OpenMBeanAttributeInfoSupport.java

/*
 * Copyright (c) 2000, 2021, 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.
 */


package javax.management.openmbean;


import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import javax.management.Descriptor;
import javax.management.DescriptorRead;
import javax.management.ImmutableDescriptor;
import javax.management.MBeanAttributeInfo;
import sun.reflect.misc.MethodUtil;
import sun.reflect.misc.ReflectUtil;

/**
 * Describes an attribute of an open MBean.
 *
 *
 * @since 1.5
 */
public class OpenMBeanAttributeInfoSupport
    extends MBeanAttributeInfo
    implements OpenMBeanAttributeInfo {

    /* Serial version */
    static final long serialVersionUID = -4867215622149721849L;

    /**
     * @serial The open mbean attribute's <i>open type</i>
     */
    @SuppressWarnings("serial") // Not statically typed as Serializable
    private OpenType<?> openType;

    /**
     * @serial The open mbean attribute's default value
     */
    @SuppressWarnings("serial") // Not statically typed as Serializable
    private final Object defaultValue;

    /**
     * @serial The open mbean attribute's legal values. This {@link
     * Set} is unmodifiable
     */
    @SuppressWarnings("serial") // Conditionally serializable
    private final Set<?> legalValues;  // to be constructed unmodifiable

    /**
     * @serial The open mbean attribute's min value
     */
    @SuppressWarnings("serial") // Conditionally serializable
    private final Comparable<?> minValue;

    /**
     * @serial The open mbean attribute's max value
     */
    @SuppressWarnings("serial") // Conditionally serializable
    private final Comparable<?> maxValue;


    // As this instance is immutable, these two values need only
    // be calculated once.
    private transient Integer myHashCode = null;
    private transient String  myToString = null;


    /**
     * Constructs an {@code OpenMBeanAttributeInfoSupport} instance,
     * which describes the attribute of an open MBean with the
     * specified {@code name}, {@code openType} and {@code
     * description}, and the specified read/write access properties.
     *
     * @param name  cannot be a null or empty string.
     *
     * @param description  cannot be a null or empty string.
     *
     * @param openType  cannot be null.
     *
     * @param isReadable {@code true} if the attribute has a getter
     * exposed for management.
     *
     * @param isWritable {@code true} if the attribute has a setter
     * exposed for management.
     *
     * @param isIs {@code true} if the attribute's getter is of the
     * form <code>is<i>XXX</i></code>.
     *
     * @throws IllegalArgumentException if {@code name} or {@code
     * description} are null or empty string, or {@code openType} is
     * null.
     */
    public OpenMBeanAttributeInfoSupport(String name,
                                         String description,
                                         OpenType<?> openType,
                                         boolean isReadable,
                                         boolean isWritable,
                                         boolean isIs) {
        this(name, description, openType, isReadable, isWritable, isIs,
             (Descriptor) null);
    }

    /**
     * <p>Constructs an {@code OpenMBeanAttributeInfoSupport} instance,
     * which describes the attribute of an open MBean with the
     * specified {@code name}, {@code openType}, {@code
     * description}, read/write access properties, and {@code Descriptor}.</p>
     *
     * <p>The {@code descriptor} can contain entries that will define
     * the values returned by certain methods of this class, as
     * explained in the <a href="package-summary.html#constraints">
     * package description</a>.
     *
     * @param name  cannot be a null or empty string.
     *
     * @param description  cannot be a null or empty string.
     *
     * @param openType  cannot be null.
     *
     * @param isReadable {@code true} if the attribute has a getter
     * exposed for management.
     *
     * @param isWritable {@code true} if the attribute has a setter
     * exposed for management.
     *
     * @param isIs {@code true} if the attribute's getter is of the
     * form <code>is<i>XXX</i></code>.
     *
     * @param descriptor The descriptor for the attribute.  This may be null
     * which is equivalent to an empty descriptor.
     *
     * @throws IllegalArgumentException if {@code name} or {@code
     * description} are null or empty string, or {@code openType} is
     * null, or the descriptor entries are invalid as described in the
     * <a href="package-summary.html#constraints">package description</a>.
     *
     * @since 1.6
     */
    public OpenMBeanAttributeInfoSupport(String name,
                                         String description,
                                         OpenType<?> openType,
                                         boolean isReadable,
                                         boolean isWritable,
                                         boolean isIs,
                                         Descriptor descriptor) {
        // Construct parent's state
        //
        super(name,
              (openType==null) ? null : openType.getClassName(),
              description,
              isReadable,
              isWritable,
              isIs,
              ImmutableDescriptor.union(descriptor, (openType==null)?null:
                openType.getDescriptor()));

