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/*
 * @author    IBM Corp.
 *
 * Copyright IBM Corp. 1999-2000.  All rights reserved.
 */

package javax.management;

import java.io.Serializable;

// Javadoc imports:
import java.lang.management.MemoryUsage;
import java.util.Arrays;
import java.util.Locale;
import java.util.ResourceBundle;
import javax.management.openmbean.CompositeData;
import javax.management.openmbean.OpenMBeanAttributeInfoSupport;
import javax.management.openmbean.OpenMBeanOperationInfoSupport;
import javax.management.openmbean.OpenMBeanParameterInfoSupport;
import javax.management.openmbean.OpenType;


Additional metadata for a JMX element. A Descriptor is associated with a MBeanInfo, MBeanAttributeInfo, etc. It consists of a collection of fields. A field is a name and an associated value.


Field names are not case-sensitive. The names descriptorType, descriptortype, and DESCRIPTORTYPE are all equivalent. However, the case that was used when the field was first set is preserved in the result of the getFields and getFieldNames methods.


Not all field names and values are predefined.
New fields can be defined and added by any program.


A descriptor can be mutable or immutable.
An immutable descriptor, once created, never changes.
The Descriptor methods that could modify the contents of the descriptor will throw an exception for an immutable descriptor. Immutable descriptors are usually instances of ImmutableDescriptor or a subclass. Mutable descriptors are usually instances of DescriptorSupport or a subclass. 
Certain fields are used by the JMX implementation.  This means
either that the presence of the field may change the behavior of
the JMX API or that the field may be set in descriptors returned by
the JMX API.  These fields appear in italics in the table below, and each one has a corresponding constant in the JMX class. For example, the field defaultValue is represented by the constant JMX.DEFAULT_VALUE_FIELD.


Certain other fields have conventional meanings described in the
table below but they are not required to be understood or set by
the JMX implementation.


Field names defined by the JMX specification in this and all future versions will never contain a period (.). Users can safely create their own fields by including a period in the name and be sure that these names will not collide with any future version of the JMX API. It is recommended to follow the Java package naming convention to avoid collisions between field names from different origins. For example, a field created by example.com might have the name com.example.interestLevel.


Note that the values in the defaultValue, 
legalValues, maxValue, and minValue fields should be consistent with the type returned by the getType() method for the associated MBeanAttributeInfo or 
MBeanParameterInfo. For MXBeans, this means that they should be of the mapped Java type, called opendata(J) in the MXBean type mapping rules.



Descriptor Fields


Name
    Type
    Used in
    Meaning




defaultValueObject
MBeanAttributeInfo
MBeanParameterInfo		
Default value for an attribute or parameter. See openmbean.

deprecatedStringAny
An indication that this element of the information model is no
longer recommended for use.  A set of MBeans defined by an
application is collectively called an information model. The convention is for the value of this field to contain a string that is the version of the model in which the element was first deprecated, followed by a space, followed by an explanation of the deprecation, for example "1.3 Replaced by the Capacity
attribute".

descriptionResource

BundleBaseName		StringAny
The base name for the ResourceBundle in which the key given in the descriptionResourceKey field can be found, for example "com.example.myapp.MBeanResources". The meaning of this field is defined by this specification but the field is not set or used by the JMX API itself.

descriptionResourceKey
StringAny
A resource key for the description of this element. In conjunction with the descriptionResourceBundleBaseName, this can be used to find a localized version of the description. The meaning of this field is defined by this specification but the field is not set or used by the JMX API itself.

enabledString
MBeanAttributeInfo
MBeanNotificationInfo
MBeanOperationInfo		
The string "true" or "false" according as this item is enabled. When an attribute or operation is not enabled, it exists but cannot currently be accessed. A user interface might present it as a greyed-out item. For example, an attribute might only be meaningful after the start() method of an MBean has been called, and is otherwise disabled. Likewise, a notification might be disabled if it cannot currently be emitted but could be in other circumstances.

exceptionsString[]
MBeanAttributeInfo, MBeanConstructorInfo, MBeanOperationInfo
The class names of the exceptions that can be thrown when invoking a
constructor or operation, or getting an attribute. The meaning of this field
is defined by this specification but the field is not set or used by the
JMX API itself. Exceptions thrown when
setting an attribute are specified by the field
setExceptions.

immutableInfoString
MBeanInfo
The string "true" or "false" according as this MBean's MBeanInfo is immutable.  When this field is true,
the MBeanInfo for the given MBean is guaranteed not to change over
the lifetime of the MBean.  Hence, a client can read it once and
cache the read value.  When this field is false or absent, there is
no such guarantee, although that does not mean that the MBeanInfo
will necessarily change.  See also the "jmx.mbean.info.changed"
notification.

infoTimeoutString
Long		MBeanInfo
The time in milli-seconds that the MBeanInfo can reasonably be expected to be unchanged. The value can be a Long or a decimal string. This provides a hint from a DynamicMBean or any MBean that does not define immutableInfo as true that the MBeanInfo is not likely to change within this period and therefore can be cached. When this field is missing or has the value zero, it is not recommended to cache the MBeanInfo unless it has the immutableInfo set to true or it has "jmx.mbean.info.changed" in its MBeanNotificationInfo array.


interfaceClassName
StringMBeanInfo
The Java interface name for a Standard MBean or MXBean, as returned by Class.getName(). A Standard MBean or MXBean registered directly in the MBean Server or created using the StandardMBean class will have this field in its MBeanInfo Descriptor.

