simpledynamic.java

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/*
 * @(#)file      SimpleDynamic.java
 * @(#)author    Sun Microsystems, Inc.
 * @(#)version   1.1
 * @(#)lastedit  04/01/12
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * Use is subject to license terms.
 */

/**
 * Simple definition of a dynamic MBean, named "SimpleDynamic".
 *
 * The "SimpleDynamic" dynamic MBean shows how to expose for management
 * attributes and operations, at runtime,  by implementing the  
 * "javax.management.DynamicMBean" interface.
 *
 * This MBean exposes for management two attributes and one operation:
 *      - the read/write "State" attribute,
 *      - the read only "NbChanges" attribute,
 *      - the "reset()" operation.
 * It does so by putting this information in an MBeanInfo object that
 * is returned by the getMBeanInfo() method of the DynamicMBean interface.
 *
 * It implements the access to its attributes through the getAttribute(),
 * getAttributes(), setAttribute(), and setAttributes() methods of the
 * DynamicMBean interface.
 *
 * It implements the invocation of its reset() operation through the
 * invoke() method of the DynamicMBean interface.
 * 
 * Note that as "SimpleDynamic" explicitly defines one constructor,
 * this constructor must be public and exposed for management through
 * the MBeanInfo object.
 */

import java.lang.reflect.Constructor;
import java.util.Iterator;
import javax.management.*;

public class SimpleDynamic
    extends NotificationBroadcasterSupport
    implements DynamicMBean {

    /*
     * -----------------------------------------------------
     * CONSTRUCTORS
     * -----------------------------------------------------
     */

    public SimpleDynamic() {
        // Build the management information to be exposed by the dynamic MBean
        //
        buildDynamicMBeanInfo();
    }

    /*
     * -----------------------------------------------------
     * IMPLEMENTATION OF THE DynamicMBean INTERFACE
     * -----------------------------------------------------
     */

    /**
     * Allows the value of the specified attribute of the Dynamic MBean to be
     * obtained.
     */
    public Object getAttribute(String attribute_name) 
        throws AttributeNotFoundException,
               MBeanException,
               ReflectionException {

        // Check attribute_name is not null to avoid NullPointerException
        // later on
        //
        if (attribute_name == null) {
            throw new RuntimeOperationsException(
                  new IllegalArgumentException("Attribute name cannot be null"),
                  "Cannot invoke a getter of " + dClassName +
                  " with null attribute name");
        }
        // Check for a recognized attribute_name and call the corresponding
        // getter
        //
        if (attribute_name.equals("State")) {
            return getState();
        } 
        if (attribute_name.equals("NbChanges")) {
            return getNbChanges();
        }
        // If attribute_name has not been recognized throw an
        // AttributeNotFoundException
        //
        throw new AttributeNotFoundException("Cannot find " +
                                             attribute_name +
                                             " attribute in " +
                                             dClassName);
    }

    /**
     * Sets the value of the specified attribute of the Dynamic MBean.
     */
    public void setAttribute(Attribute attribute) 
        throws AttributeNotFoundException,
               InvalidAttributeValueException,
               MBeanException, 
               ReflectionException {

        // Check attribute is not null to avoid NullPointerException later on
        //
        if (attribute == null) {
            throw new RuntimeOperationsException(
                  new IllegalArgumentException("Attribute cannot be null"), 
                  "Cannot invoke a setter of " + dClassName +
                  " with null attribute");
        }
        String name = attribute.getName();
        Object value = attribute.getValue();
        if (name == null) {
            throw new RuntimeOperationsException(
                  new IllegalArgumentException("Attribute name cannot be null"),
                  "Cannot invoke the setter of " + dClassName +
                  " with null attribute name");
        }
        // Check for a recognized attribute name and call the corresponding
        // setter
        //
        if (name.equals("State")) {
            // if null value, try and see if the setter returns any exception
            if (value == null) {
                try {
                    setState( null );
                } catch (Exception e) {
                    throw new InvalidAttributeValueException(
                              "Cannot set attribute " + name + " to null");
                }
            }
            // if non null value, make sure it is assignable to the attribute
            else {
                try {
                    if (Class.forName("java.lang.String").isAssignableFrom(
                                                          value.getClass())) {
                        setState((String) value);
                    } else {
                        throw new InvalidAttributeValueException(
                                  "Cannot set attribute " + name + " to a " + 
                                  value.getClass().getName() +
                                  " object, String expected");
                    }
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }
            }
        }
        // recognize an attempt to set "NbChanges" attribute (read-only):
        else if (name.equals("NbChanges")) {
            throw new AttributeNotFoundException(
                  "Cannot set attribute " + name + " because it is read-only");
        }
        // unrecognized attribute name:
        else {
            throw new AttributeNotFoundException("Attribute " + name +
                                                 " not found in " +
                                                 this.getClass().getName());
        }
    }

    /**
     * Enables the to get the values of several attributes of the Dynamic MBean.
     */
    public AttributeList getAttributes(String[] attributeNames) {

        // Check attributeNames is not null to avoid NullPointerException
        // later on
        //
        if (attributeNames == null) {
            throw new RuntimeOperationsException(
                new IllegalArgumentException("attributeNames[] cannot be null"),
                "Cannot invoke a getter of " + dClassName);
        }
        AttributeList resultList = new AttributeList();

        // If attributeNames is empty, return an empty result list
        //
        if (attributeNames.length == 0)
            return resultList;
        
        // Build the result attribute list
        //
        for (int i = 0 ; i < attributeNames.length ; i++) {
            try {        
                Object value = getAttribute((String) attributeNames[i]);     
                resultList.add(new Attribute(attributeNames[i],value));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return resultList;
    }

    /**
     * Sets the values of several attributes of the Dynamic MBean, and returns
     * the list of attributes that have been set.
     */
    public AttributeList setAttributes(AttributeList attributes) {

        // Check attributes is not null to avoid NullPointerException later on
        //
        if (attributes == null) {
            throw new RuntimeOperationsException(
                      new IllegalArgumentException(
                                 "AttributeList attributes cannot be null"),
                      "Cannot invoke a setter of " + dClassName);
        }