        // Initialize this instance's specific state
        //
        this.openType = openType;

        descriptor = getDescriptor();  // replace null by empty
        this.defaultValue = valueFrom(descriptor, "defaultValue", openType);
        this.legalValues = valuesFrom(descriptor, "legalValues", openType);
        this.minValue = comparableValueFrom(descriptor, "minValue", openType);
        this.maxValue = comparableValueFrom(descriptor, "maxValue", openType);

        try {
            check(this);
        } catch (OpenDataException e) {
            throw new IllegalArgumentException(e.getMessage(), e);
        }
    }

    /**
     * Constructs an {@code OpenMBeanAttributeInfoSupport} instance,
     * which describes the attribute of an open MBean with the
     * specified {@code name}, {@code openType}, {@code description}
     * and {@code defaultValue}, and the specified read/write access
     * properties.
     *
     * @param name  cannot be a null or empty string.
     *
     * @param description  cannot be a null or empty string.
     *
     * @param openType  cannot be null.
     *
     * @param isReadable {@code true} if the attribute has a getter
     * exposed for management.
     *
     * @param isWritable {@code true} if the attribute has a setter
     * exposed for management.
     *
     * @param isIs {@code true} if the attribute's getter is of the
     * form <code>is<i>XXX</i></code>.
     *
     * @param defaultValue must be a valid value for the {@code
     * openType} specified for this attribute; default value not
     * supported for {@code ArrayType} and {@code TabularType}; can
     * be null, in which case it means that no default value is set.
     *
     * @param <T> allows the compiler to check that the {@code defaultValue},
     * if non-null, has the correct Java type for the given {@code openType}.
     *
     * @throws IllegalArgumentException if {@code name} or {@code
     * description} are null or empty string, or {@code openType} is
     * null.
     *
     * @throws OpenDataException if {@code defaultValue} is not a
     * valid value for the specified {@code openType}, or {@code
     * defaultValue} is non null and {@code openType} is an {@code
     * ArrayType} or a {@code TabularType}.
     */
    public <T> OpenMBeanAttributeInfoSupport(String   name,
                                             String   description,
                                             OpenType<T> openType,
                                             boolean  isReadable,
                                             boolean  isWritable,
                                             boolean  isIs,
                                             T        defaultValue)
            throws OpenDataException {
        this(name, description, openType, isReadable, isWritable, isIs,
             defaultValue, (T[]) null);
    }


    /**
     * <p>Constructs an {@code OpenMBeanAttributeInfoSupport} instance,
     * which describes the attribute of an open MBean with the
     * specified {@code name}, {@code openType}, {@code description},
     * {@code defaultValue} and {@code legalValues}, and the specified
     * read/write access properties.</p>
     *
     * <p>The contents of {@code legalValues} are copied, so subsequent
     * modifications of the array referenced by {@code legalValues}
     * have no impact on this {@code OpenMBeanAttributeInfoSupport}
     * instance.</p>
     *
     * @param name  cannot be a null or empty string.
     *
     * @param description  cannot be a null or empty string.
     *
     * @param openType  cannot be null.
     *
     * @param isReadable {@code true} if the attribute has a getter
     * exposed for management.
     *
     * @param isWritable {@code true} if the attribute has a setter
     * exposed for management.
     *
     * @param isIs {@code true} if the attribute's getter is of the
     * form <code>is<i>XXX</i></code>.
     *
     * @param defaultValue must be a valid value
     * for the {@code
     * openType} specified for this attribute; default value not
     * supported for {@code ArrayType} and {@code TabularType}; can
     * be null, in which case it means that no default value is set.
     *
     * @param legalValues each contained value must be valid for the
     * {@code openType} specified for this attribute; legal values
     * not supported for {@code ArrayType} and {@code TabularType};
     * can be null or empty.
     *
     * @param <T> allows the compiler to check that the {@code
     * defaultValue} and {@code legalValues}, if non-null, have the
     * correct Java type for the given {@code openType}.
     *
     * @throws IllegalArgumentException if {@code name} or {@code
     * description} are null or empty string, or {@code openType} is
     * null.
     *
     * @throws OpenDataException if {@code defaultValue} is not a
     * valid value for the specified {@code openType}, or one value in
     * {@code legalValues} is not valid for the specified {@code
     * openType}, or {@code defaultValue} is non null and {@code
     * openType} is an {@code ArrayType} or a {@code TabularType}, or
     * {@code legalValues} is non null and non empty and {@code
     * openType} is an {@code ArrayType} or a {@code TabularType}, or
     * {@code legalValues} is non null and non empty and {@code
     * defaultValue} is not contained in {@code legalValues}.
     */
    public <T> OpenMBeanAttributeInfoSupport(String   name,
                                             String   description,
                                             OpenType<T> openType,
                                             boolean  isReadable,
                                             boolean  isWritable,
                                             boolean  isIs,
                                             T        defaultValue,
                                             T[]      legalValues)
            throws OpenDataException {
        this(name, description, openType, isReadable, isWritable, isIs,
             defaultValue, legalValues, null, null);
    }


