/*
 * Copyright (c) 2007, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0, which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.glassfish.gmbal ;

import java.lang.annotation.Documented ;
import java.lang.annotation.Target ;
import java.lang.annotation.ElementType ;
import java.lang.annotation.Retention ;
import java.lang.annotation.RetentionPolicy ;

This annotation defines an attribute in either CompositeData (ManagedData) or 
an open MBean (ManagedObject).  An attribute may be read/write (has a setter
and a getter), read only (only has a getter),
or write only (only has a setter) depending on the declared methods in the class.  
 
A method defines a getter if it returns a non-void type and takes no argument types.
Likewise a method defines a setter if it return void and takes exactly one
argument.  
An id is derived from a method name as follows:

If the method is a getter, and has a name of the form getXXX, the derived
id is xXX (note the initial lower case change).
If the method is a getter with a boolean return type, and has a name of 
the form isXXX, the derived id is xXX
If the method is a setter, and has a name of the form setXXX, the
detived id is xXX.
Otherwise the derived ID is the method name.


In certain cases, a field annotated with @ManagedAttribute 
may also represent a read-only attribute.
The field must be final, and its type must be one of:

A primitive type (boolean, byte, short, char, int, long, float, double)
A primitive type wrapper (Boolean, Byte, Short, Character, Integer, 
Long, Float, Double)
A String
A BigDecimal or BigInteger
A java.util.Date
An ObjectName
An enum (which is translated to its ordinal name)

Any such field can be accessed safely by multiple threads, because its value
cannot change after an instance of the containing class has completed its
constructor.  Note that Date is not truly immutable (it should be!), but it's
one of the Open MBean simple types, so it is included here.
/** This annotation defines an attribute in either CompositeData (ManagedData) or 
 * an open MBean (ManagedObject).  An attribute may be read/write (has a setter
 * and a getter), read only (only has a getter),
 * or write only (only has a setter) depending on the declared methods in the class.  
 * <p> 
 * A method defines a getter if it returns a non-void type and takes no argument types.
 * Likewise a method defines a setter if it return void and takes exactly one
 * argument.  
 * <p>An id is derived from a method name as follows:
 * <ol>
 * <li>If the method is a getter, and has a name of the form getXXX, the derived
 * id is xXX (note the initial lower case change).
 * <li>If the method is a getter with a boolean return type, and has a name of 
 * the form isXXX, the derived id is xXX
 * <li>If the method is a setter, and has a name of the form setXXX, the
 * detived id is xXX.
 * <li>Otherwise the derived ID is the method name.
 * </ol>
 * <p>
 * In certain cases, a field annotated with @ManagedAttribute 
 * may also represent a read-only attribute.
 * The field must be final, and its type must be one of:
 * <ol>
 * <li>A primitive type (boolean, byte, short, char, int, long, float, double)
 * <li>A primitive type wrapper (Boolean, Byte, Short, Character, Integer, 
 * Long, Float, Double)
 * <li>A String
 * <li>A BigDecimal or BigInteger
 * <li>A java.util.Date
 * <li>An ObjectName
 * <li>An enum (which is translated to its ordinal name)
 * </ol>
 * Any such field can be accessed safely by multiple threads, because its value
 * cannot change after an instance of the containing class has completed its
 * constructor.  Note that Date is not truly immutable (it should be!), but it's
 * one of the Open MBean simple types, so it is included here.
 */
@Documented 
@Target({ElementType.METHOD,ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface ManagedAttribute {
    
The id of the attribute.  Defaults to value derived from method name.
Returns:
The id (default "")./** The id of the attribute.  Defaults to value derived from method name.
     * @return The id (default "").
     */
    String id() default "" ;
}