https://openjdk.java.net/ 
/*
 * Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
/*
 * @author    IBM Corp.
 *
 * Copyright IBM Corp. 1999-2000.  All rights reserved.
 */

package javax.management.modelmbean;

import static com.sun.jmx.defaults.JmxProperties.MODELMBEAN_LOGGER;
import com.sun.jmx.mbeanserver.GetPropertyAction;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamField;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.lang.System.Logger.Level;

import javax.management.Descriptor;
import javax.management.DescriptorKey;
import javax.management.DescriptorAccess;
import javax.management.MBeanAttributeInfo;
import javax.management.RuntimeOperationsException;


The ModelMBeanAttributeInfo object describes an attribute of the ModelMBean.
It is a subclass of MBeanAttributeInfo with the addition of an associated Descriptor
and an implementation of the DescriptorAccess interface.



The fields in the descriptor are defined, but not limited to, the following.
Note that when the Type in this table is Number, a String that is the decimal
representation of a Long can also be used.



ModelMBeanAttributeInfo Fields

NameTypeMeaning


nameString
    Attribute name.


descriptorTypeString
    Must be "attribute".


valueObject
    Current (cached) value for attribute.


defaultObject
    Default value for attribute.


displayNameString
    Name of attribute to be used in displays.


getMethodString
    Name of operation descriptor for get method.


setMethodString
    Name of operation descriptor for set method.


protocolMapDescriptor
    See the section "Protocol Map Support" in the JMX specification
        document.  Mappings must be appropriate for the attribute and entries
        can be updated or augmented at runtime.


persistPolicyString
    One of: OnUpdate|OnTimer|NoMoreOftenThan|OnUnregister|Always|Never.
        See the section "MBean Descriptor Fields" in the JMX specification
        document.


persistPeriodNumber
    Frequency of persist cycle in seconds. Used when persistPolicy is
        "OnTimer" or "NoMoreOftenThan".


currencyTimeLimitNumber
    How long value is valid: <0 never,
        =0 always, >0 seconds.


lastUpdatedTimeStampNumber
    When value was set.


visibilityNumber
    1-4 where 1: always visible, 4: rarely visible.


presentationStringString
    XML formatted string to allow presentation of data.




The default descriptor contains the name, descriptorType and displayName
fields.  The default value of the name and displayName fields is the name of
the attribute.


Note: because of inconsistencies in previous versions of
this specification, it is recommended not to use negative or zero
values for currencyTimeLimit.  To indicate that a
cached value is never valid, omit the
currencyTimeLimit field.  To indicate that it is
always valid, use a very large number for this field.


The serialVersionUID of this class is 6181543027787327345L.