    /**
     * Constructs an {@code OpenMBeanAttributeInfoSupport} instance,
     * which describes the attribute of an open MBean, with the
     * specified {@code name}, {@code openType}, {@code description},
     * {@code defaultValue}, {@code minValue} and {@code maxValue}.
     *
     * It is possible to specify minimal and maximal values only for
     * an open type whose values are {@code Comparable}.
     *
     * @param name  cannot be a null or empty string.
     *
     * @param description  cannot be a null or empty string.
     *
     * @param openType  cannot be null.
     *
     * @param isReadable {@code true} if the attribute has a getter
     * exposed for management.
     *
     * @param isWritable {@code true} if the attribute has a setter
     * exposed for management.
     *
     * @param isIs {@code true} if the attribute's getter is of the
     * form <code>is<i>XXX</i></code>.
     *
     * @param defaultValue must be a valid value for the {@code
     * openType} specified for this attribute; default value not
     * supported for {@code ArrayType} and {@code TabularType}; can be
     * null, in which case it means that no default value is set.
     *
     * @param minValue must be valid for the {@code openType}
     * specified for this attribute; can be null, in which case it
     * means that no minimal value is set.
     *
     * @param maxValue must be valid for the {@code openType}
     * specified for this attribute; can be null, in which case it
     * means that no maximal value is set.
     *
     * @param <T> allows the compiler to check that the {@code
     * defaultValue}, {@code minValue}, and {@code maxValue}, if
     * non-null, have the correct Java type for the given {@code
     * openType}.
     *
     * @throws IllegalArgumentException if {@code name} or {@code
     * description} are null or empty string, or {@code openType} is
     * null.
     *
     * @throws OpenDataException if {@code defaultValue}, {@code
     * minValue} or {@code maxValue} is not a valid value for the
     * specified {@code openType}, or {@code defaultValue} is non null
     * and {@code openType} is an {@code ArrayType} or a {@code
     * TabularType}, or both {@code minValue} and {@code maxValue} are
     * non-null and {@code minValue.compareTo(maxValue) > 0} is {@code
     * true}, or both {@code defaultValue} and {@code minValue} are
     * non-null and {@code minValue.compareTo(defaultValue) > 0} is
     * {@code true}, or both {@code defaultValue} and {@code maxValue}
     * are non-null and {@code defaultValue.compareTo(maxValue) > 0}
     * is {@code true}.
     */
    public <T> OpenMBeanAttributeInfoSupport(String     name,
                                             String     description,
                                             OpenType<T>   openType,
                                             boolean    isReadable,
                                             boolean    isWritable,
                                             boolean    isIs,
                                             T          defaultValue,
                                             Comparable<T> minValue,
                                             Comparable<T> maxValue)
            throws OpenDataException {
        this(name, description, openType, isReadable, isWritable, isIs,
             defaultValue, null, minValue, maxValue);
    }

    private <T> OpenMBeanAttributeInfoSupport(String name,
                                              String description,
                                              OpenType<T> openType,
                                              boolean isReadable,
                                              boolean isWritable,
                                              boolean isIs,
                                              T defaultValue,
                                              T[] legalValues,
                                              Comparable<T> minValue,
                                              Comparable<T> maxValue)
            throws OpenDataException {
        super(name,
              (openType==null) ? null : openType.getClassName(),
              description,
              isReadable,
              isWritable,
              isIs,
              makeDescriptor(openType,
                             defaultValue, legalValues, minValue, maxValue));

        this.openType = openType;

        Descriptor d = getDescriptor();
        this.defaultValue = defaultValue;
        this.minValue = minValue;
        this.maxValue = maxValue;
        // We already converted the array into an unmodifiable Set
        // in the descriptor.
        this.legalValues = (Set<?>) d.getFieldValue("legalValues");

        check(this);
    }

    /**
     * An object serialized in a version of the API before Descriptors were
     * added to this class will have an empty or null Descriptor.
     * For consistency with our
     * behavior in this version, we must replace the object with one
     * where the Descriptors reflect the same values of openType, defaultValue,
     * etc.
     **/
    private Object readResolve() {
        if (getDescriptor().getFieldNames().length == 0) {
            OpenType<Object> xopenType = cast(openType);
            Set<Object> xlegalValues = cast(legalValues);
            Comparable<Object> xminValue = cast(minValue);
            Comparable<Object> xmaxValue = cast(maxValue);
            return new OpenMBeanAttributeInfoSupport(
                    name, description, openType,
                    isReadable(), isWritable(), isIs(),
                    makeDescriptor(xopenType, defaultValue, xlegalValues,
                                   xminValue, xmaxValue));
        } else
            return this;
    }