legalValues
Set<?>MBeanAttributeInfo
MBeanParameterInfo		
Legal values for an attribute or parameter. See openmbean.

locale
StringAny
The locale of the description in this MBeanInfo, MBeanAttributeInfo, etc, as returned by Locale.toString().

maxValueObject
MBeanAttributeInfo
MBeanParameterInfo		
Maximum legal value for an attribute or parameter. See openmbean.

metricTypeString
MBeanAttributeInfo
MBeanOperationInfo		
The type of a metric, one of the strings "counter" or "gauge".
A metric is a measurement exported by an MBean, usually an
attribute but sometimes the result of an operation.  A metric that
is a counter has a value that never decreases except by
being reset to a starting value.  Counter metrics are almost always
non-negative integers.  An example might be the number of requests
received.  A metric that is a gauge has a numeric value
that can increase or decrease.  Examples might be the number of
open connections or a cache hit rate or a temperature reading.

minValueObject
MBeanAttributeInfo
MBeanParameterInfo		
Minimum legal value for an attribute or parameter. See openmbean.

mxbeanString
MBeanInfo
The string "true" or "false" according as this MBean is an MXBean. A Standard MBean or MXBean registered directly with the MBean Server or created using the StandardMBean class will have this field in its MBeanInfo Descriptor.

openTypeOpenType
MBeanAttributeInfo
MBeanOperationInfo
MBeanParameterInfo		

The Open Type of this element. In the case of 
MBeanAttributeInfo and MBeanParameterInfo, this is the Open Type of the attribute or parameter. In the case of 
MBeanOperationInfo, it is the Open Type of the return value. This field is set in the Descriptor for all instances of OpenMBeanAttributeInfoSupport, OpenMBeanOperationInfoSupport, and OpenMBeanParameterInfoSupport. It is also set for attributes, operations, and parameters of MXBeans.


This field can be set for an MBeanNotificationInfo, in which case it indicates the Open Type that the user data will have.


originalTypeString
MBeanAttributeInfo
MBeanOperationInfo
MBeanParameterInfo		

The original Java type of this element as it appeared in the MXBean interface method that produced this 
MBeanAttributeInfo (etc). For example, a method
 public
 MemoryUsage getHeapMemoryUsage();
 in an MXBean interface defines an attribute called 
HeapMemoryUsage of type CompositeData. The 
originalType field in the Descriptor for this attribute will have the value "java.lang.management.MemoryUsage". 
The format of this string is described in the section Type Names of the MXBean
specification.


setExceptionsString[]
MBeanAttributeInfo
The class names of the exceptions that can be thrown when setting
an attribute. The meaning of this field
is defined by this specification but the field is not set or used by the
JMX API itself.  Exceptions thrown when getting an attribute are specified
by the field exceptions.

severityString
Integer		
MBeanNotificationInfo
The severity of this notification. It can be 0 to mean unknown severity or a value from 1 to 6 representing decreasing levels of severity. It can be represented as a decimal string or an Integer.

sinceStringAny
The version of the information model in which this element
was introduced.  A set of MBeans defined by an application is
collectively called an information model. The application may also define versions of this model, and use the "since" field to record the version in which an element first appeared.

unitsString
MBeanAttributeInfo
MBeanParameterInfo
MBeanOperationInfo		
The units in which an attribute, parameter, or operation return value is measured, for example "bytes" or 
"seconds".





Some additional fields are defined by Model MBeans.  See the
information for ModelMBeanInfo,
ModelMBeanAttributeInfo,
ModelMBeanConstructorInfo,
ModelMBeanNotificationInfo, and
ModelMBeanOperationInfo, as
well as the chapter "Model MBeans" of the JMX
Specification.  The following table summarizes these fields.  Note
that when the Type in this table is Number, a String that is the decimal
representation of a Long can also be used.


Nothing prevents the use of these fields in MBeans that are not Model
MBeans.  The displayName, severity, and visibility fields are of
interest outside Model MBeans, for example.  But only Model MBeans have
a predefined behavior for these fields.



ModelMBean Fields


Name
    Type
    Used in
    Meaning




classStringModelMBeanOperationInfo
    Class where method is defined (fully qualified).


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


defaultObjectModelMBeanAttributeInfo
    Default value for attribute.


descriptorTypeStringAny
    Type of descriptor, "mbean", "attribute", "constructor", "operation",
        or "notification".


displayNameStringAny
    Human readable name of this item.


exportStringModelMBeanInfo
    Name to be used to export/expose this MBean so that it is
        findable by other JMX Agents.


getMethodStringModelMBeanAttributeInfo
    Name of operation descriptor for get method.


lastUpdatedTimeStampNumber
    ModelMBeanAttributeInfo
ModelMBeanOperationInfo		
    When value was set.


logStringModelMBeanInfo
ModelMBeanNotificationInfo		
    t or T: log all notifications, f or F: log no notifications.


logFileStringModelMBeanInfo
ModelMBeanNotificationInfo		
    Fully qualified filename to log events to.


messageIDStringModelMBeanNotificationInfo
    Unique key for message text (to allow translation, analysis).


messageTextStringModelMBeanNotificationInfo
    Text of notification.


nameStringAny
    Name of this item.


persistFileStringModelMBeanInfo
    File name into which the MBean should be persisted.


persistLocationStringModelMBeanInfo
    The fully qualified directory name where the MBean should be
        persisted (if appropriate).


