使用Java进行CORBA编程-JacORB-Event Service

CORBA的Event Service提供了一种分发事件通知的方式。
Event Servcie的Event Channel从一个Supplier那里得到事件，发送到一个或多个Consumer那里。
事件可以用push的方式发送，也可以用pull的方式发送，也可以混合push和pull。

Event Service的实现可以看JacORB安装目录下的\idl\omg目录中的IDL文件。
CosEventComm.idl
CosEventChannelAdmin.idl
用类图来表示：

通过这个类图，可以很清晰的得到使用Event Service的步骤。以push mode为例，
Server侧（Supplier）
1）创建一个类，继承自PushSupplierPOA，这个类就是Server侧的Supplier的实现类。
2）创建一个org.jacorb.events.EventChannelImpl的对象，它实现了EventChannel的接口。
然后向NameService注册这个Channel，注册时提供一个Channel名。
3）调用EventChannelImpl对象的for_suppliers()方法，得到一个SupplierAdmin对象。
4）调用SupplierAdmin对象的obtain_push_consumer()方法，得到一个ProxyPushConsumer对象。
5）创建1）中的Supplier的实现类的一个实例。
在上面4）得到的ProxyPushConsumer对象上调用connect_push_supplier()方法，
把Supplier的实现类的实例传给此方法。
6）现在Server侧已经连接到Event Channel，可以调用ProxyPushConsumer对象的push()方法来发送事件通知给Channel了。

Client侧（Consumer）
1）创建一个类，继承自PushConsumerPOA，这个类就是Client侧的Consumer的实现类。
这个类的push()方法，在Event Channel发送事件通知过来的时候会被调用。
在这里添加对事件通知的处理代码。
2）向NameService查询并获得Event Channel的引用(EventChannel对象)，查询时需要提供Server侧注册时使用的Channel名。
3）调用EventChannel对象的for_consumers()方法，得到一个ConsumerAdmin对象。
4）调用ConsumerAdmin对象的obtain_push_supplier()方法，得到一个ProxyPushSupplier对象。
5）创建1）中的Consumer的实现类的一个实例。
在上面4）得到的ProxyPushSupplier对象上调用connect_push_consumer()方法，
把Consumer的实现类的实例传给此方法。
6）现在Client侧也已经连接到Event Channel。
这时候如果Server侧（Supplier）发送事件通知，Consumer的实现类的push()方法就会被调用了。

下面提供一个例程，运行此例子需要启动NameService，
启动方法和例程的启动方法见http://blog.csdn.net/fw0124/article/details/7188844

Server代码
1）PushSupplierImpl

package learning.corba.event.newsbroadcast.server;

import org.omg.CosEventComm.PushSupplierPOA;

public class PushSupplierImpl extends PushSupplierPOA {

	public void disconnect_push_supplier() {
		System.out.println("disconnect_push_supplier");
	}

}

2）NewsBCServer

package learning.corba.event.newsbroadcast.server;

import java.util.Properties;

import org.jacorb.events.EventChannelImpl;
import org.omg.CORBA.Any;
import org.omg.CORBA.ORB;
import org.omg.CosEventChannelAdmin.ProxyPushConsumer;
import org.omg.CosEventChannelAdmin.SupplierAdmin;
import org.omg.CosEventComm.Disconnected;
import org.omg.CosEventComm.PushSupplierHelper;
import org.omg.CosNaming.NamingContextExt;
import org.omg.CosNaming.NamingContextExtHelper;
import org.omg.PortableServer.POA;
import org.omg.PortableServer.POAHelper;

public class NewsBCServer implements Runnable {

	private ORB orb;
	private ProxyPushConsumer proxyPushConsumer;

	public static void main(String[] args) {
		try {
			Properties props = new Properties();
			props.put("org.omg.PortableInterceptor.ORBInitializerClass.bidir_init",
					  "org.jacorb.orb.giop.BiDirConnectionInitializer");
			
			ORB orb = ORB.init(args, props);
			POA rootPoa = POAHelper.narrow(
					orb.resolve_initial_references("RootPOA"));
			rootPoa.the_POAManager().activate();
				
			NamingContextExt ncExt = NamingContextExtHelper.narrow(
					orb.resolve_initial_references("NameService"));
			
			// Create event channel
			EventChannelImpl eventChannel = new EventChannelImpl(orb, rootPoa);
			ncExt.rebind(ncExt.to_name("NewsBC.EventChannel"),
					rootPoa.servant_to_reference(eventChannel));
			
