QUALITY OF SERVICE AND AOP in Font

Printer DataMatrix in Font QUALITY OF SERVICE AND AOP

Listing 9-21. A Simple Client Program for the Stats MBean package aop.management.jmx.simple; public class JMXExample { private static Stats statistics = new Stats(); public static void sendOrder(float amount) { if (amount>0) { statistics.incOrders(); statistics.addAmount(amount); } else { statistics.setStatus("KO"); try { Thread.sleep(200); } catch (InterruptedException e) { } statistics.setStatus("OK"); } }

public static void main(String[] str) throws Exception { Injector injection = new Injector(); injection.start(); } } The sendOrder method is used by the Injector instance to simulate orders. If the passed amount is positive, statistics are updated. Otherwise, an error is generated, and the status attribute is set to KO for 200 milliseconds before being reset to OK . The Injector class shown in Listing 9-22 is a Java thread that generates arbitrary orders. More precisely, it generates ten random orders. Every five orders, an invalid order (with an amount of 1000) is generated. Listing 9-22. A Thread for the Random Generation of Orders package aop.management.jmx.simple; public class Injector extends Thread { public void run() { float amount = 0; for (int i=1;i<=10;i++) { try {

System.err.println("Order #"+i); sleep(Math.round(Math.random() * 5000)); } catch (InterruptedException e) {} if ((i%5)==0) { JMXExample.sendCommand(-1000); } else { amount = Math.round(Math.random() * 1500); JMXExample.sendCommand(amount); } } } }

To become a manageable resource, the Stats class must implement a StatsMBean interface, as shown in Listing 9-23. Listing 9-23. The MBean Interface for Ordering Statistics package aop.management.jmx.simple; public interface StatsMBean { public int getOrders(); public float getTotalAmount(); public String getStatus(); public void reset(); } With MX4J, you must also define a class named StatsMBeanDescription, which is used for documenting the attributes and methods of the MBean. This class is shown in Listing 9-24. Listing 9-24. The MX4J Stats Bean Description package aop.management.jmx.simple; import java.lang.reflect.Method; import mx4j.MBeanDescriptionAdapter; public class StatsMBeanDescription extends MBeanDescriptionAdapter { public String getAttributeDescription(String attribute) { if (attribute.equals("Orders")) { return "Number of orders "; } else if (attribute.equals("Status")) { return "Status of the ordering process"; } else if (attribute.equals("TotalAmount")) { return "Total amount of the orders";

} else { return "Unknown attribute"; } } public String getOperationDescription(Method method) { if (method.getName().equals("reset")) { return "Resets the attributes to their initial values "; } else { return "Unkown operation"; } } } Once we have defined our interface and description class, we can use the introduction mechanism of AOP to transform our Java class into a manageable resource. With JBoss AOP, an empty interceptor must be defined, as shown in Listing 9-25. Listing 9-25. An Empty Interceptor for Allowing Introductions package aop.management.jmx.simple; import org.jboss.aop.Interceptor; import org.jboss.aop.Invocation; import org.jboss.aop.InvocationResponse; public class StatsMBeanInterceptor implements Interceptor { public String getName() { return "StatsMBeanInterceptor"; } public InvocationResponse invoke(Invocation invocation) throws Throwable { return invocation.invokeNext(); } } Finally, jboss-aop.xml defines the introduction, as shown in Listing 9-26. Listing 9-26. The Deployment of the MBean-Interface Introduction <interceptor-pointcut methodFilter="NONE" constructorFilter="ALL" fieldFilter="NONE" class="aop.management.jmx.simple.Stats"> <interceptors> <interceptor class="aop.management.jmx.simple.StatsMBeanInterceptor"/> </interceptors> </interceptor-pointcut> <introduction-pointcut class="aop.management.jmx.simple.Stats">

<interfaces>aop.management.jmx.simple.StatsMBean</interfaces> </introduction-pointcut> In addition, the main class must be modified as shown in Listing 9-27. Listing 9-27. The Modification of the Example to Make it a JMX Client 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 package aop.management.jmx.simple; import import import import import import import import import import import import import import import import javax.management.MBeanServer; javax.management.MBeanServerFactory; javax.management.ObjectName; javax.management.JMException; javax.management.Attribute; javax.management.monitor.GaugeMonitor; javax.management.monitor.StringMonitor; javax.management.monitor.CounterMonitor; javax.management.NotificationListener; javax.management.Notification; java.net.URL; java.net.MalformedURLException; java.util.Map; java.util.HashMap; java.util.List; java.util.ArrayList;

public class JMXExample { private int port = 8080; private String host = "localhost"; private static Stats statistics = new Stats(); public static void sendCommand(float amount) { ... } public void start() throws JMException, MalformedURLException { MBeanServer server = MbeanServerFactory.createMBeanServer("OrderProcess"); ObjectName serverName = new ObjectName("Http:name=HttpAdaptor"); server.createMBean("mx4j.adaptor.http.HttpAdaptor",serverName,null); server.setAttribute(serverName,new Attribute("Port",new Integer(port))); server.setAttribute(serverName,new Attribute("Host",host)); ObjectName processorName = new ObjectName("Http:name=XSLTProcessor"); server.createMBean("mx4j.adaptor.http.XSLTProcessor",processorName,null); server.setAttribute(processorName, new Attribute("UseCache",new Boolean(false))); server.setAttribute(serverName, new Attribute("ProcessorName",processorName));