    static void check(OpenMBeanParameterInfo info) throws OpenDataException {
        OpenType<?> openType = info.getOpenType();
        if (openType == null)
            throw new IllegalArgumentException("OpenType cannot be null");

        if (info.getName() == null ||
                info.getName().trim().isEmpty())
            throw new IllegalArgumentException("Name cannot be null or empty");

        if (info.getDescription() == null ||
                info.getDescription().trim().isEmpty())
            throw new IllegalArgumentException("Description cannot be null or empty");

        // Check and initialize defaultValue
        //
        if (info.hasDefaultValue()) {
            // Default value not supported for ArrayType and TabularType
            // Cast to Object because "OpenType<T> instanceof" is illegal
            if (openType.isArray() || (Object)openType instanceof TabularType) {
                throw new OpenDataException("Default value not supported " +
                                            "for ArrayType and TabularType");
            }
            // Check defaultValue's class
            if (!openType.isValue(info.getDefaultValue())) {
                final String msg =
                    "Argument defaultValue's class [\"" +
                    info.getDefaultValue().getClass().getName() +
                    "\"] does not match the one defined in openType[\"" +
                    openType.getClassName() +"\"]";
                throw new OpenDataException(msg);
            }
        }

        // Check that we don't have both legalValues and min or max
        //
        if (info.hasLegalValues() &&
                (info.hasMinValue() || info.hasMaxValue())) {
            throw new OpenDataException("cannot have both legalValue and " +
                                        "minValue or maxValue");
        }

        // Check minValue and maxValue
        if (info.hasMinValue() && !openType.isValue(info.getMinValue())) {
            final String msg =
                "Type of minValue [" + info.getMinValue().getClass().getName() +
                "] does not match OpenType [" + openType.getClassName() + "]";
            throw new OpenDataException(msg);
        }
        if (info.hasMaxValue() && !openType.isValue(info.getMaxValue())) {
            final String msg =
                "Type of maxValue [" + info.getMaxValue().getClass().getName() +
                "] does not match OpenType [" + openType.getClassName() + "]";
            throw new OpenDataException(msg);
        }

        // Check that defaultValue is a legal value
        //
        if (info.hasDefaultValue()) {
            Object defaultValue = info.getDefaultValue();
            if (info.hasLegalValues() &&
                    !info.getLegalValues().contains(defaultValue)) {
                throw new OpenDataException("defaultValue is not contained " +
                                            "in legalValues");
            }

            // Check that minValue <= defaultValue <= maxValue
            //
            if (info.hasMinValue()) {
                if (compare(info.getMinValue(), defaultValue) > 0) {
                    throw new OpenDataException("minValue cannot be greater " +
                                                "than defaultValue");
                }
            }
            if (info.hasMaxValue()) {
                if (compare(info.getMaxValue(), defaultValue) < 0) {
                    throw new OpenDataException("maxValue cannot be less " +
                                                "than defaultValue");
                }
            }
        }

        // Check legalValues
        //
        if (info.hasLegalValues()) {
            // legalValues not supported for TabularType and arrays
            if ((Object)openType instanceof TabularType || openType.isArray()) {
                throw new OpenDataException("Legal values not supported " +
                                            "for TabularType and arrays");
            }
            // Check legalValues are valid with openType
            for (Object v : info.getLegalValues()) {
                if (!openType.isValue(v)) {
                    final String msg =
                        "Element of legalValues [" + v +
                        "] is not a valid value for the specified openType [" +
                        openType.toString() +"]";
                    throw new OpenDataException(msg);
                }
            }
        }


        // Check that, if both specified, minValue <= maxValue
        //
        if (info.hasMinValue() && info.hasMaxValue()) {
            if (compare(info.getMinValue(), info.getMaxValue()) > 0) {
                throw new OpenDataException("minValue cannot be greater " +
                                            "than maxValue");
            }
        }

