/*
 * @(#)Notification.java	4.40 03/12/19
 * 
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.management;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamField;

import java.util.Date;
import java.util.EventObject;

import java.security.AccessController;
import java.security.PrivilegedAction;

import com.sun.jmx.mbeanserver.GetPropertyAction;

/**
 * <p>The Notification class represents a notification emitted by an
 * MBean.  It contains a reference to the source MBean: if the
 * notification has been forwarded through the MBean server, and the
 * original source of the notification was a reference to the emitting
 * MBean object, then the MBean server replaces it by the MBean's
 * ObjectName.  If the listener has registered directly with the
 * MBean, this is either the object name or a direct reference to the
 * MBean.</p>
 *
 * <p>It is strongly recommended that notification senders use the
 * object name rather than a reference to the MBean object as the
 * source.</p>
 *
 * @since 1.5
 */
public class Notification extends EventObject { 

    // Serialization compatibility stuff:
    // Two serial forms are supported in this class. The selected form depends
    // on system property "jmx.serial.form":
    //  - "1.0" for JMX 1.0
    //  - any other value for JMX 1.1 and higher
    //
    // Serial version for old serial form 
    private static final long oldSerialVersionUID = 1716977971058914352L;
    //
    // Serial version for new serial form 
    private static final long newSerialVersionUID = -7516092053498031989L;
    //
    // Serializable fields in old serial form
    private static final ObjectStreamField[] oldSerialPersistentFields = 
    {
	new ObjectStreamField("message", String.class),
        new ObjectStreamField("sequenceNumber", Long.TYPE),
        new ObjectStreamField("source", Object.class),
        new ObjectStreamField("sourceObjectName", ObjectName.class),
        new ObjectStreamField("timeStamp", Long.TYPE),
        new ObjectStreamField("type", String.class),
        new ObjectStreamField("userData", Object.class)
    };
    //
    // Serializable fields in new serial form
    private static final ObjectStreamField[] newSerialPersistentFields = 
    {
	new ObjectStreamField("message", String.class),
        new ObjectStreamField("sequenceNumber", Long.TYPE),
        new ObjectStreamField("source", Object.class),
        new ObjectStreamField("timeStamp", Long.TYPE),
        new ObjectStreamField("type", String.class),
        new ObjectStreamField("userData", Object.class)
    };
    //
    // Actual serial version and serial form
    private static final long serialVersionUID;
    /**
     * @serialField type String The notification type. 
     *              A string expressed in a dot notation similar to Java properties.
     *              An example of a notification type is network.alarm.router
     * @serialField sequenceNumber long The notification sequence number. 
     *              A serial number which identify particular instance
     *              of notification in the context of the notification source.
     * @serialField timeStamp long The notification timestamp. 
     *              Indicating when the notification was generated
     * @serialField userData Object The notification user data.  
     *              Used for whatever other data the notification
     *              source wishes to communicate to its consumers
     * @serialField message String The notification message.
     * @serialField source Object The object on which the notification initially occurred.
     */
    private static final ObjectStreamField[] serialPersistentFields;
    private static boolean compat = false;  
    static {
	try {
	    PrivilegedAction act = new GetPropertyAction("jmx.serial.form");
	    String form = (String) AccessController.doPrivileged(act);
	    compat = (form != null && form.equals("1.0"));
	} catch (Exception e) {
	    // OK: exception means no compat with 1.0, too bad
	}
	if (compat) {
	    serialPersistentFields = oldSerialPersistentFields;
	    serialVersionUID = oldSerialVersionUID;
	} else {
	    serialPersistentFields = newSerialPersistentFields;
	    serialVersionUID = newSerialVersionUID;
	}
    }
    //
    // END Serialization compatibility stuff

    /**
     * @serial The notification type. 
     *         A string expressed in a dot notation similar to Java properties.
     *         An example of a notification type is network.alarm.router
     */
    private String type;
    
    /**
     * @serial The notification sequence number. 
     *         A serial number which identify particular instance
     *         of notification in the context of the notification source.
     */
    private long sequenceNumber;
    
    /**
     * @serial The notification timestamp. 
     *         Indicating when the notification was generated
     */
    private long timeStamp;

    /**
     * @serial The notification user data.  
     *         Used for whatever other data the notification
     *         source wishes to communicate to its consumers
     */
    private Object userData = null; 

    /**
     * @serial The notification message.
     */
    private String message  = "";
    
    /**
     * <p>This field hides the {@link EventObject#source} field in the
     * parent class to make it non-transient and therefore part of the
     * serialized form.</p>
     *
     * @serial The object on which the notification initially occurred.
     */
    protected Object source = null;
    
    
    /**
     * Creates a Notification object.
     * The notification timeStamp is set to the current date.
     *
     * @param type The notification type.   
     * @param source The notification source.    
     * @param sequenceNumber The notification sequence number within the source object.
     *
     */
    public Notification(String type, Object source, long sequenceNumber) {
        super (source) ;
	this.source = source;
        this.type = type;
        this.sequenceNumber = sequenceNumber ;
        this.timeStamp = (new java.util.Date()).getTime() ;
    } 