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


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


presentationStringStringAny
    XML formatted string to allow presentation of data.


protocolMapDescriptorModelMBeanAttributeInfo
    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.


roleString
    ModelMBeanConstructorInfo
ModelMBeanOperationInfo		
    One of "constructor", "operation", "getter", or "setter".


setMethodStringModelMBeanAttributeInfo
    Name of operation descriptor for set method.


severityNumber
    ModelMBeanNotificationInfo
    0-6 where 0: unknown; 1: non-recoverable;
        2: critical, failure; 3: major, severe;
        4: minor, marginal, error; 5: warning;
        6: normal, cleared, informative


targetObjectObjectModelMBeanOperationInfo
    Object on which to execute this method.


targetTypeStringModelMBeanOperationInfo
    type of object reference for targetObject. Can be:
        ObjectReference | Handle | EJBHandle | IOR | RMIReference.


valueObject
    ModelMBeanAttributeInfo
ModelMBeanOperationInfo		
    Current (cached) value for attribute or operation.


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





Since:1.5
/**
 * <p>Additional metadata for a JMX element.  A {@code Descriptor}
 * is associated with a {@link MBeanInfo}, {@link MBeanAttributeInfo}, etc.
 * It consists of a collection of fields.  A field is a name and an
 * associated value.</p>
 *
 * <p>Field names are not case-sensitive.  The names {@code descriptorType},
 * {@code descriptortype}, and {@code DESCRIPTORTYPE} are all equivalent.
 * However, the case that was used when the field was first set is preserved
 * in the result of the {@link #getFields} and {@link #getFieldNames}
 * methods.</p>
 *
 * <p>Not all field names and values are predefined.
 * New fields can be defined and added by any program.</p>
 *
 * <p>A descriptor can be mutable or immutable.
 * An immutable descriptor, once created, never changes.
 * The <code>Descriptor</code> methods that could modify the contents
 * of the descriptor will throw an exception
 * for an immutable descriptor.  Immutable descriptors are usually
 * instances of {@link ImmutableDescriptor} or a subclass.  Mutable
 * descriptors are usually instances of
 * {@link javax.management.modelmbean.DescriptorSupport} or a subclass.
 *
 * <p>Certain fields are used by the JMX implementation.  This means
 * either that the presence of the field may change the behavior of
 * the JMX API or that the field may be set in descriptors returned by
 * the JMX API.  These fields appear in <i>italics</i> in the table
 * below, and each one has a corresponding constant in the {@link JMX}
 * class.  For example, the field {@code defaultValue} is represented
 * by the constant {@link JMX#DEFAULT_VALUE_FIELD}.</p>
 *
 * <p>Certain other fields have conventional meanings described in the
 * table below but they are not required to be understood or set by
 * the JMX implementation.</p>
 *
 * <p>Field names defined by the JMX specification in this and all
 * future versions will never contain a period (.).  Users can safely
 * create their own fields by including a period in the name and be
 * sure that these names will not collide with any future version of
 * the JMX API.  It is recommended to follow the Java package naming
 * convention to avoid collisions between field names from different
 * origins.  For example, a field created by {@code example.com} might
 * have the name {@code com.example.interestLevel}.</p>
 *
 * <p>Note that the values in the {@code defaultValue}, {@code
 * legalValues}, {@code maxValue}, and {@code minValue} fields should
 * be consistent with the type returned by the {@code getType()}
 * method for the associated {@code MBeanAttributeInfo} or {@code
 * MBeanParameterInfo}.  For MXBeans, this means that they should be
 * of the mapped Java type, called <em>opendata</em>(J) in the <a
 * href="MXBean.html#mapping-rules">MXBean type mapping rules</a>.</p>
 *
 * <table class="striped">
 * <caption style="display:none">Descriptor Fields</caption>
 * <thead>
 * <tr><th scope="col">Name</th>
 *     <th scope="col">Type</th>
 *     <th scope="col">Used in</th>
 *     <th scope="col">Meaning</th></tr>
 * </thead>
 *
 * <tbody style="text-align:left">
 * <tr id="defaultValue"><th scope="row"><i>defaultValue</i><td>Object</td>
 * <td>MBeanAttributeInfo<br>MBeanParameterInfo</td>
 *
 * <td>Default value for an attribute or parameter.  See
 * {@link javax.management.openmbean}.</td>
 *
 * <tr><th scope="row">deprecated</th><td>String</td><td>Any</td>
 *
 * <td>An indication that this element of the information model is no
 * longer recommended for use.  A set of MBeans defined by an
 * application is collectively called an <em>information model</em>.
 * The convention is for the value of this field to contain a string
 * that is the version of the model in which the element was first
 * deprecated, followed by a space, followed by an explanation of the
 * deprecation, for example {@code "1.3 Replaced by the Capacity
 * attribute"}.</td>
 *
 * <tr><th scope="row" id="descriptionResourceBundleBaseName">descriptionResource<br>