    }

    @SuppressWarnings({"unchecked", "rawtypes"})
    static int compare(Object x, Object y) {
        return ((Comparable) x).compareTo(y);
    }

    static <T> Descriptor makeDescriptor(OpenType<T> openType,
                                         T defaultValue,
                                         T[] legalValues,
                                         Comparable<T> minValue,
                                         Comparable<T> maxValue) {
        Map<String, Object> map = new HashMap<String, Object>();
        if (defaultValue != null)
            map.put("defaultValue", defaultValue);
        if (legalValues != null) {
            Set<T> set = new HashSet<T>();
            for (T v : legalValues)
                set.add(v);
            set = Collections.unmodifiableSet(set);
            map.put("legalValues", set);
        }
        if (minValue != null)
            map.put("minValue", minValue);
        if (maxValue != null)
            map.put("maxValue", maxValue);
        if (map.isEmpty()) {
            return openType.getDescriptor();
        } else {
            map.put("openType", openType);
            return new ImmutableDescriptor(map);
        }
    }

    static <T> Descriptor makeDescriptor(OpenType<T> openType,
                                         T defaultValue,
                                         Set<T> legalValues,
                                         Comparable<T> minValue,
                                         Comparable<T> maxValue) {
        T[] legals;
        if (legalValues == null)
            legals = null;
        else {
            legals = cast(new Object[legalValues.size()]);
            legalValues.toArray(legals);
        }
        return makeDescriptor(openType, defaultValue, legals, minValue, maxValue);
    }


    static <T> T valueFrom(Descriptor d, String name, OpenType<T> openType) {
        Object x = d.getFieldValue(name);
        if (x == null)
            return null;
        try {
            return convertFrom(x, openType);
        } catch (Exception e) {
            final String msg =
                "Cannot convert descriptor field " + name + "  to " +
                openType.getTypeName();
            throw new IllegalArgumentException(msg, e);
        }
    }

    static <T> Set<T> valuesFrom(Descriptor d, String name,
                                 OpenType<T> openType) {
        Object x = d.getFieldValue(name);
        if (x == null)
            return null;
        Collection<?> coll;
        if (x instanceof Set<?>) {
            Set<?> set = (Set<?>) x;
            boolean asis = true;
            for (Object element : set) {
                if (!openType.isValue(element)) {
                    asis = false;
                    break;
                }
            }
            if (asis)
                return cast(set);
            coll = set;
        } else if (x instanceof Object[]) {
            coll = Arrays.asList((Object[]) x);
        } else {
            final String msg =
                "Descriptor value for " + name + " must be a Set or " +
                "an array: " + x.getClass().getName();
            throw new IllegalArgumentException(msg);
        }

        Set<T> result = new HashSet<T>();
        for (Object element : coll)
            result.add(convertFrom(element, openType));
        return result;
    }

    static <T> Comparable<?> comparableValueFrom(Descriptor d, String name,
                                                 OpenType<T> openType) {
        T t = valueFrom(d, name, openType);
        if (t == null || t instanceof Comparable<?>)
            return (Comparable<?>) t;
        final String msg =
            "Descriptor field " + name + " with value " + t +
            " is not Comparable";
        throw new IllegalArgumentException(msg);
    }

    private static <T> T convertFrom(Object x, OpenType<T> openType) {
        if (openType.isValue(x)) {
            T t = OpenMBeanAttributeInfoSupport.<T>cast(x);
            return t;
        }
        return convertFromStrings(x, openType);
    }

    private static <T> T convertFromStrings(Object x, OpenType<T> openType) {
        if (openType instanceof ArrayType<?>)
            return convertFromStringArray(x, openType);
        else if (x instanceof String)
            return convertFromString((String) x, openType);
        final String msg =
            "Cannot convert value " + x + " of type " +
            x.getClass().getName() + " to type " + openType.getTypeName();
        throw new IllegalArgumentException(msg);
    }

    private static <T> T convertFromString(String s, OpenType<T> openType) {
        Class<T> c;
        try {
            String className = openType.safeGetClassName();
            ReflectUtil.checkPackageAccess(className);
            c = cast(Class.forName(className));
        } catch (ClassNotFoundException e) {
            throw new NoClassDefFoundError(e.toString());  // can't happen
        }

        // Look for: public static T valueOf(String)
        Method valueOf;
        try {
            // It is safe to call this plain Class.getMethod because the class "c"
            // was checked before by ReflectUtil.checkPackageAccess(openType.safeGetClassName());
            valueOf = c.getMethod("valueOf", String.class);
            if (!Modifier.isStatic(valueOf.getModifiers()) ||
                    valueOf.getReturnType() != c)
                valueOf = null;
        } catch (NoSuchMethodException e) {
            valueOf = null;
        }
        if (valueOf != null) {
            try {
                return c.cast(MethodUtil.invoke(valueOf, null, new Object[] {s}));
            } catch (Exception e) {
                final String msg =
                    "Could not convert \"" + s + "\" using method: " + valueOf;
                throw new IllegalArgumentException(msg, e);
            }
        }