    /**
     * Creates a Notification object.
     * The notification timeStamp is set to the current date.
     *
     * @param type The notification type.    
     * @param source The notification source.    
     * @param sequenceNumber The notification sequence number within the source object.    
     * @param message The detailed message.
     *
     */
    public Notification(String type, Object source, long sequenceNumber, String message) {
        super (source) ;
	this.source = source;
        this.type = type;
        this.sequenceNumber = sequenceNumber ;
        this.timeStamp = (new java.util.Date()).getTime() ;
        this.message = message ;
    } 
    
    /**
     * Creates a Notification object.
     *
     * @param type The notification type.    
     * @param source The notification source.    
     * @param sequenceNumber The notification sequence number within the source object.    
     * @param timeStamp The notification emission date.
     *    
     */
    public Notification(String type, Object source, long sequenceNumber, long timeStamp) {
        super (source) ;
	this.source = source;
        this.type = type ;
        this.sequenceNumber = sequenceNumber ;
        this.timeStamp = timeStamp ;
    } 
    
    /**
     * Creates a Notification object.
     *
     * @param type The notification type.    
     * @param source The notification source.    
     * @param sequenceNumber The notification sequence number within the source object.    
     * @param timeStamp The notification emission date.     
     * @param message The detailed message.
     *
     */
    public Notification(String type, Object source, long sequenceNumber, long timeStamp, String message) {
        super (source) ;
	this.source = source;
        this.type = type ;
        this.sequenceNumber = sequenceNumber ;
        this.timeStamp = timeStamp ;
        this.message = message ;
    } 

    /**
     * Sets the source.
     *
     * @param source the new source for this object.
     *
     * @see EventObject#getSource
     */
    public void setSource(Object source) {
	super.source = source;
	this.source = source;
    } 

    /**
     * Get the notification sequence number.
     *
     * @return The notification sequence number within the source object. It's a serial number
     * identifying a particular instance of notification in the context of the notification source.
     * The notification model does not assume that notifications will be received in the same order
     * that they are sent. The sequence number helps listeners to sort received notifications.
     *
     * @see #setSequenceNumber
     */
    public long getSequenceNumber() {
        return sequenceNumber ;
    } 
    
    /**
     * Set the notification sequence number.
     *
     * @param sequenceNumber The notification sequence number within the source object. It is
     * a serial number identifying a particular instance of notification in the
     * context of the notification source.
     *
     * @see #getSequenceNumber
     */
    public void setSequenceNumber(long sequenceNumber) {
        this.sequenceNumber = sequenceNumber;
    } 
    
    /**
     * Get the notification type.
     *
     * @return The notification type. It's a string expressed in a dot notation similar
     * to Java properties. An example of a notification type is network.alarm.router .
     */
    public String getType() {
        return type ;
    } 
    
    /**
     * Get the notification timestamp.
     *
     * @return The notification timestamp.
     *
     * @see #setTimeStamp
     */
    public long getTimeStamp() {
        return timeStamp ;
    } 
    
    /**
     * Set the notification timestamp.
     *
     * @param timeStamp The notification timestamp. It indicates when the notification was generated.
     *
     * @see #getTimeStamp
     */
    public void setTimeStamp(long timeStamp) {
        this.timeStamp = timeStamp;
    } 
    
    /**
     * Get the notification message.
     *
     * @return The message string of this notification object. It contains in a string,
     * which could be the explanation of the notification for displaying to a user
     *
     */
    public String getMessage() {
        return message ;
    } 
    
    /**
     * Get the user data.
     *
     * @return The user data object. It is used for whatever data
     * the notification source wishes to communicate to its consumers.
     *
     * @see #setUserData
     */
    public Object getUserData() {
        return userData ;
    } 
    
    /**
     * Set the user data.
     *
     * @param userData The user data object. It is used for whatever data
     * the notification source wishes to communicate to its consumers.
     *
     * @see #getUserData
     */
    public void setUserData(Object userData) {

        this.userData = userData ;
    } 

    /**
     * Returns a String representation of this notification.
     *
     * @return A String representation of this notification.
     */
    public String toString() {
	return super.toString()+"[type="+type+"][message="+message+"]";
    }

    /**
     * Deserializes a {@link Notification} from an {@link ObjectInputStream}.
     */
    private void readObject(ObjectInputStream in)
	    throws IOException, ClassNotFoundException { 
      // New serial form ignores extra field "sourceObjectName"
      in.defaultReadObject();
      super.source = source;
    }


    /**
     * Serializes a {@link Notification} to an {@link ObjectOutputStream}.
     */
    private void writeObject(ObjectOutputStream out)
	    throws IOException {
	if (compat) {
	    // Serializes this instance in the old serial form
	    //
	    ObjectOutputStream.PutField fields = out.putFields();
	    fields.put("type", type);
	    fields.put("sequenceNumber", sequenceNumber);
	    fields.put("timeStamp", timeStamp);
	    fields.put("userData", userData);
	    fields.put("message", message);
	    fields.put("source", source);
	    out.writeFields();
	} else {
	    // Serializes this instance in the new serial form
	    //
	    out.defaultWriteObject();
	}
    }
}