 * BundleBaseName</th><td>String</td><td>Any</td>
 *
 * <td>The base name for the {@link ResourceBundle} in which the key given in
 * the {@code descriptionResourceKey} field can be found, for example
 * {@code "com.example.myapp.MBeanResources"}.  The meaning of this
 * field is defined by this specification but the field is not set or
 * used by the JMX API itself.</td>
 *
 * <tr><th scope="row" id="descriptionResourceKey">descriptionResourceKey</th>
 * <td>String</td><td>Any</td>
 *
 * <td>A resource key for the description of this element.  In
 * conjunction with the {@code descriptionResourceBundleBaseName},
 * this can be used to find a localized version of the description.
 * The meaning of this field is defined by this specification but the
 * field is not set or used by the JMX API itself.</td>
 *
 * <tr><th scope="row">enabled</th><td>String</td>
 * <td>MBeanAttributeInfo<br>MBeanNotificationInfo<br>MBeanOperationInfo</td>
 *
 * <td>The string {@code "true"} or {@code "false"} according as this
 * item is enabled.  When an attribute or operation is not enabled, it
 * exists but cannot currently be accessed.  A user interface might
 * present it as a greyed-out item.  For example, an attribute might
 * only be meaningful after the {@code start()} method of an MBean has
 * been called, and is otherwise disabled.  Likewise, a notification
 * might be disabled if it cannot currently be emitted but could be in
 * other circumstances.</td>
 *
 * <tr id="exceptions"><th scope="row">exceptions<td>String[]</td>
 * <td>MBeanAttributeInfo, MBeanConstructorInfo, MBeanOperationInfo</td>
 *
 * <td>The class names of the exceptions that can be thrown when invoking a
 * constructor or operation, or getting an attribute. The meaning of this field
 * is defined by this specification but the field is not set or used by the
 * JMX API itself. Exceptions thrown when
 * setting an attribute are specified by the field
 * <a href="#setExceptions">{@code setExceptions}</a>.
 *
 * <tr id="immutableInfo"><th scope="row"><i>immutableInfo</i><td>String</td>
 * <td>MBeanInfo</td>
 *
 * <td>The string {@code "true"} or {@code "false"} according as this
 * MBean's MBeanInfo is <em>immutable</em>.  When this field is true,
 * the MBeanInfo for the given MBean is guaranteed not to change over
 * the lifetime of the MBean.  Hence, a client can read it once and
 * cache the read value.  When this field is false or absent, there is
 * no such guarantee, although that does not mean that the MBeanInfo
 * will necessarily change.  See also the <a
 * href="MBeanInfo.html#info-changed">{@code "jmx.mbean.info.changed"}</a>
 * notification.</td>
 *
 * <tr id="infoTimeout"><th scope="row">infoTimeout</th><td>String<br>Long</td><td>MBeanInfo</td>
 *
 * <td>The time in milli-seconds that the MBeanInfo can reasonably be
 * expected to be unchanged.  The value can be a {@code Long} or a
 * decimal string.  This provides a hint from a DynamicMBean or any
 * MBean that does not define {@code immutableInfo} as {@code true}
 * that the MBeanInfo is not likely to change within this period and
 * therefore can be cached.  When this field is missing or has the
 * value zero, it is not recommended to cache the MBeanInfo unless it
 * has the {@code immutableInfo} set to {@code true} or it has <a
 * href="MBeanInfo.html#info-changed">{@code "jmx.mbean.info.changed"}</a> in
 * its {@link MBeanNotificationInfo} array.</td></tr>
 *
 * <tr id="interfaceClassName"><th scope="row"><i>interfaceClassName</i></th>
 * <td>String</td><td>MBeanInfo</td>
 *
 * <td>The Java interface name for a Standard MBean or MXBean, as
 * returned by {@link Class#getName()}.  A Standard MBean or MXBean
 * registered directly in the MBean Server or created using the {@link
 * StandardMBean} class will have this field in its MBeanInfo
 * Descriptor.</td>
 *
 * <tr id="legalValues"><th scope="row"><i>legalValues</i></th>
 * <td>{@literal Set<?>}</td><td>MBeanAttributeInfo<br>MBeanParameterInfo</td>
 *
 * <td>Legal values for an attribute or parameter.  See
 * {@link javax.management.openmbean}.</td>
 *
 * <tr id="locale"><th scope="row">locale</th>
 * <td>String</td><td>Any</td>
 *
 * <td>The {@linkplain Locale locale} of the description in this
 * {@code MBeanInfo}, {@code MBeanAttributeInfo}, etc, as returned
 * by {@link Locale#toString()}.</td>
 *
 * <tr id="maxValue"><th scope="row"><i>maxValue</i><td>Object</td>
 * <td>MBeanAttributeInfo<br>MBeanParameterInfo</td>
 *
 * <td>Maximum legal value for an attribute or parameter.  See
 * {@link javax.management.openmbean}.</td>
 *
 * <tr id="metricType"><th scope="row">metricType</th><td>String</td>
 * <td>MBeanAttributeInfo<br>MBeanOperationInfo</td>
 *
 * <td>The type of a metric, one of the strings "counter" or "gauge".
 * A metric is a measurement exported by an MBean, usually an
 * attribute but sometimes the result of an operation.  A metric that
 * is a <em>counter</em> has a value that never decreases except by
 * being reset to a starting value.  Counter metrics are almost always
 * non-negative integers.  An example might be the number of requests
 * received.  A metric that is a <em>gauge</em> has a numeric value
