management/openmbean/OpenMBeanInfoSupport.java

/*
 * Copyright (c) 2000, 2013, 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
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 * questions.
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package javax.management.openmbean;


// java import
//
import java.util.Arrays;
import java.util.HashSet;
import java.util.Objects;

import javax.management.Descriptor;
import javax.management.MBeanAttributeInfo;
import javax.management.MBeanConstructorInfo;
import javax.management.MBeanInfo;
import javax.management.MBeanNotificationInfo;
import javax.management.MBeanOperationInfo;

/**
 * The {@code OpenMBeanInfoSupport} class describes the management
 * information of an <i>open MBean</i>: it is a subclass of {@link
 * javax.management.MBeanInfo}, and it implements the {@link
 * OpenMBeanInfo} interface.  Note that an <i>open MBean</i> is
 * recognized as such if its {@code getMBeanInfo()} method returns an
 * instance of a class which implements the OpenMBeanInfo interface,
 * typically {@code OpenMBeanInfoSupport}.
 *
 *
 * @since 1.5
 */
public class OpenMBeanInfoSupport
    extends MBeanInfo
    implements OpenMBeanInfo {

    /* Serial version */
    static final long serialVersionUID = 4349395935420511492L;

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


    /**
     * <p>Constructs an {@code OpenMBeanInfoSupport} instance, which
     * describes a class of open MBeans with the specified {@code
     * className}, {@code description}, {@code openAttributes}, {@code
     * openConstructors} , {@code openOperations} and {@code
     * notifications}.</p>
     *
     * <p>The {@code openAttributes}, {@code openConstructors},
     * {@code openOperations} and {@code notifications}
     * array parameters are internally copied, so that subsequent changes
     * to the arrays referenced by these parameters have no effect on this
     * instance.</p>
     *
     * @param className The fully qualified Java class name of the
     * open MBean described by this <CODE>OpenMBeanInfoSupport</CODE>
     * instance.
     *
     * @param description A human readable description of the open
     * MBean described by this <CODE>OpenMBeanInfoSupport</CODE>
     * instance.
     *
     * @param openAttributes The list of exposed attributes of the
     * described open MBean; Must be an array of instances of a
     * subclass of {@code MBeanAttributeInfo}, typically {@code
     * OpenMBeanAttributeInfoSupport}.
     *
     * @param openConstructors The list of exposed public constructors
     * of the described open MBean; Must be an array of instances of a
     * subclass of {@code MBeanConstructorInfo}, typically {@code
     * OpenMBeanConstructorInfoSupport}.
     *
     * @param openOperations The list of exposed operations of the
     * described open MBean.  Must be an array of instances of a
     * subclass of {@code MBeanOperationInfo}, typically {@code
     * OpenMBeanOperationInfoSupport}.
     *
     * @param notifications The list of notifications emitted by the
     * described open MBean.
     *
     * @throws ArrayStoreException If {@code openAttributes}, {@code
     * openConstructors} or {@code openOperations} is not an array of
     * instances of a subclass of {@code MBeanAttributeInfo}, {@code
     * MBeanConstructorInfo} or {@code MBeanOperationInfo}
     * respectively.
     */
    public OpenMBeanInfoSupport(String className,
                                String description,
                                OpenMBeanAttributeInfo[] openAttributes,
                                OpenMBeanConstructorInfo[] openConstructors,
                                OpenMBeanOperationInfo[] openOperations,
                                MBeanNotificationInfo[] notifications) {
        this(className, description,
             openAttributes, openConstructors, openOperations, notifications,
             (Descriptor) null);
    }