Since:1.5
/**
 * <p>The ModelMBeanAttributeInfo object describes an attribute of the ModelMBean.
 * It is a subclass of MBeanAttributeInfo with the addition of an associated Descriptor
 * and an implementation of the DescriptorAccess interface.</p>
 *
 * <P id="descriptor">
 * The fields in the descriptor are defined, but not limited to, the following.
 * Note that when the Type in this table is Number, a String that is the decimal
 * representation of a Long can also be used.</P>
 *
 * <table class="striped">
 * <caption style="display:none">ModelMBeanAttributeInfo Fields</caption>
 * <tr><th>Name</th><th>Type</th><th>Meaning</th></tr>
 * <tr><td>name</td><td>String</td>
 *     <td>Attribute name.</td></tr>
 * <tr><td>descriptorType</td><td>String</td>
 *     <td>Must be "attribute".</td></tr>
 * <tr id="value-field"><td>value</td><td>Object</td>
 *     <td>Current (cached) value for attribute.</td></tr>
 * <tr><td>default</td><td>Object</td>
 *     <td>Default value for attribute.</td></tr>
 * <tr><td>displayName</td><td>String</td>
 *     <td>Name of attribute to be used in displays.</td></tr>
 * <tr><td>getMethod</td><td>String</td>
 *     <td>Name of operation descriptor for get method.</td></tr>
 * <tr><td>setMethod</td><td>String</td>
 *     <td>Name of operation descriptor for set method.</td></tr>
 * <tr><td>protocolMap</td><td>Descriptor</td>
 *     <td>See the section "Protocol Map Support" in the JMX specification
 *         document.  Mappings must be appropriate for the attribute and entries
 *         can be updated or augmented at runtime.</td></tr>
 * <tr><td>persistPolicy</td><td>String</td>
 *     <td>One of: OnUpdate|OnTimer|NoMoreOftenThan|OnUnregister|Always|Never.
 *         See the section "MBean Descriptor Fields" in the JMX specification
 *         document.</td></tr>
 * <tr><td>persistPeriod</td><td>Number</td>
 *     <td>Frequency of persist cycle in seconds. Used when persistPolicy is
 *         "OnTimer" or "NoMoreOftenThan".</td></tr>
 * <tr><td>currencyTimeLimit</td><td>Number</td>
 *     <td>How long <a href="#value=field">value</a> is valid: &lt;0 never,
 *         =0 always, &gt;0 seconds.</td></tr>
 * <tr><td>lastUpdatedTimeStamp</td><td>Number</td>
 *     <td>When <a href="#value-field">value</a> was set.</td></tr>
 * <tr><td>visibility</td><td>Number</td>
 *     <td>1-4 where 1: always visible, 4: rarely visible.</td></tr>
 * <tr><td>presentationString</td><td>String</td>
 *     <td>XML formatted string to allow presentation of data.</td></tr>
 * </table>
 *
 * <p>The default descriptor contains the name, descriptorType and displayName
 * fields.  The default value of the name and displayName fields is the name of
 * the attribute.</p>
 *
 * <p><b>Note:</b> because of inconsistencies in previous versions of
 * this specification, it is recommended not to use negative or zero
 * values for <code>currencyTimeLimit</code>.  To indicate that a
 * cached value is never valid, omit the
 * <code>currencyTimeLimit</code> field.  To indicate that it is
 * always valid, use a very large number for this field.</p>
 *
 * <p>The <b>serialVersionUID</b> of this class is <code>6181543027787327345L</code>.
 *
 * @since 1.5
 */

@SuppressWarnings("serial")  // serialVersionUID is not constant
public class ModelMBeanAttributeInfo
    extends MBeanAttributeInfo
    implements DescriptorAccess {

    // 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 = 7098036920755973145L;
    //
    // Serial version for new serial form
    private static final long newSerialVersionUID = 6181543027787327345L;
    //
    // Serializable fields in old serial form
    private static final ObjectStreamField[] oldSerialPersistentFields =
    {
      new ObjectStreamField("attrDescriptor", Descriptor.class),
      new ObjectStreamField("currClass", String.class)
    };
    //
    // Serializable fields in new serial form
    private static final ObjectStreamField[] newSerialPersistentFields =
    {
      new ObjectStreamField("attrDescriptor", Descriptor.class)
    };
    //
    // Actual serial version and serial form
    private static final long serialVersionUID;
    
@serialFieldattrDescriptor Descriptor The Descriptor containing the metadata corresponding to this attribute
/**
     * @serialField attrDescriptor Descriptor The {@link Descriptor}
     * containing the metadata corresponding to this attribute
     */
    private static final ObjectStreamField[] serialPersistentFields;
    private static boolean compat = false;
    static {
        try {
            GetPropertyAction act = new GetPropertyAction("jmx.serial.form");
            String form = AccessController.doPrivileged(act);
            compat = (form != null && form.equals("1.0"));
        } catch (Exception e) {
            // OK: No compat with 1.0
        }
        if (compat) {
            serialPersistentFields = oldSerialPersistentFields;
            serialVersionUID = oldSerialVersionUID;
        } else {
            serialPersistentFields = newSerialPersistentFields;
            serialVersionUID = newSerialVersionUID;
        }
    }
    //
    // END Serialization compatibility stuff

        
@serialThe Descriptor containing the metadata corresponding to this attribute
/**
         * @serial The {@link Descriptor} containing the metadata corresponding to
         * this attribute
         */
        private Descriptor attrDescriptor = validDescriptor(null);

        private final static String currClass = "ModelMBeanAttributeInfo";