 * that can increase or decrease.  Examples might be the number of
 * open connections or a cache hit rate or a temperature reading.
 *
 * <tr id="minValue"><th scope="row"><i>minValue</i><td>Object</td>
 * <td>MBeanAttributeInfo<br>MBeanParameterInfo</td>
 *
 * <td>Minimum legal value for an attribute or parameter.  See
 * {@link javax.management.openmbean}.</td>
 *
 * <tr id="mxbean"><th scope="row"><i>mxbean</i><td>String</td>
 * <td>MBeanInfo</td>
 *
 * <td>The string {@code "true"} or {@code "false"} according as this
 * MBean is an {@link MXBean}.  A Standard MBean or MXBean registered
 * directly with the MBean Server or created using the {@link
 * StandardMBean} class will have this field in its MBeanInfo
 * Descriptor.</td>
 *
 * <tr id="openType"><th scope="row"><i>openType</i><td>{@link OpenType}</td>
 * <td>MBeanAttributeInfo<br>MBeanOperationInfo<br>MBeanParameterInfo</td>
 *
 * <td><p>The Open Type of this element.  In the case of {@code
 * MBeanAttributeInfo} and {@code MBeanParameterInfo}, this is the
 * Open Type of the attribute or parameter.  In the case of {@code
 * MBeanOperationInfo}, it is the Open Type of the return value.  This
 * field is set in the Descriptor for all instances of {@link
 * OpenMBeanAttributeInfoSupport}, {@link
 * OpenMBeanOperationInfoSupport}, and {@link
 * OpenMBeanParameterInfoSupport}.  It is also set for attributes,
 * operations, and parameters of MXBeans.</p>
 *
 * <p>This field can be set for an {@code MBeanNotificationInfo}, in
 * which case it indicates the Open Type that the {@link
 * Notification#getUserData() user data} will have.</td>
 *
 * <tr id="originalType"><th scope="row"><i>originalType</i><td>String</td>
 * <td>MBeanAttributeInfo<br>MBeanOperationInfo<br>MBeanParameterInfo</td>
 *
 * <td><p>The original Java type of this element as it appeared in the
 * {@link MXBean} interface method that produced this {@code
 * MBeanAttributeInfo} (etc).  For example, a method<br> <code>public
 * </code> {@link MemoryUsage}<code> getHeapMemoryUsage();</code><br>
 * in an MXBean interface defines an attribute called {@code
 * HeapMemoryUsage} of type {@link CompositeData}.  The {@code
 * originalType} field in the Descriptor for this attribute will have
 * the value {@code "java.lang.management.MemoryUsage"}.
 *
 * <p>The format of this string is described in the section <a
 * href="MXBean.html#type-names">Type Names</a> of the MXBean
 * specification.</p>
 *
 * <tr id="setExceptions"><th scope="row"><i>setExceptions</i><td>String[]</td>
 * <td>MBeanAttributeInfo</td>
 *
 * <td>The class names of the exceptions that can be thrown when setting
 * an attribute. The meaning of this field
 * is defined by this specification but the field is not set or used by the
 * JMX API itself.  Exceptions thrown when getting an attribute are specified
 * by the field <a href="#exceptions">{@code exceptions}</a>.
 *
 * <tr><th scope="row">severity</th><td>String<br>Integer</td>
 * <td>MBeanNotificationInfo</td>
 *
 * <td>The severity of this notification.  It can be 0 to mean
 * unknown severity or a value from 1 to 6 representing decreasing
 * levels of severity.  It can be represented as a decimal string or
 * an {@code Integer}.</td>
 *
 * <tr><th scope="row">since</th><td>String</td><td>Any</td>
 *
 * <td>The version of the information model in which this element
 * was introduced.  A set of MBeans defined by an application is
 * collectively called an <em>information model</em>.  The
 * application may also define versions of this model, and use the
 * {@code "since"} field to record the version in which an element
 * first appeared.</td>
 *
 * <tr><th scope="row">units</th><td>String</td>
 * <td>MBeanAttributeInfo<br>MBeanParameterInfo<br>MBeanOperationInfo</td>
 *
 * <td>The units in which an attribute, parameter, or operation return
 * value is measured, for example {@code "bytes"} or {@code
 * "seconds"}.</td>
 *
 * </tbody>
 * </table>
 *
 * <p>Some additional fields are defined by Model MBeans.  See the
 * information for <a href="modelmbean/ModelMBeanInfo.html#descriptor"><!--
 * -->{@code ModelMBeanInfo}</a>,
 * <a href="modelmbean/ModelMBeanAttributeInfo.html#descriptor"><!--
 * -->{@code ModelMBeanAttributeInfo}</a>,
 * <a href="modelmbean/ModelMBeanConstructorInfo.html#descriptor"><!--
 * -->{@code ModelMBeanConstructorInfo}</a>,
 * <a href="modelmbean/ModelMBeanNotificationInfo.html#descriptor"><!--
 * -->{@code ModelMBeanNotificationInfo}</a>, and
 * <a href="modelmbean/ModelMBeanOperationInfo.html#descriptor"><!--
 * -->{@code ModelMBeanOperationInfo}</a>, as
 * well as the chapter "Model MBeans" of the <a
 * href="http://www.oracle.com/technetwork/java/javase/tech/javamanagement-140525.html">JMX
 * Specification</a>.  The following table summarizes these fields.  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>
 *
 * <p>Nothing prevents the use of these fields in MBeans that are not Model
 * MBeans.  The <a href="#displayName">displayName</a>, <a href="#severity"><!--
 * -->severity</a>, and <a href="#visibility">visibility</a> fields are of
 * interest outside Model MBeans, for example.  But only Model MBeans have
 * a predefined behavior for these fields.</p>
 *
