CalcHelper;

/**
* 四则运算的客户端调用
*
* @author leizhimin 2009-12-17 10:35:32
*/
public class CalcClient {
         static Calc calcImpl;

         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");
                        NamingContextExt ncRef = NamingContextExtHelper.narrow(objRef);

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

                         //调用接口对象的方法
                        System.out.println( "Obtained a handle on server object: " + calcImpl);
                        System.out.println();
                        IntHolder add_val = new IntHolder();
                        calcImpl.add(1, 2, add_val);
                        System.out.println(add_val.value);
                } catch (Exception e) {
                        System.out.println( "ERROR : " + e);
                        e.printStackTrace(System.out);
                }
        }
}

 

五、启动CORBA服务器

 

先编译所有的Java文件：javac -Xlint:unchecked -d . *.java

 

编译后就可以调用了。

 

 

六、开启CORBA服务

 

 

七、启动CORBA客户端

 

 

可以看到当调用add（1，2）方法的时候，通过CORBA服务调用，从服务端获得了计算结果3.

 

这个例子与HelloWorld的例子不同在于：

 

1、如何组织接口的java包。

2、如何定义带参数，和返回值的方法。

3、如何调用带参数和返回值的方法。

 

理解了本例，就可以做更复杂的Java应用了。