        
Constructs a ModelMBeanAttributeInfo object with a default descriptor. The Descriptor of the constructed object will include fields contributed by any annotations on the Method objects that contain the DescriptorKey meta-annotation. 
Params:
  • name – The name of the attribute.
  • description – A human readable description of the attribute. Optional.
  • getter – The method used for reading the attribute value.
         May be null if the property is write-only.
  • setter – The method used for writing the attribute value.
         May be null if the attribute is read-only.
Throws:
/**
         * Constructs a ModelMBeanAttributeInfo object with a default
         * descriptor. The {@link Descriptor} of the constructed
         * object will include fields contributed by any annotations
         * on the {@code Method} objects that contain the {@link
         * DescriptorKey} meta-annotation.
         *
         * @param name The name of the attribute.
         * @param description A human readable description of the attribute. Optional.
         * @param getter The method used for reading the attribute value.
         *          May be null if the property is write-only.
         * @param setter The method used for writing the attribute value.
         *          May be null if the attribute is read-only.
         * @exception javax.management.IntrospectionException There is a consistency
         * problem in the definition of this attribute.
         *
         */

        public ModelMBeanAttributeInfo(String name,
                                       String description,
                                       Method getter,
                                       Method setter)
        throws javax.management.IntrospectionException {
                super(name, description, getter, setter);

                if (MODELMBEAN_LOGGER.isLoggable(Level.TRACE)) {
                    MODELMBEAN_LOGGER.log(Level.TRACE,
                            "ModelMBeanAttributeInfo(" +
                            "String,String,Method,Method) " +
                            "Entry " + name);
                }

                attrDescriptor = validDescriptor(null);
                // put getter and setter methods in operations list
                // create default descriptor

        }

        
Constructs a ModelMBeanAttributeInfo object. The Descriptor of the constructed object will include fields contributed by any annotations on the Method objects that contain the DescriptorKey meta-annotation. 
Params:
  • name – The name of the attribute.
  • description – A human readable description of the attribute. Optional.
  • getter – The method used for reading the attribute value.
         May be null if the property is write-only.
  • setter – The method used for writing the attribute value.
         May be null if the attribute is read-only.
  • descriptor – An instance of Descriptor containing the
appropriate metadata for this instance of the Attribute. If
it is null, then a default descriptor will be created.  If
the descriptor does not contain the field "displayName" this field is added
in the descriptor with its default value.
Throws:
  • IntrospectionException – There is a consistency
problem in the definition of this attribute.
  • RuntimeOperationsException – Wraps an
IllegalArgumentException. The descriptor is invalid, or descriptor
field "name" is not equal to name parameter, or descriptor field
"descriptorType" is not equal to "attribute".
/**
         * Constructs a ModelMBeanAttributeInfo object.  The {@link
         * Descriptor} of the constructed object will include fields
         * contributed by any annotations on the {@code Method}
         * objects that contain the {@link DescriptorKey}
         * meta-annotation.
         *
         * @param name The name of the attribute.
         * @param description A human readable description of the attribute. Optional.
         * @param getter The method used for reading the attribute value.
         *          May be null if the property is write-only.
         * @param setter The method used for writing the attribute value.
         *          May be null if the attribute is read-only.
         * @param descriptor An instance of Descriptor containing the
         * appropriate metadata for this instance of the Attribute. If
         * it is null, then a default descriptor will be created.  If
         * the descriptor does not contain the field "displayName" this field is added
         * in the descriptor with its default value.
         * @exception javax.management.IntrospectionException There is a consistency
         * problem in the definition of this attribute.
         * @exception RuntimeOperationsException Wraps an
         * IllegalArgumentException. The descriptor is invalid, or descriptor
         * field "name" is not equal to name parameter, or descriptor field
         * "descriptorType" is not equal to "attribute".
         *
         */

        public ModelMBeanAttributeInfo(String name,
                                       String description,
                                       Method getter,
                                       Method setter,
                                       Descriptor descriptor)
        throws javax.management.IntrospectionException {

                super(name, description, getter, setter);
                // put getter and setter methods in operations list
                if (MODELMBEAN_LOGGER.isLoggable(Level.TRACE)) {
                    MODELMBEAN_LOGGER.log(Level.TRACE,
                            "ModelMBeanAttributeInfo(" +
                            "String,String,Method,Method,Descriptor) " +
                            "Entry " + name);
                }
                attrDescriptor = validDescriptor(descriptor);
        }

        
Constructs a ModelMBeanAttributeInfo object with a default descriptor.