 * <table class="striped">
 * <caption style="display:none">ModelMBean Fields</caption>
 *
 * <thead>
 * <tr><th scope="col">Name</th>
 *     <th scope="col">Type</th>
 *     <th scope="col">Used in</th>
 *     <th scope="col">Meaning</th></tr>
 * </thead>
 *
 * <tbody style="text-align:left">
 * <tr><th scope="row">class</th><td>String</td><td>ModelMBeanOperationInfo</td>
 *     <td>Class where method is defined (fully qualified).</td></tr>
 *
 * <tr><th scope="row">currencyTimeLimit</th><td>Number</td>
 *     <td>ModelMBeanInfo<br>ModelMBeanAttributeInfo<br>ModelMBeanOperationInfo</td>
 *     <td>How long cached value is valid: &lt;0 never, =0 always,
 *         &gt;0 seconds.</td></tr>
 *
 * <tr><th scope="row">default</th><td>Object</td><td>ModelMBeanAttributeInfo</td>
 *     <td>Default value for attribute.</td></tr>
 *
 * <tr><th scope="row">descriptorType</th><td>String</td><td>Any</td>
 *     <td>Type of descriptor, "mbean", "attribute", "constructor", "operation",
 *         or "notification".</td></tr>
 *
 * <tr id="displayName"><th scope="row">displayName</th><td>String</td><td>Any</td>
 *     <td>Human readable name of this item.</td></tr>
 *
 * <tr><th scope="row">export</th><td>String</td><td>ModelMBeanInfo</td>
 *     <td>Name to be used to export/expose this MBean so that it is
 *         findable by other JMX Agents.</td></tr>
 *
 * <tr><th scope="row">getMethod</th><td>String</td><td>ModelMBeanAttributeInfo</td>
 *     <td>Name of operation descriptor for get method.</td></tr>
 *
 * <tr><th scope="row">lastUpdatedTimeStamp</th><td>Number</td>
 *     <td>ModelMBeanAttributeInfo<br>ModelMBeanOperationInfo</td>
 *     <td>When <a href="#value-field">value</a> was set.</td></tr>
 *
 * <tr><th scope="row">log</th><td>String</td><td>ModelMBeanInfo<br>ModelMBeanNotificationInfo</td>
 *     <td>t or T: log all notifications, f or F: log no notifications.</td></tr>
 *
 * <tr><th scope="row">logFile</th><td>String</td><td>ModelMBeanInfo<br>ModelMBeanNotificationInfo</td>
 *     <td>Fully qualified filename to log events to.</td></tr>
 *
 * <tr><th scope="row">messageID</th><td>String</td><td>ModelMBeanNotificationInfo</td>
 *     <td>Unique key for message text (to allow translation, analysis).</td></tr>
 *
 * <tr><th scope="row">messageText</th><td>String</td><td>ModelMBeanNotificationInfo</td>
 *     <td>Text of notification.</td></tr>
 *
 * <tr><th scope="row">name</th><td>String</td><td>Any</td>
 *     <td>Name of this item.</td></tr>
 *
 * <tr><th scope="row">persistFile</th><td>String</td><td>ModelMBeanInfo</td>
 *     <td>File name into which the MBean should be persisted.</td></tr>
 *
 * <tr><th scope="row">persistLocation</th><td>String</td><td>ModelMBeanInfo</td>
 *     <td>The fully qualified directory name where the MBean should be
 *         persisted (if appropriate).</td></tr>
 *
 * <tr><th scope="row">persistPeriod</th><td>Number</td>
 *     <td>ModelMBeanInfo<br>ModelMBeanAttributeInfo</td>
 *     <td>Frequency of persist cycle in seconds. Used when persistPolicy is
 *         "OnTimer" or "NoMoreOftenThan".</td></tr>
 *
 * <tr><th scope="row">persistPolicy</th><td>String</td>
 *     <td>ModelMBeanInfo<br>ModelMBeanAttributeInfo</td>
 *     <td>One of: OnUpdate|OnTimer|NoMoreOftenThan|OnUnregister|Always|Never.
 *         See the section "MBean Descriptor Fields" in the JMX specification
 *         document.</td></tr>
 *
 * <tr><th scope="row">presentationString</th><td>String</td><td>Any</td>
 *     <td>XML formatted string to allow presentation of data.</td></tr>
 *
 * <tr><th scope="row">protocolMap</th><td>Descriptor</td><td>ModelMBeanAttributeInfo</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><th scope="row">role</th><td>String</td>
 *     <td>ModelMBeanConstructorInfo<br>ModelMBeanOperationInfo</td>
 *     <td>One of "constructor", "operation", "getter", or "setter".</td></tr>
 *
 * <tr><th scope="row">setMethod</th><td>String</td><td>ModelMBeanAttributeInfo</td>
 *     <td>Name of operation descriptor for set method.</td></tr>
 *
 * <tr id="severity"><th scope="row">severity</th><td>Number</td>
 *     <td>ModelMBeanNotificationInfo</td>
 *     <td>0-6 where 0: unknown; 1: non-recoverable;
 *         2: critical, failure; 3: major, severe;
 *         4: minor, marginal, error; 5: warning;
 *         6: normal, cleared, informative</td></tr>
 *
 * <tr><th scope="row">targetObject</th><td>Object</td><td>ModelMBeanOperationInfo</td>
 *     <td>Object on which to execute this method.</td></tr>
 *
 * <tr><th scope="row">targetType</th><td>String</td><td>ModelMBeanOperationInfo</td>
 *     <td>type of object reference for targetObject. Can be:
 *         ObjectReference | Handle | EJBHandle | IOR | RMIReference.</td></tr>
 *
 * <tr id="value-field"><th scope="row">value</th><td>Object</td>
 *     <td>ModelMBeanAttributeInfo<br>ModelMBeanOperationInfo</td>
 *     <td>Current (cached) value for attribute or operation.</td></tr>
 *
 * <tr id="visibility"><th scope="row">visibility</th><td>Number</td><td>Any</td>
 *     <td>1-4 where 1: always visible, 4: rarely visible.</td></tr>
 *
 * </tbody>
 * </table>
 *
 * @since 1.5
 */
public interface Descriptor extends Serializable, Cloneable
{

