/*
 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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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;

/**
 * <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 border="1" cellpadding="5" summary="Descriptor Fields">
 *
 * <tr><th>Name</th><th>Type</th><th>Used in</th><th>Meaning</th></tr>
 *
 * <tr id="defaultValue"><td><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><td>deprecated</td><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><td id="descriptionResourceBundleBaseName">descriptionResource<br>
 * BundleBaseName</td><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><td id="descriptionResourceKey">descriptionResourceKey</td>
 * <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><td>enabled</td><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"><td>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"><td><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"><td>infoTimeout</td><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"><td><i>interfaceClassName</i></td>
 * <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"><td><i>legalValues</i></td>
 * <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"><td>locale</td>
 * <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"><td><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"><td>metricType</td><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"><td><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"><td><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"><td><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"><td><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"><td><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><td>severity</td><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><td>since</td><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><td>units</td><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>
 *
 * </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 border="1" cellpadding="5" summary="ModelMBean Fields">
 *
 * <tr><th>Name</th><th>Type</th><th>Used in</th><th>Meaning</th></tr>
 *
 * <tr><td>class</td><td>String</td><td>ModelMBeanOperationInfo</td>
 * <td>Class where method is defined (fully qualified).</td></tr>
 *
 * <tr><td>currencyTimeLimit</td><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><td>default</td><td>Object</td><td>ModelMBeanAttributeInfo</td>
 * <td>Default value for attribute.</td></tr>
 *
 * <tr><td>descriptorType</td><td>String</td><td>Any</td>
 * <td>Type of descriptor, "mbean", "attribute", "constructor", "operation",
 * or "notification".</td></tr>
 *
 * <tr id="displayName"><td>displayName</td><td>String</td><td>Any</td>
 * <td>Human readable name of this item.</td></tr>
 *
 * <tr><td>export</td><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><td>getMethod</td><td>String</td><td>ModelMBeanAttributeInfo</td>
 * <td>Name of operation descriptor for get method.</td></tr>
 *
 * <tr><td>lastUpdatedTimeStamp</td><td>Number</td>
 * <td>ModelMBeanAttributeInfo<br>ModelMBeanOperationInfo</td>
 * <td>When <a href="#value-field">value</a> was set.</td></tr>
 *
 * <tr><td>log</td><td>String</td><td>ModelMBeanInfo<br>ModelMBeanNotificationInfo</td>
 * <td>t or T: log all notifications, f or F: log no notifications.</td></tr>
 *
 * <tr><td>logFile</td><td>String</td><td>ModelMBeanInfo<br>ModelMBeanNotificationInfo</td>
 * <td>Fully qualified filename to log events to.</td></tr>
 *
 * <tr><td>messageID</td><td>String</td><td>ModelMBeanNotificationInfo</td>
 * <td>Unique key for message text (to allow translation, analysis).</td></tr>
 *
 * <tr><td>messageText</td><td>String</td><td>ModelMBeanNotificationInfo</td>
 * <td>Text of notification.</td></tr>
 *
 * <tr><td>name</td><td>String</td><td>Any</td>
 * <td>Name of this item.</td></tr>
 *
 * <tr><td>persistFile</td><td>String</td><td>ModelMBeanInfo</td>
 * <td>File name into which the MBean should be persisted.</td></tr>
 *
 * <tr><td>persistLocation</td><td>String</td><td>ModelMBeanInfo</td>
 * <td>The fully qualified directory name where the MBean should be
 * persisted (if appropriate).</td></tr>
 *
 * <tr><td>persistPeriod</td><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><td>persistPolicy</td><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><td>presentationString</td><td>String</td><td>Any</td>
 * <td>XML formatted string to allow presentation of data.</td></tr>
 *
 * <tr><td>protocolMap</td><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><td>role</td><td>String</td>
 * <td>ModelMBeanConstructorInfo<br>ModelMBeanOperationInfo</td>
 * <td>One of "constructor", "operation", "getter", or "setter".</td></tr>
 *
 * <tr><td>setMethod</td><td>String</td><td>ModelMBeanAttributeInfo</td>
 * <td>Name of operation descriptor for set method.</td></tr>
 *
 * <tr id="severity"><td>severity</td><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><td>targetObject</td><td>Object</td><td>ModelMBeanOperationInfo</td>
 * <td>Object on which to execute this method.</td></tr>
 *
 * <tr><td>targetType</td><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"><td>value</td><td>Object</td>
 * <td>ModelMBeanAttributeInfo<br>ModelMBeanOperationInfo</td>
 * <td>Current (cached) value for attribute or operation.</td></tr>
 *
 * <tr id="visibility"><td>visibility</td><td>Number</td><td>Any</td>
 * <td>1-4 where 1: always visible, 4: rarely visible.</td></tr>
 *
 * </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.
 *
 * @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;

 /**
 * <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.
 *
 * @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.
 *
 * @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 {@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.
 *
 * @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);

 /**
 * <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;


 /**
 * <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.
 *
 * @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;

 /**
 * <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);

 /**
 * <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();
}