        // Look for: public T(String)
        Constructor<T> con;
        try {
            // It is safe to call this plain Class.getConstructor because the class "c"
            // was checked before by ReflectUtil.checkPackageAccess(openType.safeGetClassName());
            con = c.getConstructor(String.class);
        } catch (NoSuchMethodException e) {
            con = null;
        }
        if (con != null) {
            try {
                return con.newInstance(s);
            } catch (Exception e) {
                final String msg =
                    "Could not convert \"" + s + "\" using constructor: " + con;
                throw new IllegalArgumentException(msg, e);
            }
        }

        throw new IllegalArgumentException("Don't know how to convert " +
                                           "string to " +
                                           openType.getTypeName());
    }


    /* A Descriptor contained an array value encoded as Strings.  The
       Strings must be organized in an array corresponding to the desired
       array.  If the desired array has n dimensions, so must the String
       array.  We will convert element by element from String to desired
       component type. */
    private static <T> T convertFromStringArray(Object x,
                                                OpenType<T> openType) {
        ArrayType<?> arrayType = (ArrayType<?>) openType;
        OpenType<?> baseType = arrayType.getElementOpenType();
        int dim = arrayType.getDimension();
        String squareBrackets = "[";
        for (int i = 1; i < dim; i++)
            squareBrackets += "[";
        Class<?> stringArrayClass;
        Class<?> targetArrayClass;
        try {
            String baseClassName = baseType.safeGetClassName();

            // check access to the provided base type class name and bail out early
            ReflectUtil.checkPackageAccess(baseClassName);

            stringArrayClass =
                Class.forName(squareBrackets + "Ljava.lang.String;");
            targetArrayClass =
                Class.forName(squareBrackets + "L" + baseClassName + ";");
        } catch (ClassNotFoundException e) {
            throw new NoClassDefFoundError(e.toString());  // can't happen
        }
        if (!stringArrayClass.isInstance(x)) {
            final String msg =
                "Value for " + dim + "-dimensional array of " +
                baseType.getTypeName() + " must be same type or a String " +
                "array with same dimensions";
            throw new IllegalArgumentException(msg);
        }
        OpenType<?> componentOpenType;
        if (dim == 1)
            componentOpenType = baseType;
        else {
            try {
                componentOpenType = new ArrayType<T>(dim - 1, baseType);
            } catch (OpenDataException e) {
                throw new IllegalArgumentException(e.getMessage(), e);
                // can't happen
            }
        }
        int n = Array.getLength(x);
        Object[] targetArray = (Object[])
            Array.newInstance(targetArrayClass.getComponentType(), n);
        for (int i = 0; i < n; i++) {
            Object stringish = Array.get(x, i);  // String or String[] etc
            Object converted =
                convertFromStrings(stringish, componentOpenType);
            Array.set(targetArray, i, converted);
        }
        return OpenMBeanAttributeInfoSupport.<T>cast(targetArray);
    }

    @SuppressWarnings("unchecked")
    static <T> T cast(Object x) {
        return (T) x;
    }

    /**
     * Returns the open type for the values of the attribute described
     * by this {@code OpenMBeanAttributeInfoSupport} instance.
     */
    public OpenType<?> getOpenType() {
        return openType;
    }

    /**
     * Returns the default value for the attribute described by this
     * {@code OpenMBeanAttributeInfoSupport} instance, if specified,
     * or {@code null} otherwise.
     */
    public Object getDefaultValue() {

        // Special case for ArrayType and TabularType
        // [JF] TODO: clone it so that it cannot be altered,
        // [JF] TODO: if we decide to support defaultValue as an array itself.
        // [JF] As of today (oct 2000) it is not supported so
        // defaultValue is null for arrays. Nothing to do.

        return defaultValue;
    }

    /**
     * Returns an unmodifiable Set of legal values for the attribute
     * described by this {@code OpenMBeanAttributeInfoSupport}
     * instance, if specified, or {@code null} otherwise.
     */
    public Set<?> getLegalValues() {

        // Special case for ArrayType and TabularType
        // [JF] TODO: clone values so that they cannot be altered,
        // [JF] TODO: if we decide to support LegalValues as an array itself.
        // [JF] As of today (oct 2000) it is not supported so
        // legalValues is null for arrays. Nothing to do.