Params:
  • name – The name of the attribute
  • type – The type or class name of the attribute
  • description – A human readable description of the attribute.
  • isReadable – True if the attribute has a getter method, false otherwise.
  • isWritable – True if the attribute has a setter method, false otherwise.
  • isIs – True if the attribute has an "is" getter, false otherwise.
/**
         * Constructs a ModelMBeanAttributeInfo object with a default descriptor.
         *
         * @param name The name of the attribute
         * @param type The type or class name of the attribute
         * @param description A human readable description of the attribute.
         * @param isReadable True if the attribute has a getter method, false otherwise.
         * @param isWritable True if the attribute has a setter method, false otherwise.
         * @param isIs True if the attribute has an "is" getter, false otherwise.
         *
         */
        public ModelMBeanAttributeInfo(String name,
                                       String type,
                                       String description,
                                       boolean isReadable,
                                       boolean isWritable,
                                       boolean isIs)
    {

                super(name, type, description, isReadable, isWritable, isIs);
                // create default descriptor
                if (MODELMBEAN_LOGGER.isLoggable(Level.TRACE)) {
                    MODELMBEAN_LOGGER.log(Level.TRACE,
                            ModelMBeanAttributeInfo.class.getName(),
                            "ModelMBeanAttributeInfo(" +
                            "String,String,String,boolean,boolean,boolean)",
                            "Entry", name);
                }
                attrDescriptor = validDescriptor(null);
        }

        
Constructs a ModelMBeanAttributeInfo object.

Params:
  • name – The name of the attribute
  • type – The type or class name of the attribute
  • description – A human readable description of the attribute.
  • isReadable – True if the attribute has a getter method, false otherwise.
  • isWritable – True if the attribute has a setter method, false otherwise.
  • isIs – True if the attribute has an "is" getter, false otherwise.
  • descriptor – An instance of Descriptor containing the
appropriate metadata for this instance of the Attribute. If
it is null then a default descriptor will be created.  If
the descriptor does not contain the field "displayName" this field
is added in the descriptor with its default value.
Throws:
  • RuntimeOperationsException – Wraps an
IllegalArgumentException. The descriptor is invalid, or descriptor
field "name" is not equal to name parameter, or descriptor field
"descriptorType" is not equal to "attribute".
/**
         * Constructs a ModelMBeanAttributeInfo object.
         *
         * @param name The name of the attribute
         * @param type The type or class name of the attribute
         * @param description A human readable description of the attribute.
         * @param isReadable True if the attribute has a getter method, false otherwise.
         * @param isWritable True if the attribute has a setter method, false otherwise.
         * @param isIs True if the attribute has an "is" getter, false otherwise.
         * @param descriptor An instance of Descriptor containing the
         * appropriate metadata for this instance of the Attribute. If
         * it is null then a default descriptor will be created.  If
         * the descriptor does not contain the field "displayName" this field
         * is added in the descriptor with its default value.
         * @exception RuntimeOperationsException Wraps an
         * IllegalArgumentException. The descriptor is invalid, or descriptor
         * field "name" is not equal to name parameter, or descriptor field
         * "descriptorType" is not equal to "attribute".
         *
         */
        public ModelMBeanAttributeInfo(String name,
                                       String type,
                                       String description,
                                       boolean isReadable,
                                       boolean isWritable,
                                       boolean isIs,
                                       Descriptor descriptor)
        {
                super(name, type, description, isReadable, isWritable, isIs);
                if (MODELMBEAN_LOGGER.isLoggable(Level.TRACE)) {
                    MODELMBEAN_LOGGER.log(Level.TRACE,
                            "ModelMBeanAttributeInfo(String,String,String," +
                            "boolean,boolean,boolean,Descriptor)" +
                            "Entry " + name);
                }
                attrDescriptor = validDescriptor(descriptor);
        }

        
Constructs a new ModelMBeanAttributeInfo object from this
ModelMBeanAttributeInfo Object.  A default descriptor will
be created.

