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| 1 | /* | ||
| 2 | * Copyright (c) 2005, 2008, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package javax.management; | ||
| 27 | |||
| 28 | import java.lang.annotation.*; | ||
| 29 | |||
| 30 | /** | ||
| 31 | * <p>Meta-annotation that describes how an annotation element relates | ||
| 32 | * to a field in a {@link Descriptor}. This can be the Descriptor for | ||
| 33 | * an MBean, or for an attribute, operation, or constructor in an | ||
| 34 | * MBean, or for a parameter of an operation or constructor.</p> | ||
| 35 | * | ||
| 36 | * <p>Consider this annotation for example:</p> | ||
| 37 | * | ||
| 38 | * <pre> | ||
| 39 | * @Documented | ||
| 40 | * @Target(ElementType.METHOD) | ||
| 41 | * @Retention(RetentionPolicy.RUNTIME) | ||
| 42 | * public @interface Units { | ||
| 43 | * <b>@DescriptorKey("units")</b> | ||
| 44 | * String value(); | ||
| 45 | * } | ||
| 46 | * </pre> | ||
| 47 | * | ||
| 48 | * <p>and this use of the annotation:</p> | ||
| 49 | * | ||
| 50 | * <pre> | ||
| 51 | * public interface CacheControlMBean { | ||
| 52 | * <b>@Units("bytes")</b> | ||
| 53 | * public long getCacheSize(); | ||
| 54 | * } | ||
| 55 | * </pre> | ||
| 56 | * | ||
| 57 | * <p>When a Standard MBean is made from the {@code CacheControlMBean}, | ||
| 58 | * the usual rules mean that it will have an attribute called | ||
| 59 | * {@code CacheSize} of type {@code long}. The {@code @Units} | ||
| 60 | * annotation, given the above definition, will ensure that the | ||
| 61 | * {@link MBeanAttributeInfo} for this attribute will have a | ||
| 62 | * {@code Descriptor} that has a field called {@code units} with | ||
| 63 | * corresponding value {@code bytes}.</p> | ||
| 64 | * | ||
| 65 | * <p>Similarly, if the annotation looks like this:</p> | ||
| 66 | * | ||
| 67 | * <pre> | ||
| 68 | * @Documented | ||
| 69 | * @Target(ElementType.METHOD) | ||
| 70 | * @Retention(RetentionPolicy.RUNTIME) | ||
| 71 | * public @interface Units { | ||
| 72 | * <b>@DescriptorKey("units")</b> | ||
| 73 | * String value(); | ||
| 74 | * | ||
| 75 | * <b>@DescriptorKey("descriptionResourceKey")</b> | ||
| 76 | * String resourceKey() default ""; | ||
| 77 | * | ||
| 78 | * <b>@DescriptorKey("descriptionResourceBundleBaseName")</b> | ||
| 79 | * String resourceBundleBaseName() default ""; | ||
| 80 | * } | ||
| 81 | * </pre> | ||
| 82 | * | ||
| 83 | * <p>and it is used like this:</p> | ||
| 84 | * | ||
| 85 | * <pre> | ||
| 86 | * public interface CacheControlMBean { | ||
| 87 | * <b>@Units("bytes", | ||
| 88 | * resourceKey="bytes.key", | ||
| 89 | * resourceBundleBaseName="com.example.foo.MBeanResources")</b> | ||
| 90 | * public long getCacheSize(); | ||
| 91 | * } | ||
| 92 | * </pre> | ||
| 93 | * | ||
| 94 | * <p>then the resulting {@code Descriptor} will contain the following | ||
| 95 | * fields:</p> | ||
| 96 | * | ||
| 97 | * <table border="2"> | ||
| 98 | * <tr><th>Name</th><th>Value</th></tr> | ||
| 99 | * <tr><td>units</td><td>"bytes"</td></tr> | ||
| 100 | * <tr><td>descriptionResourceKey</td><td>"bytes.key"</td></tr> | ||
| 101 | * <tr><td>descriptionResourceBundleBaseName</td> | ||
| 102 | * <td>"com.example.foo.MBeanResources"</td></tr> | ||
| 103 | * </table> | ||
| 104 | * | ||
| 105 | * <p>An annotation such as {@code @Units} can be applied to:</p> | ||
| 106 | * | ||
| 107 | * <ul> | ||
| 108 | * <li>a Standard MBean or MXBean interface; | ||
| 109 | * <li>a method in such an interface; | ||
