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 channelEventChannelImpl eventChannel = new EventChannelImpl(orb, rootPoa);ncExt.rebind(ncExt.to_name("NewsBC.EventChannel"),rootPoa.servant_to_reference(eventChannel));// Obtain the push consumer proxy objectPushSupplierImpl 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();}}}