Params:
  • inInfo – the ModelMBeanAttributeInfo to be duplicated
/**
         * Constructs a new ModelMBeanAttributeInfo object from this
         * ModelMBeanAttributeInfo Object.  A default descriptor will
         * be created.
         *
         * @param inInfo the ModelMBeanAttributeInfo to be duplicated
         */

        public ModelMBeanAttributeInfo(ModelMBeanAttributeInfo inInfo)
        {
                super(inInfo.getName(),
                          inInfo.getType(),
                          inInfo.getDescription(),
                          inInfo.isReadable(),
                          inInfo.isWritable(),
                          inInfo.isIs());
                if (MODELMBEAN_LOGGER.isLoggable(Level.TRACE)) {
                    MODELMBEAN_LOGGER.log(Level.TRACE,
                            "ModelMBeanAttributeInfo(ModelMBeanAttributeInfo) " +
                            "Entry");
                }
                Descriptor newDesc = inInfo.getDescriptor();
                attrDescriptor = validDescriptor(newDesc);
        }

        
Gets a copy of the associated Descriptor for the
ModelMBeanAttributeInfo.

See Also:
Returns:Descriptor associated with the
ModelMBeanAttributeInfo object.
/**
         * Gets a copy of the associated Descriptor for the
         * ModelMBeanAttributeInfo.
         *
         * @return Descriptor associated with the
         * ModelMBeanAttributeInfo object.
         *
         * @see #setDescriptor
         */

        public Descriptor getDescriptor() {
            if (MODELMBEAN_LOGGER.isLoggable(Level.TRACE)) {
                MODELMBEAN_LOGGER.log(Level.TRACE, "Entry");
            }
                if (attrDescriptor == null) {
                    attrDescriptor = validDescriptor(null);
                }
                return((Descriptor)attrDescriptor.clone());
        }


        
Sets associated Descriptor (full replace) for the
ModelMBeanAttributeDescriptor.  If the new Descriptor is
null, then the associated Descriptor reverts to a default
descriptor.  The Descriptor is validated before it is
assigned.  If the new Descriptor is invalid, then a
RuntimeOperationsException wrapping an
IllegalArgumentException is thrown.

Params:
  • inDescriptor – replaces the Descriptor associated with the
ModelMBeanAttributeInfo
Throws:
See Also:
/**
        * Sets associated Descriptor (full replace) for the
        * ModelMBeanAttributeDescriptor.  If the new Descriptor is
        * null, then the associated Descriptor reverts to a default
        * descriptor.  The Descriptor is validated before it is
        * assigned.  If the new Descriptor is invalid, then a
        * RuntimeOperationsException wrapping an
        * IllegalArgumentException is thrown.
        * @param inDescriptor replaces the Descriptor associated with the
        * ModelMBeanAttributeInfo
        *
        * @exception RuntimeOperationsException Wraps an
        * IllegalArgumentException for an invalid Descriptor
        *
        * @see #getDescriptor
        */
        public void setDescriptor(Descriptor inDescriptor) {
            attrDescriptor =  validDescriptor(inDescriptor);
        }

        
Creates and returns a new ModelMBeanAttributeInfo which is a duplicate of this ModelMBeanAttributeInfo.

Throws:
  • RuntimeOperationsException – for illegal value for
field Names or field Values.  If the descriptor construction
fails for any reason, this exception will be thrown.
/**
        * Creates and returns a new ModelMBeanAttributeInfo which is a duplicate of this ModelMBeanAttributeInfo.
        *
        * @exception RuntimeOperationsException for illegal value for
        * field Names or field Values.  If the descriptor construction
        * fails for any reason, this exception will be thrown.
        */

        @Override
        public Object clone()
        {
            if (MODELMBEAN_LOGGER.isLoggable(Level.TRACE)) {
                MODELMBEAN_LOGGER.log(Level.TRACE, "Entry");
            }
                return(new ModelMBeanAttributeInfo(this));
        }

        
Returns a human-readable version of the
ModelMBeanAttributeInfo instance.