    
Returns the value for a specific field name, or null if no value
is present for that name.

Params:
  • fieldName – the field name.
Throws:
Returns:the corresponding value, or null if the field is not present.
/**
     * Returns the value for a specific field name, or null if no value
     * is present for that name.
     *
     * @param fieldName the field name.
     *
     * @return the corresponding value, or null if the field is not present.
     *
     * @exception RuntimeOperationsException if the field name is illegal.
     */
    public Object getFieldValue(String fieldName)
            throws RuntimeOperationsException;

    
Sets the value for a specific field name. This will
modify an existing field or add a new field.


The field value will be validated before it is set.
If it is not valid, then an exception will be thrown.
The meaning of validity is dependent on the descriptor
implementation.


Params:
  • fieldName – The field name to be set. Cannot be null or empty.
  • fieldValue – The field value to be set for the field
name. Can be null if that is a valid value for the field.
Throws:
/**
     * <p>Sets the value for a specific field name. This will
     * modify an existing field or add a new field.</p>
     *
     * <p>The field value will be validated before it is set.
     * If it is not valid, then an exception will be thrown.
     * The meaning of validity is dependent on the descriptor
     * implementation.</p>
     *
     * @param fieldName The field name to be set. Cannot be null or empty.
     * @param fieldValue The field value to be set for the field
     * name. Can be null if that is a valid value for the field.
     *
     * @exception RuntimeOperationsException if the field name or field value
     * is illegal (wrapped exception is {@link IllegalArgumentException}); or
     * if the descriptor is immutable (wrapped exception is
     * {@link UnsupportedOperationException}).
     */
    public void setField(String fieldName, Object fieldValue)
        throws RuntimeOperationsException;


    
Returns all of the fields contained in this descriptor as a string array.

See Also:
Returns:String array of fields in the format fieldName=fieldValue

If the value of a field is not a String, then the toString() method
will be called on it and the returned value, enclosed in parentheses,
used as the value for the field in the returned array. If the value
of a field is null, then the value of the field in the returned array
will be empty.  If the descriptor is empty, you will get
an empty array.
/**
     * Returns all of the fields contained in this descriptor as a string array.
     *
     * @return String array of fields in the format <i>fieldName=fieldValue</i>
     * <br>If the value of a field is not a String, then the toString() method
     * will be called on it and the returned value, enclosed in parentheses,
     * used as the value for the field in the returned array. If the value
     * of a field is null, then the value of the field in the returned array
     * will be empty.  If the descriptor is empty, you will get
     * an empty array.
     *
     * @see #setFields
     */
    public String[] getFields();


    
Returns all the field names in the descriptor.

Returns:String array of field names. If the descriptor is empty,
you will get an empty array.
/**
     * Returns all the field names in the descriptor.
     *
     * @return String array of field names. If the descriptor is empty,
     * you will get an empty array.
     */
    public String[] getFieldNames();

    
Returns all the field values in the descriptor as an array of Objects. The returned values are in the same order as the fieldNames String array parameter. 
Params:
  • fieldNames – String array of the names of the fields that the values should be returned for. If the array is empty then an empty array will be returned. If the array is null then all values will be returned, as if the parameter were the array returned by getFieldNames(). If a field name in the array does not exist, including the case where it is null or the empty string, then null is returned for the matching array element being returned.
Returns:Object array of field values. If the list of fieldNames is empty, you will get an empty array.
/**
     * Returns all the field values in the descriptor as an array of Objects. The
     * returned values are in the same order as the {@code fieldNames} String array parameter.
     *
     * @param fieldNames String array of the names of the fields that
     * the values should be returned for.  If the array is empty then
     * an empty array will be returned.  If the array is null then all
     * values will be returned, as if the parameter were the array
     * returned by {@link #getFieldNames()}.  If a field name in the
     * array does not exist, including the case where it is null or
     * the empty string, then null is returned for the matching array
     * element being returned.
     *
     * @return Object array of field values. If the list of {@code fieldNames}
     * is empty, you will get an empty array.
     */
    public Object[] getFieldValues(String... fieldNames);

    
Removes a field from the descriptor.

Params:
  • fieldName – String name of the field to be removed.
If the field name is illegal or the field is not found,
no exception is thrown.
Throws:
/**
     * Removes a field from the descriptor.
     *
     * @param fieldName String name of the field to be removed.
     * If the field name is illegal or the field is not found,
     * no exception is thrown.
     *
     * @exception RuntimeOperationsException if a field of the given name
     * exists and the descriptor is immutable.  The wrapped exception will
     * be an {@link UnsupportedOperationException}.
     */
    public void removeField(String fieldName);

    
Sets all fields in the field names array to the new value with
the same index in the field values array. Array sizes must match.


The field value will be validated before it is set.
If it is not valid, then an exception will be thrown.
If the arrays are empty, then no change will take effect.


