第七章 Join Manager

寻找一个lookup service包括一系列普通的步骤。他们随后的交互也包括了一些一般的步骤。所以
我们用一个join manager把这些步骤封装成一个有用的类。

1、 Join Manager

一个服务要使自己可用通常有以下策略：

（1） 发现可用的服务定位器（service locators）。
（2） 注册到找到的locator上（Register with all of them）
（3） 一直重新注册（Keep re-registering till the end of time）
（4） 如果状态改变了，通知给所有注册服务的locators。

package joinmgr;
// import net.jini.discovery.LookupDiscovery;
// import net.jini.discovery.DiscoveryListener;
// import net.jini.discovery.DiscoveryEvent;
// import net.jini.core.lookup.ServiceRegistrar;
// import net.jini.core.lookup.ServiceItem;
// import net.jini.core.lookup.ServiceRegistration;
// import net.jini.core.lease.Lease;
import com.sun.jini.lookup.JoinManager;
import net.jini.core.lookup.ServiceID;
import com.sun.jini.lookup.ServiceIDListener;
import com.sun.jini.lease.LeaseRenewalManager;
/**
 * FileClassifierServer.java *
    * Created: Wed Mar 17 14:23:44 1999 
    * @author Jan Newmarch 
    * @version
    */

public class FileClassifierServer implements ServiceIDListener {    
    public static void main(String argv[]) {
     	new FileClassifierServer();
    }

    public FileClassifierServer() {
     	/** WE JUNK ALL OF THIS CODE
	        LookupDiscovery discover = null;
        try {
            discover = new LookupDiscovery(LookupDiscovery.ALL_GROUPS);
        } catch(Exception e) {
            System.err.println(e.toString());
            System.exit(1);
        }
        discover.addDiscoveryListener(this);
        // stay around long enough to receive replies
        try {
            Thread.currentThread().sleep(10000L);
        } catch(java.lang.InterruptedException e) {
            // do nothing
        }	*/
	
/** AND REPLACE IT WITH THIS */	

    JoinManager joinMgr = null;
  	try {
	    joinMgr = new JoinManager(new FileClassifierImpl(), null, 
	              this,new LeaseRenewalManager());
 	} catch(Exception e) {
	      e.printStackTrace();
   	  System.exit(1);
 	}
        // stay around long enough to receive replies
   try {
       Thread.currentThread().sleep(1000000L);
   } catch(java.lang.InterruptedException e) {
            // do nothing
   }
}

public void serviceIDNotify(ServiceID serviceID) {
	    System.out.println("got service ID " + serviceID.toString());
}
    /*    
    public void discovered(DiscoveryEvent evt) {
        ServiceRegistrar[] registrars = evt.getRegistrars();
        for (int n = 0; n < registrars.length; n++) {
            ServiceRegistrar registrar = registrars[n];
	    ServiceItem item = new ServiceItem(null, new FileClassifierImpl(), null);

	    ServiceRegistration reg = null;	    try {
		reg = registrar.register(item, Lease.FOREVER);
	    } catch(java.rmi.RemoteException e) {
		System.err.println("Register exception: " + e.toString());
		}
	    System.out.println("service registered");	}    }
    public void discarded(DiscoveryEvent evt) {    } 
   */       

} // FileClassifierServer