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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

 *

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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:</p>

 *

 * <pre>

 * @Documented

 * @Target(ElementType.METHOD)

 * @Retention(RetentionPolicy.RUNTIME)

 * public @interface Units {

 *     <b>&#64;DescriptorKey("units")</b>

 *     String value();

 * }

 * </pre>

 *

 * <p>and this use of the annotation:</p>

 *

 * <pre>

 * public interface CacheControlMBean {

 *     <b>&#64;Units("bytes")</b>

 *     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:</p>

 *

 * <pre>

 * @Documented

 * @Target(ElementType.METHOD)

 * @Retention(RetentionPolicy.RUNTIME)

 * public @interface Units {

 *     <b>&#64;DescriptorKey("units")</b>

 *     String value();

 *

 *     <b>&#64;DescriptorKey("descriptionResourceKey")</b>

 *     String resourceKey() default "";

 *

 *     <b>&#64;DescriptorKey("descriptionResourceBundleBaseName")</b>

 *     String resourceBundleBaseName() default "";

 * }

 * </pre>

 *

 * <p>and it is used like this:</p>

 *

 * <pre>

 * public interface CacheControlMBean {

 *     <b>&#64;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><th>Name</th><th>Value</th></tr>

 * <tr><td>units</td><td>"bytes"</td></tr>

 * <tr><td>descriptionResourceKey</td><td>"bytes.key"</td></tr>

 * <tr><td>descriptionResourceBundleBaseName</td>

 *     <td>"com.example.foo.MBeanResources"</td></tr>

 * </table>

 *

 * <p>An annotation such as {@code @Units} can be applied to:</p>

 *

 * <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>

 *

 * <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><th>Annotation element</th><th>Descriptor field</th></tr>

 * <tr><td>Primitive value ({@code 5}, {@code false}, etc)</td>

 *     <td>Wrapped value ({@code Integer.valueOf(5)},

 *         {@code Boolean.FALSE}, etc)</td></tr>

 * <tr><td>Class constant (e.g. {@code Thread.class})</td>

 *     <td>Class name from Class.getName()

 *         (e.g. {@code "java.lang.Thread"})</td></tr>

 * <tr><td>Enum constant (e.g. ElementType.FIELD)</td>

 *     <td>Constant name from Enum.name()

 *         (e.g. {@code "FIELD"})</td></tr>

 * <tr><td>Array of class constants or enum constants</td>

 *     <td>String array derived by applying these rules to each

 *         element</td></tr>

 * <tr><td>Value of any other type<br>

 *         ({@code String}, {@code String[]}, {@code int[]}, etc)</td>

 *     <td>The same value</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>&#64;DescriptorKey(value = "descriptionResourceKey",

     *                    omitIfDefault = true)</b>

     *     String resourceKey() default "";

     *

     *     <b>&#64;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;

}