Params:
  • fieldNames – String array of field names. The array and array
elements cannot be null.
  • fieldValues – Object array of the corresponding field values.
The array cannot be null. Elements of the array can be null.
Throws:
See Also:
/**
     * <p>Sets all fields in the field names array to the new value with
     * the same index in the field values array. Array sizes must match.</p>
     *
     * <p>The field value will be validated before it is set.
     * If it is not valid, then an exception will be thrown.
     * If the arrays are empty, then no change will take effect.</p>
     *
     * @param fieldNames String array of field names. The array and array
     * elements cannot be null.
     * @param fieldValues Object array of the corresponding field values.
     * The array cannot be null. Elements of the array can be null.
     *
     * @throws RuntimeOperationsException if the change fails for any reason.
     * Wrapped exception is {@link IllegalArgumentException} if
     * {@code fieldNames} or {@code fieldValues} is null, or if
     * the arrays are of different lengths, or if there is an
     * illegal value in one of them.
     * Wrapped exception is {@link UnsupportedOperationException}
     * if the descriptor is immutable, and the call would change
     * its contents.
     *
     * @see #getFields
     */
    public void setFields(String[] fieldNames, Object[] fieldValues)
        throws RuntimeOperationsException;


    
Returns a descriptor which is equal to this descriptor.
Changes to the returned descriptor will have no effect on this
descriptor, and vice versa.  If this descriptor is immutable,
it may fulfill this condition by returning itself.


Throws:
  • RuntimeOperationsException – for illegal value for field names
or field values.
If the descriptor construction fails for any reason, this exception will
be thrown.
Returns:A descriptor which is equal to this descriptor.
/**
     * <p>Returns a descriptor which is equal to this descriptor.
     * Changes to the returned descriptor will have no effect on this
     * descriptor, and vice versa.  If this descriptor is immutable,
     * it may fulfill this condition by returning itself.</p>
     * @exception RuntimeOperationsException for illegal value for field names
     * or field values.
     * If the descriptor construction fails for any reason, this exception will
     * be thrown.
     * @return A descriptor which is equal to this descriptor.
     */
    public Object clone() throws RuntimeOperationsException;


    
Returns true if all of the fields have legal values given their
names.

Throws:
  • RuntimeOperationsException – If the validity checking fails for
any reason, this exception will be thrown.
The method returns false if the descriptor is not valid, but throws
this exception if the attempt to determine validity fails.
Returns:true if the values are legal.
/**
     * Returns true if all of the fields have legal values given their
     * names.
     *
     * @return true if the values are legal.
     *
     * @exception RuntimeOperationsException If the validity checking fails for
     * any reason, this exception will be thrown.
     * The method returns false if the descriptor is not valid, but throws
     * this exception if the attempt to determine validity fails.
     */
    public boolean isValid() throws RuntimeOperationsException;

    
Compares this descriptor to the given object.  The objects are equal if
the given object is also a Descriptor, and if the two Descriptors have
the same field names (possibly differing in case) and the same
associated values.  The respective values for a field in the two
Descriptors are equal if the following conditions hold:


    

  • If one value is null then the other must be too.
    • 

  • If one value is a primitive array then the other must be a primitive
array of the same type with the same elements.
    • 

  • If one value is an object array then the other must be too and Arrays.deepEquals(Object[], Object[]) must return true.
    • 

  • Otherwise Object.equals(Object) must return true.
    • 



Params:
  • obj – the object to compare with.
Returns:true if the objects are the same; false otherwise.
Since:1.6
/**
     * <p>Compares this descriptor to the given object.  The objects are equal if
     * the given object is also a Descriptor, and if the two Descriptors have
     * the same field names (possibly differing in case) and the same
     * associated values.  The respective values for a field in the two
     * Descriptors are equal if the following conditions hold:</p>
     *
     * <ul>
     * <li>If one value is null then the other must be too.</li>
     * <li>If one value is a primitive array then the other must be a primitive
     * array of the same type with the same elements.</li>
     * <li>If one value is an object array then the other must be too and
     * {@link Arrays#deepEquals(Object[],Object[])} must return true.</li>
     * <li>Otherwise {@link Object#equals(Object)} must return true.</li>
     * </ul>
     *
     * @param obj the object to compare with.
     *
     * @return {@code true} if the objects are the same; {@code false}
     * otherwise.
     *
     * @since 1.6
     */
    public boolean equals(Object obj);

    
Returns the hash code value for this descriptor. The hash code is computed as the sum of the hash codes for each field in the descriptor. The hash code of a field with name n and value v is n.toLowerCase().hashCode() ^ h. Here h is the hash code of v, computed as follows:


    

  • If v is null then h is 0.
    • 

  • If v is a primitive array then h is computed using the appropriate overloading of java.util.Arrays.hashCode.
    • 

  • If v is an object array then h is computed using Arrays.deepHashCode(Object[]).
    • 

  • Otherwise h is v.hashCode().
    • 



Returns:A hash code value for this object.
Since:1.6
/**
     * <p>Returns the hash code value for this descriptor.  The hash
     * code is computed as the sum of the hash codes for each field in
     * the descriptor.  The hash code of a field with name {@code n}
     * and value {@code v} is {@code n.toLowerCase().hashCode() ^ h}.
     * Here {@code h} is the hash code of {@code v}, computed as
     * follows:</p>
     *
     * <ul>
     * <li>If {@code v} is null then {@code h} is 0.</li>
     * <li>If {@code v} is a primitive array then {@code h} is computed using
     * the appropriate overloading of {@code java.util.Arrays.hashCode}.</li>
     * <li>If {@code v} is an object array then {@code h} is computed using
     * {@link Arrays#deepHashCode(Object[])}.</li>
     * <li>Otherwise {@code h} is {@code v.hashCode()}.</li>
     * </ul>
     *
     * @return A hash code value for this object.
     *
     * @since 1.6
     */
    public int hashCode();
}