			// Obtain the push consumer proxy object
			PushSupplierImpl pushSupplierImpl = new PushSupplierImpl();
			SupplierAdmin supplierAdmin = eventChannel.for_suppliers();
			ProxyPushConsumer proxyPushConsumer = supplierAdmin.obtain_push_consumer();
			proxyPushConsumer.connect_push_supplier(
					PushSupplierHelper.narrow(rootPoa.servant_to_reference(pushSupplierImpl)));
			
			Thread t = new Thread(new NewsBCServer(orb, proxyPushConsumer));
			t.start();
			
			orb.run();
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	public NewsBCServer(ORB orb, ProxyPushConsumer proxyPushConsumer) {
		this.orb = orb;
		this.proxyPushConsumer = proxyPushConsumer;
	}

	public void run() {
		int i = 0;
		
		try {
			while(!Thread.interrupted()) {
				Any event = this.orb.create_any();
				event.insert_long(i++);
				
				this.proxyPushConsumer.push(event);
				Thread.sleep(3000);
			}
		} catch (InterruptedException e) {
			e.printStackTrace();
		} catch (Disconnected e) {
			e.printStackTrace();
		}
		
		this.proxyPushConsumer.disconnect_push_consumer();
		this.orb.shutdown(true);
	}
}

Client代码
1）PushConsumerImpl

package learning.corba.event.newsbroadcast.client;

import org.omg.CORBA.Any;
import org.omg.CORBA.ORB;
import org.omg.CosEventChannelAdmin.ProxyPushConsumer;
import org.omg.CosEventChannelAdmin.ProxyPushSupplier;
import org.omg.CosEventComm.Disconnected;
import org.omg.CosEventComm.PushConsumerPOA;

public class PushConsumerImpl extends PushConsumerPOA {
	
	private ORB orb;
	private ProxyPushSupplier proxyPushSupplier;
	private int eventCount = 0;
	
	public PushConsumerImpl(ORB orb, ProxyPushSupplier proxyPushSupplier) {
		this.orb = orb;
		this.proxyPushSupplier = proxyPushSupplier;
	}
	
	public void disconnect_push_consumer() {
		System.out.println("disconnect_push_consumer");
	}

	public void push(Any event) throws Disconnected {
		System.out.println("event:" + event.extract_long());
		if (eventCount++ > 10) {
			proxyPushSupplier.disconnect_push_supplier();
			orb.shutdown(false);
		}		
	}
}

2）NewsBCClient

package learning.corba.event.newsbroadcast.client;

import java.util.Properties;

import org.omg.CORBA.ORB;
import org.omg.CosEventChannelAdmin.ConsumerAdmin;
import org.omg.CosEventChannelAdmin.EventChannel;
import org.omg.CosEventChannelAdmin.EventChannelHelper;
import org.omg.CosEventChannelAdmin.ProxyPushSupplier;
import org.omg.CosEventComm.PushConsumer;
import org.omg.CosEventComm.PushConsumerHelper;
import org.omg.CosNaming.NamingContextExt;
import org.omg.CosNaming.NamingContextExtHelper;
import org.omg.PortableServer.POA;
import org.omg.PortableServer.POAHelper;

public class NewsBCClient {
	public static void main(String[] args) {
		try {
			Properties props = new Properties();
			props.put("org.omg.PortableInterceptor.ORBInitializerClass.bidir_init",
			  	 	  "org.jacorb.orb.giop.BiDirConnectionInitializer");
			ORB orb = ORB.init(args, props);
			
			NamingContextExt ncExt = NamingContextExtHelper.narrow(
					orb.resolve_initial_references("NameService"));
			
			EventChannel eventChannel = EventChannelHelper.narrow(
					ncExt.resolve_str("NewsBC.EventChannel"));
			
			
			ConsumerAdmin consumerAdmin = eventChannel.for_consumers();
			ProxyPushSupplier proxyPushSupplier = consumerAdmin.obtain_push_supplier();

			POA rootPoa = POAHelper.narrow(orb
					.resolve_initial_references("RootPOA"));
			rootPoa.the_POAManager().activate();
			PushConsumerImpl pushConsumerImpl = new PushConsumerImpl(orb, proxyPushSupplier);
			PushConsumer pushConsumer = PushConsumerHelper.narrow(
					rootPoa.servant_to_reference(pushConsumerImpl));
			proxyPushSupplier.connect_push_consumer(pushConsumer);
			
			orb.run();			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}