    /**
     * <p>Constructs an {@code OpenMBeanInfoSupport} instance, which
     * describes a class of open MBeans with the specified {@code
     * className}, {@code description}, {@code openAttributes}, {@code
     * openConstructors} , {@code openOperations}, {@code
     * notifications}, and {@code descriptor}.</p>
     *
     * <p>The {@code openAttributes}, {@code openConstructors}, {@code
     * openOperations} and {@code notifications} array parameters are
     * internally copied, so that subsequent changes to the arrays
     * referenced by these parameters have no effect on this
     * instance.</p>
     *
     * @param className The fully qualified Java class name of the
     * open MBean described by this <CODE>OpenMBeanInfoSupport</CODE>
     * instance.
     *
     * @param description A human readable description of the open
     * MBean described by this <CODE>OpenMBeanInfoSupport</CODE>
     * instance.
     *
     * @param openAttributes The list of exposed attributes of the
     * described open MBean; Must be an array of instances of a
     * subclass of {@code MBeanAttributeInfo}, typically {@code
     * OpenMBeanAttributeInfoSupport}.
     *
     * @param openConstructors The list of exposed public constructors
     * of the described open MBean; Must be an array of instances of a
     * subclass of {@code MBeanConstructorInfo}, typically {@code
     * OpenMBeanConstructorInfoSupport}.
     *
     * @param openOperations The list of exposed operations of the
     * described open MBean.  Must be an array of instances of a
     * subclass of {@code MBeanOperationInfo}, typically {@code
     * OpenMBeanOperationInfoSupport}.
     *
     * @param notifications The list of notifications emitted by the
     * described open MBean.
     *
     * @param descriptor The descriptor for the MBean.  This may be null
     * which is equivalent to an empty descriptor.
     *
     * @throws ArrayStoreException If {@code openAttributes}, {@code
     * openConstructors} or {@code openOperations} is not an array of
     * instances of a subclass of {@code MBeanAttributeInfo}, {@code
     * MBeanConstructorInfo} or {@code MBeanOperationInfo}
     * respectively.
     *
     * @since 1.6
     */
    public OpenMBeanInfoSupport(String className,
                                String description,
                                OpenMBeanAttributeInfo[] openAttributes,
                                OpenMBeanConstructorInfo[] openConstructors,
                                OpenMBeanOperationInfo[] openOperations,
                                MBeanNotificationInfo[] notifications,
                                Descriptor descriptor) {
        super(className,
              description,
              attributeArray(openAttributes),
              constructorArray(openConstructors),
              operationArray(openOperations),
              (notifications == null) ? null : notifications.clone(),
              descriptor);
    }


    private static MBeanAttributeInfo[]
            attributeArray(OpenMBeanAttributeInfo[] src) {
        if (src == null)
            return null;
        MBeanAttributeInfo[] dst = new MBeanAttributeInfo[src.length];
        System.arraycopy(src, 0, dst, 0, src.length);
        // may throw an ArrayStoreException
        return dst;
    }

    private static MBeanConstructorInfo[]
            constructorArray(OpenMBeanConstructorInfo[] src) {
        if (src == null)
            return null;
        MBeanConstructorInfo[] dst = new MBeanConstructorInfo[src.length];
        System.arraycopy(src, 0, dst, 0, src.length);
        // may throw an ArrayStoreException
        return dst;
    }

    private static MBeanOperationInfo[]
            operationArray(OpenMBeanOperationInfo[] src) {
        if (src == null)
            return null;
        MBeanOperationInfo[] dst = new MBeanOperationInfo[src.length];
        System.arraycopy(src, 0, dst, 0, src.length);
        return dst;
    }


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


    /**
     * <p>Compares the specified {@code obj} parameter with this
     * {@code OpenMBeanInfoSupport} instance for equality.</p>
     *
     * <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 OpenMBeanInfo}
     * interface,</li>
     * <li>their class names are equal</li>
     * <li>their infos on attributes, constructors, operations and
     * notifications are equal</li>
     * </ul>
     *
     * This ensures that this {@code equals} method works properly for
     * {@code obj} parameters which are different implementations of
     * the {@code OpenMBeanInfo} interface.
     *
     * @param obj the object to be compared for equality with this
     * {@code OpenMBeanInfoSupport} instance;
     *
     * @return {@code true} if the specified object is equal to this
     * {@code OpenMBeanInfoSupport} instance.
     */
    public boolean equals(Object obj) {

        // if obj is null, return false
        //
        if (obj == null) {
            return false;
        }

        // if obj is not a OpenMBeanInfo, return false
        //
        OpenMBeanInfo other;
        try {
            other = (OpenMBeanInfo) obj;
        } catch (ClassCastException e) {
            return false;
        }

        // Now, really test for equality between this OpenMBeanInfo
        // implementation and the other:
        //

        // their MBean className should be equal
        if (!Objects.equals(this.getClassName(), other.getClassName())) {
            return false;
        }