        // Returns our legalValues Set (set was constructed unmodifiable)
        return (legalValues);
    }

    /**
     * Returns the minimal value for the attribute described by this
     * {@code OpenMBeanAttributeInfoSupport} instance, if specified,
     * or {@code null} otherwise.
     */
    public Comparable<?> getMinValue() {

        // Note: only comparable values have a minValue,
        // so that's not the case of arrays and tabulars (always null).

        return minValue;
    }

    /**
     * Returns the maximal value for the attribute described by this
     * {@code OpenMBeanAttributeInfoSupport} instance, if specified,
     * or {@code null} otherwise.
     */
    public Comparable<?> getMaxValue() {

        // Note: only comparable values have a maxValue,
        // so that's not the case of arrays and tabulars (always null).

        return maxValue;
    }

    /**
     * Returns {@code true} if this {@code
     * OpenMBeanAttributeInfoSupport} instance specifies a non-null
     * default value for the described attribute, {@code false}
     * otherwise.
     */
    public boolean hasDefaultValue() {

        return (defaultValue != null);
    }

    /**
     * Returns {@code true} if this {@code
     * OpenMBeanAttributeInfoSupport} instance specifies a non-null
     * set of legal values for the described attribute, {@code false}
     * otherwise.
     */
    public boolean hasLegalValues() {

        return (legalValues != null);
    }

    /**
     * Returns {@code true} if this {@code
     * OpenMBeanAttributeInfoSupport} instance specifies a non-null
     * minimal value for the described attribute, {@code false}
     * otherwise.
     */
    public boolean hasMinValue() {

        return (minValue != null);
    }

    /**
     * Returns {@code true} if this {@code
     * OpenMBeanAttributeInfoSupport} instance specifies a non-null
     * maximal value for the described attribute, {@code false}
     * otherwise.
     */
    public boolean hasMaxValue() {

        return (maxValue != null);
    }


    /**
     * Tests whether {@code obj} is a valid value for the attribute
     * described by this {@code OpenMBeanAttributeInfoSupport}
     * instance.
     *
     * @param obj the object to be tested.
     *
     * @return {@code true} if {@code obj} is a valid value for
     * the parameter described by this {@code
     * OpenMBeanAttributeInfoSupport} instance, {@code false}
     * otherwise.
     */
    public boolean isValue(Object obj) {
        return isValue(this, obj);
    }

    @SuppressWarnings({"unchecked", "rawtypes"})  // cast to Comparable
    static boolean isValue(OpenMBeanParameterInfo info, Object obj) {
        if (info.hasDefaultValue() && obj == null)
            return true;
        return
            info.getOpenType().isValue(obj) &&
            (!info.hasLegalValues() || info.getLegalValues().contains(obj)) &&
            (!info.hasMinValue() ||
            ((Comparable) info.getMinValue()).compareTo(obj) <= 0) &&
            (!info.hasMaxValue() ||
            ((Comparable) info.getMaxValue()).compareTo(obj) >= 0);
    }

    /* ***  Commodity methods from java.lang.Object  *** */


    /**
     * Compares the specified {@code obj} parameter with this {@code
     * OpenMBeanAttributeInfoSupport} instance for equality.
     * <p>
     * Returns {@code true} if and only if all of the following statements are true:
     * <ul>
     * <li>{@code obj} is non null,</li>
     * <li>{@code obj} also implements the {@code OpenMBeanAttributeInfo} interface,</li>
     * <li>their names are equal</li>
     * <li>their open types are equal</li>
     * <li>their access properties (isReadable, isWritable and isIs) are equal</li>
     * <li>their default, min, max and legal values are equal.</li>
     * </ul>
     * This ensures that this {@code equals} method works properly for
     * {@code obj} parameters which are different implementations of
     * the {@code OpenMBeanAttributeInfo} interface.
     *
     * <p>If {@code obj} also implements {@link DescriptorRead}, then its
     * {@link DescriptorRead#getDescriptor() getDescriptor()} method must
     * also return the same value as for this object.</p>
     *
     * @param obj the object to be compared for equality with this
     * {@code OpenMBeanAttributeInfoSupport} instance.
     *
     * @return {@code true} if the specified object is equal to this
     * {@code OpenMBeanAttributeInfoSupport} instance.
     */
    public boolean equals(Object obj) {
        if (!(obj instanceof OpenMBeanAttributeInfo))
            return false;

