* <tr> * <tr> * <tr> * <td>"com.example.foo.MBeanResources" * </table> * * <p>An annotation such as {@code @Units} can be applied to:

* * <ul> * <li>a Standard MBean or MXBean interface; * <li>a method in such an interface; * <li>a parameter of a method in a Standard MBean or MXBean interface * when that method is an operation (not a getter or setter for an attribute); * <li>a public constructor in the class that implements a Standard MBean * or MXBean; * <li>a parameter in such a constructor. * </ul> * * <p>Other uses of the annotation are ignored.

* * <p>Interface annotations are checked only on the exact interface * that defines the management interface of a Standard MBean or an * MXBean, not on its parent interfaces. Method annotations are * checked only in the most specific interface in which the method * appears; in other words, if a child interface overrides a method * from a parent interface, only {@code @DescriptorKey} annotations in * the method in the child interface are considered. * * <p>The Descriptor fields contributed in this way by different * annotations on the same program element must be consistent with * each other and with any fields contributed by a * DescriptorFields annotation. That is, two * different annotations, or two members of the same annotation, must * not define a different value for the same Descriptor field. Fields * from annotations on a getter method must also be consistent with * fields from annotations on the corresponding setter method.</p> * * <p>The Descriptor resulting from these annotations will be merged * with any Descriptor fields provided by the implementation, such as * the <a href="Descriptor.html#immutableInfo">{@code * immutableInfo}</a> field for an MBean. The fields from the annotations * must be consistent with these fields provided by the implementation.</p> * * <p>An annotation element to be converted into a descriptor field * can be of any type allowed by the Java language, except an annotation * or an array of annotations. The value of the field is derived from * the value of the annotation element as follows:</p> * * <table border="2"> * <tr> * <tr> * <td>Wrapped value ({@code Integer.valueOf(5)}, * {@code Boolean.FALSE}, etc)</td> * <tr> * <td>Class name from Class.getName() * (e.g. {@code "java.lang.Thread"})</td> * <tr> * <td>Constant name from Enum.name() * (e.g. {@code "FIELD"})</td> * <tr> * <td>String array derived by applying these rules to each * element</td> * <tr> * </table> * * @since 1.6 */ @Documented @Retention(RetentionPolicy.RUNTIME) @Target({ ElementType.METHOD, ElementType.FIELD }) public @interface DescriptorKey { String value(); /** * <p>Do not include this field in the Descriptor if the annotation * element has its default value. For example, suppose {@code @Units} is * defined like this:</p> * * <pre> * @Documented * @Target(ElementType.METHOD) * @Retention(RetentionPolicy.RUNTIME) * public @interface Units { * @DescriptorKey("units") * String value(); * * <b>@DescriptorKey(value = "descriptionResourceKey", * omitIfDefault = true)</b> * String resourceKey() default ""; * * <b>@DescriptorKey(value = "descriptionResourceBundleBaseName", * omitIfDefault = true)</b> * String resourceBundleBaseName() default ""; * } * </pre> * * <p>Then consider a usage such as {@code @Units("bytes")} or * {@code @Units(value = "bytes", resourceKey = "")}, where the * {@code resourceKey} and {@code resourceBundleBaseNames} elements * have their default values. In this case the Descriptor resulting * from these annotations will not include a {@code descriptionResourceKey} * or {@code descriptionResourceBundleBaseName} field.</p> */ boolean omitIfDefault() default false; }

	Java example source code file (DescriptorKey.java) This example Java source code file (DescriptorKey.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM. Learn more about this Java project at its project page. Java - Java tags/keywords annotation, descriptorkey, documented, string, target The DescriptorKey.java Java example source code /* * Copyright (c) 2005, 2010, 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 com.sun.org.glassfish.gmbal; import java.lang.annotation.*; /** This is taken directly from JDK 7 in order to support this feature in * JDK 5. * * <p>Meta-annotation that describes how an annotation element relates * to a field in a Descriptor. This can be the Descriptor for * an MBean, or for an attribute, operation, or constructor in an * MBean, or for a parameter of an operation or constructor.</p> * * <p>(The DescriptorFields annotation * provides another way to add fields to a {@code Descriptor}. See * the documentation for that annotation for a comparison of the * two possibilities.)</p> * * <p>Consider this annotation for example: * * <pre> * @Documented * @Target(ElementType.METHOD) * @Retention(RetentionPolicy.RUNTIME) * public @interface Units { * <b>@DescriptorKey("units") * String value(); * } * </pre> * * <p>and this use of the annotation: * * <pre> * public interface CacheControlMBean { * <b>@Units("bytes") * public long getCacheSize(); * } * </pre> * * <p>When a Standard MBean is made from the {@code CacheControlMBean}, * the usual rules mean that it will have an attribute called * {@code CacheSize} of type {@code long}. The {@code @Units} * annotation, given the above definition, will ensure that the * MBeanAttributeInfo for this attribute will have a * {@code Descriptor} that has a field called {@code units} with * corresponding value {@code bytes}.</p> * * <p>Similarly, if the annotation looks like this: * * <pre> * @Documented * @Target(ElementType.METHOD) * @Retention(RetentionPolicy.RUNTIME) * public @interface Units { * <b>@DescriptorKey("units") * String value(); * * <b>@DescriptorKey("descriptionResourceKey") * String resourceKey() default ""; * * <b>@DescriptorKey("descriptionResourceBundleBaseName") * String resourceBundleBaseName() default ""; * } * </pre> * * <p>and it is used like this: * * <pre> * public interface CacheControlMBean { * <b>@Units("bytes", * resourceKey="bytes.key", * resourceBundleBaseName="com.example.foo.MBeanResources")</b> * public long getCacheSize(); * } * </pre> * * <p>then the resulting {@code Descriptor} will contain the following * fields:</p> * * <table border="2"> * <tr>	Name	Value
units	"bytes"
descriptionResourceKey	"bytes.key"
descriptionResourceBundleBaseName
Annotation element	Descriptor field
Primitive value ({@code 5}, {@code false}, etc)
Class constant (e.g. {@code Thread.class})
Enum constant (e.g. ElementType.FIELD)
Array of class constants or enum constants
Value of any other type * ({@code String}, {@code String[]}, {@code int[]}, etc)</td> * <td>The same value

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