Java tutorial
/* * 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 * or visit www.oracle.com if you need additional information or have any * questions. */ 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; } }