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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.log4j.jmx;

import java.util.Enumeration;
import java.util.Iterator;
import java.util.Vector;

import javax.management.Attribute;
import javax.management.AttributeList;
import javax.management.DynamicMBean;
import javax.management.InstanceAlreadyExistsException;
import javax.management.InstanceNotFoundException;
import javax.management.JMException;
import javax.management.MBeanRegistration;
import javax.management.MBeanRegistrationException;
import javax.management.MBeanServer;
import javax.management.NotCompliantMBeanException;
import javax.management.ObjectName;
import javax.management.RuntimeOperationsException;

import org.apache.log4j.Logger;
import org.apache.log4j.Appender;

public abstract class AbstractDynamicMBean implements DynamicMBean, MBeanRegistration {

    String dClassName;
    MBeanServer server;
    private final Vector mbeanList = new Vector();

    /**
     * Get MBean name.
     * 
     * @param appender appender, may not be null.
     * @return name.
     * @since 1.2.16
     */
    static protected String getAppenderName(final Appender appender) {
	String name = appender.getName();
	if (name == null || name.trim().length() == 0) {
	    // try to get some form of a name, because null is not allowed (exception), and
	    // empty string certainly isn't useful in JMX..
	    name = appender.toString();
	}
	return name;
    }

    /**
     * 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 (JMException e) {
		e.printStackTrace();
	    } catch (RuntimeException 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);
	}
	AttributeList resultList = new AttributeList();

	// if attributeNames is empty, nothing more to do
	if (attributes.isEmpty())
	    return resultList;

	// for each attribute, try to set it and add to the result list if successfull
	for (Iterator i = attributes.iterator(); i.hasNext();) {
	    Attribute attr = (Attribute) i.next();
	    try {
		setAttribute(attr);
		String name = attr.getName();
		Object value = getAttribute(name);
		resultList.add(new Attribute(name, value));
	    } catch (JMException e) {
		e.printStackTrace();
	    } catch (RuntimeException e) {
		e.printStackTrace();
	    }
	}
	return (resultList);
    }

    protected abstract Logger getLogger();

    public void postDeregister() {
	getLogger().debug("postDeregister is called.");
    }

    public void postRegister(java.lang.Boolean registrationDone) {
    }

    public ObjectName preRegister(MBeanServer server, ObjectName name) {
	getLogger().debug("preRegister called. Server=" + server + ", name=" + name);
	this.server = server;
	return name;
    }

    /**
     * Registers MBean instance in the attached server. Must NOT be called
     * before registration of this instance.
     */
    protected void registerMBean(Object mbean, ObjectName objectName)
	    throws InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException {
	server.registerMBean(mbean, objectName);
	mbeanList.add(objectName);
    }

    /**
     * Performs cleanup for deregistering this MBean. Default implementation
     * unregisters MBean instances which are registered using
     * {@link #registerMBean(Object mbean, ObjectName objectName)}.
     */
    public void preDeregister() {
	getLogger().debug("preDeregister called.");

	Enumeration iterator = mbeanList.elements();
	while (iterator.hasMoreElements()) {
	    ObjectName name = (ObjectName) iterator.nextElement();
	    try {
		server.unregisterMBean(name);
	    } catch (InstanceNotFoundException e) {
		getLogger().warn("Missing MBean " + name.getCanonicalName());
	    } catch (MBeanRegistrationException e) {
		getLogger().warn("Failed unregistering " + name.getCanonicalName());
	    }
	}
    }

}