# CircuitBreakerJMX.java

    /*
     * Copyright 2009-2010 Rickard Öberg AB
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *     http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    package org.qi4j.library.circuitbreaker.jmx;

    import java.beans.PropertyChangeEvent;
    import java.beans.PropertyChangeListener;
    import java.beans.PropertyVetoException;
    import java.text.DateFormat;
    import java.util.Date;
    import javax.management.MBeanNotificationInfo;
    import javax.management.Notification;
    import javax.management.NotificationBroadcasterSupport;
    import javax.management.ObjectName;
    import org.qi4j.library.circuitbreaker.CircuitBreaker;

    /**
     * MBean for circuit breakers. Exposes CB properties and also the property changes as notifications.
     */
    public class CircuitBreakerJMX
            extends NotificationBroadcasterSupport
            implements org.qi4j.library.circuitbreaker.jmx.CircuitBreakerJMXMBean
    {
       CircuitBreaker circuitBreaker;

       public CircuitBreakerJMX(CircuitBreaker circuitBreaker, final ObjectName mbeanObjectName)
       {
          super(new MBeanNotificationInfo(new String[]{"serviceLevel", "status"}, Notification.class.getName(), "Circuit breaker notifications"));

          this.circuitBreaker = circuitBreaker;
          circuitBreaker.addPropertyChangeListener(new PropertyChangeListener()
          {
             long sequenceNr = System.currentTimeMillis();

             @Override
             public void propertyChange(PropertyChangeEvent evt)
             {
                Notification notification = new Notification(evt.getPropertyName(), mbeanObjectName, sequenceNr++, System.currentTimeMillis(), evt.getNewValue().toString());
                sendNotification(notification);
             }
          });
       }

       @Override
       public String getStatus()
       {
          return circuitBreaker.status().name();
       }

       @Override
       public int getThreshold()
       {
          return circuitBreaker.threshold();
       }

       @Override
       public double getServiceLevel()
       {
          return circuitBreaker.serviceLevel();
       }

       @Override
       public String getLastErrorMessage()
       {
          return circuitBreaker.lastThrowable() == null ? "" : errorMessage(circuitBreaker.lastThrowable());
       }

       private String errorMessage(Throwable throwable)
       {
          String message = throwable.getMessage();
          if (message == null)
             message = throwable.getClass().getSimpleName();

          if (throwable.getCause() != null)
          {
             return message + ":" + errorMessage(throwable.getCause());
          } else
             return message;
       }

       @Override
       public String getTrippedOn()
       {
          Date trippedOn = circuitBreaker.trippedOn();
          return trippedOn == null ? "" : DateFormat.getDateTimeInstance().format(trippedOn);
       }

       @Override
       public String getEnableOn()
       {
          Date trippedOn = circuitBreaker.enabledOn();
          return trippedOn == null ? "" : DateFormat.getDateTimeInstance().format(trippedOn);
       }

       @Override
       public String turnOn()
       {
          try
          {
             circuitBreaker.turnOn();
             return "Circuit breaker has been turned on";
          } catch (PropertyVetoException e)
          {
             return "Could not turn on circuit breaker:" + getLastErrorMessage();
          }
       }

       @Override
       public void trip()
       {
          circuitBreaker.trip();
       }
    }