发布一个JINI服务

这一篇文章讲解如何发布一个JINI的服务。

（参考的书是：JINI EXAMPLE BY EXAMPLE)

 

1.提供一个服务接口

首先，任何JINI服务都需要一个服务接口，表示这个服务能做什么。我们这里使用的是一个货币转换的服务，例如输入数量（单位为美元）和国家，表示将美元转换为某个国家的货币。

这个接口的代码如下：

package example.chapter2; public interface CurrencyConvertServiceInterface { public float convert(float amount,String country); }  

这里有几个注意，在eclipse中编辑时，需要导入的2个外部库为：jini2_1/lib/jini-core.jar;jini2_1/lib/jini-ext.jar;

 

2.创建一个服务的代理

服务接口只是发布出来给客户看的，里面没有任何实现，有实现的在JINI里称为服务代理。服务代理需要实现serializable接口。

服务代理类的代码如下：

package example.chapter2; import java.io.Serializable; import java.util.Hashtable; public class CurrencyConvertServiceProxy implements Serializable, CurrencyConvertServiceInterface { Hashtable<String,Float> exchangerate = new Hashtable<String,Float>(); public CurrencyConvertServiceProxy() { super(); } //initial the convert rate of country public void initRates(){ exchangerate.put("UK", new Float(0.72)); exchangerate.put("Sweden", new Float(200)); } //add a new rate public void addRates(String country,float rate){ exchangerate.put(country, new Float(rate)); } @Override public float convert(float amount, String country) { Float xchrate = exchangerate.get(country); if (xchrate != null){ return amount*(xchrate.floatValue()); }else return -1; } }  

这里初始化了2个国家的转化货币的比率。

 

3.发布服务

package example.chapter2; import java.io.IOException; import java.io.Serializable; import java.rmi.RMISecurityManager; import java.rmi.RemoteException; import java.util.HashMap; import java.util.Hashtable; import net.jini.core.discovery.LookupLocator; import net.jini.core.lookup.ServiceItem; import net.jini.core.lookup.ServiceRegistrar; import net.jini.core.lookup.ServiceRegistration; import net.jini.discovery.DiscoveryEvent; import net.jini.discovery.DiscoveryListener; import net.jini.discovery.LookupDiscoveryManager; //wrapper class that handles publishing the service item. public class CurrencyConvertService implements Runnable { //10 minute lease protected final int LEASE_TIME = 10*60*1000; protected HashMap registrations = new HashMap(); protected ServiceItem item; protected LookupDiscoveryManager discoverymanager; class Listener implements DiscoveryListener{ //called only when we explicitly discard a lookup service. @Override public void discarded(DiscoveryEvent ev) { ServiceRegistrar[] deadregs = ev.getRegistrars(); for (int i=0 ; i<deadregs.length ; i++){ registrations.remove(deadregs[i]); } } //called when we find a new lookup service. @Override public void discovered(DiscoveryEvent ev) { System.out.println("discovered a lookup service!......"); ServiceRegistrar[] newregs = ev.getRegistrars(); for (int i=0 ; i<newregs.length ; i++){ if(!registrations.containsKey(newregs[i])){ registerWithLookup(newregs[i]); } } } private synchronized void registerWithLookup(ServiceRegistrar registrar) { ServiceRegistration registration = null; try { registration = registrar.register(item, LEASE_TIME); } catch (RemoteException e) { System.out.println("Could not register!"); e.printStackTrace(); return; } //if this is our first registration ,use the service ID return to US. if(item.serviceID == null){ item.serviceID = registration.getServiceID(); System.out.println("set ServiceID to :" + item.serviceID); } registrations.put(registrar, registration); } } public CurrencyConvertService() throws IOException { //create an instance of the service proxy //第一步：为此服务创建一个代理对象，此对象实现CurrencyConvertServiceInterface CurrencyConvertServiceProxy proxyobj = createCurrencyProxy(); //create a service item to be added to the lookup service //第二步：将此代理对象放入一个能添加到lookup服务中的ServiceItem中 item = new ServiceItem(null, proxyobj, null); //set a security manager. //第三步：配置一个安全管理器 if(System.getSecurityManager() == null){ System.setSecurityManager(new RMISecurityManager()); } //create a discovery Listener DiscoveryListener myListener = new Listener(); //Search for the public group,which is named by the empty String. //第四步：查找一个lookup服务，使用空字符串来查找一个公共的共同体 LookupLocator look = new LookupLocator("jini://zz439"); discoverymanager = new LookupDiscoveryManager(new String[]{""}, new LookupLocator[]{look}, myListener); } private CurrencyConvertServiceProxy createCurrencyProxy() { CurrencyConvertServiceProxy proxyobj = new CurrencyConvertServiceProxy(); proxyobj.initRates(); return proxyobj; } /** * @param args */ public static void main(String[] args) { System.out.println("Started ....."); try { CurrencyConvertService hws = new CurrencyConvertService(); new Thread(hws).start(); } catch (IOException e) { System.out.println("cann't create service...."); e.printStackTrace(); } } @Override public void run() { while(true){ try { Thread.sleep(1000000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }  

发布服务需要首先发现一个查找服务。在JINI里用LookupDiscoveryManager类来进行寻找一个发现服务。

 

寻找到发现服务后，用一个Listener来进行工作。

 

当找到发现服务后，Listener调用discovery方法，在discovery方法里，进行服务的注册。

 

服务注册使用类初始化的时候建立的服务代理的对象。

 

4.测试

 

进入源码下的bin目录，执行代码如下：

C:/Documents and Settings/Administrator/workspace/JiniExample1/bin>java -cp D:/j

ini2_1/lib/jini-core.jar;D:/jini2_1/lib/jini-ext.jar;D:/jini2_1/lib/sun-util.jar

;.; -Djava.security.policy=C:/policy -Djava.rmi.server.codebase=http://zz439:808

1/ example.chapter2.CurrencyConvertService

Started .....

discovered a lookup service!......

set ServiceID to :2e68d56d-cebb-4d61-bcd8-bc99ce09a039

 

可以看到，服务已经被注册上了，而且在窗口界面上也可以看到一个新的服务。