        // their infos on attributes should be equal (order not
        // significant => equality between sets, not arrays or lists)
        if (!sameArrayContents(this.getAttributes(), other.getAttributes()))
            return false;

        // their infos on constructors should be equal (order not
        // significant => equality between sets, not arrays or lists)
        if (!sameArrayContents(this.getConstructors(), other.getConstructors()))
            return false;

        // their infos on operations should be equal (order not
        // significant => equality between sets, not arrays or lists)
        if (!sameArrayContents(this.getOperations(), other.getOperations()))

            return false;

        // their infos on notifications should be equal (order not
        // significant => equality between sets, not arrays or lists)
        if (!sameArrayContents(this.getNotifications(), other.getNotifications()))
            return false;

        // All tests for equality were successful
        //
        return true;
    }

    private static <T> boolean sameArrayContents(T[] a1, T[] a2) {
        return (new HashSet<T>(Arrays.asList(a1))
                .equals(new HashSet<T>(Arrays.asList(a2))));
    }

    /**
     * <p>Returns the hash code value for this {@code
     * OpenMBeanInfoSupport} instance.</p>
     *
     * <p>The hash code of an {@code OpenMBeanInfoSupport} instance is
     * the sum of the hash codes of all elements of information used
     * in {@code equals} comparisons (ie: its class name, and its
     * infos on attributes, constructors, operations and
     * notifications, where the hashCode of each of these arrays is
     * calculated by a call to {@code new
     * java.util.HashSet(java.util.Arrays.asList(this.getSignature)).hashCode()}).</p>
     *
     * <p>This ensures that {@code t1.equals(t2)} implies that {@code
     * t1.hashCode()==t2.hashCode()} for any two {@code
     * OpenMBeanInfoSupport} instances {@code t1} and {@code t2}, as
     * required by the general contract of the method {@link
     * Object#hashCode() Object.hashCode()}.</p>
     *
     * <p>However, note that another instance of a class implementing
     * the {@code OpenMBeanInfo} interface may be equal to this {@code
     * OpenMBeanInfoSupport} instance as defined by {@link
     * #equals(java.lang.Object)}, but may have a different hash code
     * if it is calculated differently.</p>
     *
     * <p>As {@code OpenMBeanInfoSupport} 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.</p>
     *
     * @return the hash code value for this {@code
     * OpenMBeanInfoSupport} instance
     */
    public int hashCode() {

        // Calculate the hash code value if it has not yet been done
        // (ie 1st call to hashCode())
        //
        if (myHashCode == null) {
            int value = 0;
            if (this.getClassName() != null) {
                value += this.getClassName().hashCode();
            }
            value += arraySetHash(this.getAttributes());
            value += arraySetHash(this.getConstructors());
            value += arraySetHash(this.getOperations());
            value += arraySetHash(this.getNotifications());
            myHashCode = Integer.valueOf(value);
        }

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

    private static <T> int arraySetHash(T[] a) {
        return new HashSet<T>(Arrays.asList(a)).hashCode();
    }


    /**
     * <p>Returns a string representation of this {@code
     * OpenMBeanInfoSupport} instance.</p>
     *
     * <p>The string representation consists of the name of this class
     * (ie {@code javax.management.openmbean.OpenMBeanInfoSupport}),
     * the MBean class name, the string representation of infos on
     * attributes, constructors, operations and notifications of the
     * described MBean and the string representation of the descriptor.</p>
     *
     * <p>As {@code OpenMBeanInfoSupport} 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.</p>
     *
     * @return a string representation of this {@code
     * OpenMBeanInfoSupport} instance
     */
    public String toString() {

        // Calculate the string value if it has not yet been done (ie
        // 1st call to toString())
        //
        if (myToString == null) {
            myToString = new StringBuilder()
                .append(this.getClass().getName())
                .append("(mbean_class_name=")
                .append(this.getClassName())
                .append(",attributes=")
                .append(Arrays.asList(this.getAttributes()).toString())
                .append(",constructors=")
                .append(Arrays.asList(this.getConstructors()).toString())
                .append(",operations=")
                .append(Arrays.asList(this.getOperations()).toString())
                .append(",notifications=")
                .append(Arrays.asList(this.getNotifications()).toString())
                .append(",descriptor=")
                .append(this.getDescriptor())
                .append(")")
                .toString();
        }

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

}