        OpenMBeanAttributeInfo other = (OpenMBeanAttributeInfo) obj;

        return
            this.isReadable() == other.isReadable() &&
            this.isWritable() == other.isWritable() &&
            this.isIs() == other.isIs() &&
            equal(this, other);
    }

    static boolean equal(OpenMBeanParameterInfo x1, OpenMBeanParameterInfo x2) {
        if (x1 instanceof DescriptorRead) {
            if (!(x2 instanceof DescriptorRead))
                return false;
            Descriptor d1 = ((DescriptorRead) x1).getDescriptor();
            Descriptor d2 = ((DescriptorRead) x2).getDescriptor();
            if (!d1.equals(d2))
                return false;
        } else if (x2 instanceof DescriptorRead)
            return false;

        return
            x1.getName().equals(x2.getName()) &&
            x1.getOpenType().equals(x2.getOpenType()) &&
            (x1.hasDefaultValue() ?
                x1.getDefaultValue().equals(x2.getDefaultValue()) :
                !x2.hasDefaultValue()) &&
            (x1.hasMinValue() ?
                x1.getMinValue().equals(x2.getMinValue()) :
                !x2.hasMinValue()) &&
            (x1.hasMaxValue() ?
                x1.getMaxValue().equals(x2.getMaxValue()) :
                !x2.hasMaxValue()) &&
            (x1.hasLegalValues() ?
                x1.getLegalValues().equals(x2.getLegalValues()) :
                !x2.hasLegalValues());
    }

    /**
     * <p>Returns the hash code value for this {@code
     * OpenMBeanAttributeInfoSupport} instance.</p>
     *
     * <p>The hash code of an {@code OpenMBeanAttributeInfoSupport}
     * instance is the sum of the hash codes of all elements of
     * information used in {@code equals} comparisons (ie: its name,
     * its <i>open type</i>, its default, min, max and legal
     * values, and its Descriptor).
     *
     * <p>This ensures that {@code t1.equals(t2)} implies that {@code
     * t1.hashCode()==t2.hashCode()} for any two {@code
     * OpenMBeanAttributeInfoSupport} instances {@code t1} and {@code
     * t2}, as required by the general contract of the method {@link
     * Object#hashCode() Object.hashCode()}.
     *
     * <p>However, note that another instance of a class implementing
     * the {@code OpenMBeanAttributeInfo} interface may be equal to
     * this {@code OpenMBeanAttributeInfoSupport} instance as defined
     * by {@link #equals(java.lang.Object)}, but may have a different
     * hash code if it is calculated differently.
     *
     * <p>As {@code OpenMBeanAttributeInfoSupport} instances are
     * immutable, the hash code for this instance is calculated once,
     * on the first call to {@code hashCode}, and then the same value
     * is returned for subsequent calls.
     *
     * @return the hash code value for this {@code
     * OpenMBeanAttributeInfoSupport} instance
     */
    public int hashCode() {

        // Calculate the hash code value if it has not yet been done
        // (ie 1st call to hashCode())
        //
        if (myHashCode == null)
            myHashCode = hashCode(this);

        // return always the same hash code for this instance (immutable)
        //
        return myHashCode.intValue();
    }

    static int hashCode(OpenMBeanParameterInfo info) {
        int value = 0;
        value += info.getName().hashCode();
        value += info.getOpenType().hashCode();
        if (info.hasDefaultValue())
            value += info.getDefaultValue().hashCode();
        if (info.hasMinValue())
            value += info.getMinValue().hashCode();
        if (info.hasMaxValue())
            value += info.getMaxValue().hashCode();
        if (info.hasLegalValues())
            value += info.getLegalValues().hashCode();
        if (info instanceof DescriptorRead)
            value += ((DescriptorRead) info).getDescriptor().hashCode();
        return value;
    }

    /**
     * Returns a string representation of this
     * {@code OpenMBeanAttributeInfoSupport} instance.
     * <p>
     * The string representation consists of the name of this class (i.e.
     * {@code javax.management.openmbean.OpenMBeanAttributeInfoSupport}),
     * the string representation of the name and open type of the
     * described parameter, the string representation of its
     * default, min, max and legal values and the string
     * representation of its descriptor.
     *
     * <p>As {@code OpenMBeanAttributeInfoSupport} instances are
     * immutable, the string representation for this instance is
     * calculated once, on the first call to {@code toString}, and
     * then the same value is returned for subsequent calls.
     *
     * @return a string representation of this
     * {@code OpenMBeanAttributeInfoSupport} instance.
     */
    public String toString() {

        // Calculate the string value if it has not yet been done
        // (ie 1st call to toString())
        //
        if (myToString == null)
            myToString = toString(this);

        // return always the same string representation for this
        // instance (immutable)
        //
        return myToString;
    }

    static String toString(OpenMBeanParameterInfo info) {
        Descriptor d = (info instanceof DescriptorRead) ?
            ((DescriptorRead) info).getDescriptor() : null;
        return
            info.getClass().getName() +
            "(name=" + info.getName() +
            ",openType=" + info.getOpenType() +
            ",default=" + info.getDefaultValue() +
            ",minValue=" + info.getMinValue() +
            ",maxValue=" + info.getMaxValue() +
            ",legalValues=" + info.getLegalValues() +
            ((d == null) ? "" : ",descriptor=" + d) +
            ")";
    }
}