| 110 | * <li>a parameter of a method in a Standard MBean or MXBean interface | ||
| 111 | * when that method is an operation (not a getter or setter for an attribute); | ||
| 112 | * <li>a public constructor in the class that implements a Standard MBean | ||
| 113 | * or MXBean; | ||
| 114 | * <li>a parameter in such a constructor. | ||
| 115 | * </ul> | ||
| 116 | * | ||
| 117 | * <p>Other uses of the annotation are ignored.</p> | ||
| 118 | * | ||
| 119 | * <p>Interface annotations are checked only on the exact interface | ||
| 120 | * that defines the management interface of a Standard MBean or an | ||
| 121 | * MXBean, not on its parent interfaces. Method annotations are | ||
| 122 | * checked only in the most specific interface in which the method | ||
| 123 | * appears; in other words, if a child interface overrides a method | ||
| 124 | * from a parent interface, only {@code @DescriptorKey} annotations in | ||
| 125 | * the method in the child interface are considered. | ||
| 126 | * | ||
| 127 | * <p>The Descriptor fields contributed in this way by different | ||
| 128 | * annotations on the same program element must be consistent. That | ||
| 129 | * is, two different annotations, or two members of the same | ||
| 130 | * annotation, must not define a different value for the same | ||
| 131 | * Descriptor field. Fields from annotations on a getter method must | ||
| 132 | * also be consistent with fields from annotations on the | ||
| 133 | * corresponding setter method.</p> | ||
| 134 | * | ||
| 135 | * <p>The Descriptor resulting from these annotations will be merged | ||
| 136 | * with any Descriptor fields provided by the implementation, such as | ||
| 137 | * the <a href="Descriptor.html#immutableInfo">{@code | ||
| 138 | * immutableInfo}</a> field for an MBean. The fields from the annotations | ||
| 139 | * must be consistent with these fields provided by the implementation.</p> | ||
| 140 | * | ||
| 141 | * <p>An annotation element to be converted into a descriptor field | ||
| 142 | * can be of any type allowed by the Java language, except an annotation | ||
| 143 | * or an array of annotations. The value of the field is derived from | ||
| 144 | * the value of the annotation element as follows:</p> | ||
| 145 | * | ||
| 146 | * <table border="2"> | ||
| 147 | * <tr><th>Annotation element</th><th>Descriptor field</th></tr> | ||
| 148 | * <tr><td>Primitive value ({@code 5}, {@code false}, etc)</td> | ||
| 149 | * <td>Wrapped value ({@code Integer.valueOf(5)}, | ||
| 150 | * {@code Boolean.FALSE}, etc)</td></tr> | ||
| 151 | * <tr><td>Class constant (e.g. {@code Thread.class})</td> | ||
| 152 | * <td>Class name from {@link Class#getName()} | ||
| 153 | * (e.g. {@code "java.lang.Thread"})</td></tr> | ||
| 154 | * <tr><td>Enum constant (e.g. {@link ElementType#FIELD})</td> | ||
| 155 | * <td>Constant name from {@link Enum#name()} | ||
| 156 | * (e.g. {@code "FIELD"})</td></tr> | ||
| 157 | * <tr><td>Array of class constants or enum constants</td> | ||
| 158 | * <td>String array derived by applying these rules to each | ||
| 159 | * element</td></tr> | ||
| 160 | * <tr><td>Value of any other type<br> | ||
| 161 | * ({@code String}, {@code String[]}, {@code int[]}, etc)</td> | ||
| 162 | * <td>The same value</td></tr> | ||
| 163 | * </table> | ||
| 164 | * | ||
| 165 | * @since 1.6 | ||
| 166 | */ | ||
| 167 | @Documented | ||
| 168 | @Retention(RetentionPolicy.RUNTIME) | ||
| 169 | @Target(ElementType.METHOD) | ||
| 170 | public @interface DescriptorKey { | ||
| 171 | String value(); | ||
| 172 | } | ||