/**
        * Returns a human-readable version of the
        * ModelMBeanAttributeInfo instance.
        */
        @Override
        public String toString()
        {
            return
                "ModelMBeanAttributeInfo: " + this.getName() +
                " ; Description: " + this.getDescription() +
                " ; Types: " + this.getType() +
                " ; isReadable: " + this.isReadable() +
                " ; isWritable: " + this.isWritable() +
                " ; Descriptor: " + this.getDescriptor();
        }


        
Clones the passed in Descriptor, sets default values, and checks for validity.
If the Descriptor is invalid (for instance by having the wrong "name"),
this indicates programming error and a RuntimeOperationsException will be thrown.
The following fields will be defaulted if they are not already set:
displayName=this.getName(),name=this.getName(),descriptorType = "attribute"

Params:
  • in – Descriptor to be checked, or null which is equivalent to
an empty Descriptor.
Throws:
/**
         * Clones the passed in Descriptor, sets default values, and checks for validity.
         * If the Descriptor is invalid (for instance by having the wrong "name"),
         * this indicates programming error and a RuntimeOperationsException will be thrown.
         *
         * The following fields will be defaulted if they are not already set:
         * displayName=this.getName(),name=this.getName(),descriptorType = "attribute"
         *
         * @param in Descriptor to be checked, or null which is equivalent to
         * an empty Descriptor.
         * @exception RuntimeOperationsException if Descriptor is invalid
         */
        private Descriptor validDescriptor(final Descriptor in) throws RuntimeOperationsException {

            Descriptor clone;
            boolean defaulted = (in == null);
            if (defaulted) {
                clone = new DescriptorSupport();
                MODELMBEAN_LOGGER.log(Level.TRACE, "Null Descriptor, creating new.");
            } else {
                clone = (Descriptor) in.clone();
            }

            //Setting defaults.
            if (defaulted && clone.getFieldValue("name")==null) {
                clone.setField("name", this.getName());
                MODELMBEAN_LOGGER.log(Level.TRACE, "Defaulting Descriptor name to " + this.getName());
            }
            if (defaulted && clone.getFieldValue("descriptorType")==null) {
                clone.setField("descriptorType", "attribute");
                MODELMBEAN_LOGGER.log(Level.TRACE, "Defaulting descriptorType to \"attribute\"");
            }
            if (clone.getFieldValue("displayName") == null) {
                clone.setField("displayName",this.getName());
                MODELMBEAN_LOGGER.log(Level.TRACE, "Defaulting Descriptor displayName to " + this.getName());
            }

            //Checking validity
            if (!clone.isValid()) {
                 throw new RuntimeOperationsException(new IllegalArgumentException("Invalid Descriptor argument"),
                    "The isValid() method of the Descriptor object itself returned false,"+
                    "one or more required fields are invalid. Descriptor:" + clone.toString());
            }
            if (!getName().equalsIgnoreCase((String)clone.getFieldValue("name"))) {
                    throw new RuntimeOperationsException(new IllegalArgumentException("Invalid Descriptor argument"),
                    "The Descriptor \"name\" field does not match the object described. " +
                     " Expected: "+ this.getName() + " , was: " + clone.getFieldValue("name"));
            }

            if (!"attribute".equalsIgnoreCase((String)clone.getFieldValue("descriptorType"))) {
                     throw new RuntimeOperationsException(new IllegalArgumentException("Invalid Descriptor argument"),
                    "The Descriptor \"descriptorType\" field does not match the object described. " +
                     " Expected: \"attribute\" ," + " was: " + clone.getFieldValue("descriptorType"));
            }

            return clone;
        }


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


    /**
     * Serializes a {@link ModelMBeanAttributeInfo} 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("attrDescriptor", attrDescriptor);
        fields.put("currClass", currClass);
        out.writeFields();
      }
      else
      {
        // Serializes this instance in the new serial form
        //
        out.defaultWriteObject();
      }
    }

}