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 countrypublic void initRates(){exchangerate.put("UK", new Float(0.72));exchangerate.put("Sweden", new Float(200));}//add a new ratepublic void addRates(String country,float rate){exchangerate.put(country, new Float(rate));}@Overridepublic float convert(float amount, String country) {Float xchrate = exchangerate.get(country);if (xchrate != null){return amount*(xchrate.floatValue());}elsereturn -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 leaseprotected 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.@Overridepublic 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.@Overridepublic 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CurrencyConvertServiceInterfaceCurrencyConvertServiceProxy 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 ListenerDiscoveryListener 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();}}@Overridepublic void run() {while(true){try {Thread.sleep(1000000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.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。