package standardbeans; public class ServerImpl {     public final long startTime;     public ServerImpl() {         startTime = System.currentTimeMillis();     } } 

package standardbeans; public class ServerMonitor implements ServerMonitorMBean {     private final ServerImpl target;     public ServerMonitor(ServerImpl target){         this.target = target;     }     public long getUpTime(){         return System.currentTimeMillis() - target.startTime;     } } 

package standardbeans; import javax.management.MBeanServer; import javax.management.MBeanServerFactory; import javax.management.ObjectName; public class Main {     private static ObjectName objectName ;     private static MBeanServer mBeanServer;     public static void main(String[] args) throws Exception{         init();         manage();                    }     private static void init() throws Exception{         ServerImpl serverImpl = new ServerImpl();         ServerMonitor serverMonitor = new ServerMonitor(serverImpl);         mBeanServer = MBeanServerFactory.createMBeanServer();         objectName = new ObjectName("objectName:id=ServerMonitor1");         mBeanServer.registerMBean(serverMonitor,objectName);       }     private static void manage() throws Exception{         Long upTime = (Long) mBeanServer.getAttribute(objectName,         "upTime");         System.out.println(upTime);     }  } 

package dynamicbeans; import javax.management.*; import java.lang.reflect.*; public class ServerMonitor implements DynamicMBean {       private final ServerImpl target;         private MBeanInfo mBeanInfo;                  public ServerMonitor(ServerImpl target){         this.target = target;     }          //实现获取被管理的 ServerImpl 的 upTime     public long upTime(){         return System.currentTimeMillis() - target.startTime;     }  //javax.management.MBeanServer 会通过查询 getAttribute("Uptime") 获得 "Uptime" 属性值     public Object getAttribute(String attribute) throws AttributeNotFoundException,    MBeanException, ReflectionException {         if(attribute.equals("UpTime")){             return upTime();         }         return null;     }    //给出 ServerMonitor 的元信息。       public MBeanInfo getMBeanInfo() {         if (mBeanInfo == null) {             try {                 Class cls = this.getClass();                 //用反射获得 "upTime" 属性的读方法                 Method readMethod = cls.getMethod("upTime", new Class[0]);                  //用反射获得构造方法                 Constructor constructor = cls.getConstructor(new Class[]      {ServerImpl.class});                 //关于 "upTime" 属性的元信息:名称为 UpTime，只读属性(没有写方法)。                 MBeanAttributeInfo upTimeMBeanAttributeInfo = new MBeanAttributeInfo(                         "UpTime", "The time span since server start",                         readMethod, null);                 //关于构造函数的元信息                 MBeanConstructorInfo mBeanConstructorInfo = new MBeanConstructorInfo(                         "Constructor for ServerMonitor", constructor);                 //ServerMonitor 的元信息，为了简单起见，在这个例子里，                 //没有提供 invocation 以及 listener 方面的元信息                  mBeanInfo = new MBeanInfo(cls.getName(),                         "Monitor that controls the server",                         new MBeanAttributeInfo[] { upTimeMBeanAttributeInfo },                         new MBeanConstructorInfo[] { mBeanConstructorInfo },                         null, null);                             } catch (Exception e) {                 throw new Error(e);             }         }         return mBeanInfo;     }     public AttributeList getAttributes(String[] arg0) {                 return null;     }              public Object invoke(String arg0, Object[] arg1, String[] arg2)    throws MBeanException,    ReflectionException {                 return null;     }     public void setAttribute(Attribute arg0) throws AttributeNotFoundException,    InvalidAttributeValueException, MBeanException, ReflectionException {         return;             }     public AttributeList setAttributes(AttributeList arg0) {                 return null;     }    }