/*

 * Copyright (c) 2016, 2018, 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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 */

package jdk.jfr;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

/**

 * Meta annotation for defining new types of event metadata.

 * <p>

 * In the following example, a transaction event is defined with two

 * user-defined annotations, {@code @Severity} and {@code @TransactionId}.

 *

 * <pre>

 * <code>

 *{@literal @}MetadataDefinition

 *{@literal @}Label("Severity")

 *{@literal @}Description("Value between 0 and 100 that indicates severity. 100 is most severe.")

 *{@literal @}Retention(RetentionPolicy.RUNTIME)

 *{@literal @}Target({ ElementType.TYPE })

 * public {@literal @}interface {@literal @}Severity {

 *   int value() default 50;

 * }

 *

 *{@literal @}MetadataDefinition

 *{@literal @}Label("Transaction Id")

 *{@literal @}Relational

 *{@literal @}Retention(RetentionPolicy.RUNTIME)

 *{@literal @}Target({ ElementType.FIELD })

 * public {@literal @}interface {@literal @}Severity {

 * }

 *

 *{@literal @}Severity(80)

 *{@literal @}Label("Transaction Blocked");

 * class TransactionBlocked extends Event {

 *  {@literal @}TransactionId

 *  {@literal @}Label("Transaction");

 *   long transactionId;

 *

 *  {@literal @}TransactionId

 *  {@literal @}Label("Transaction Blocker");

 *   long transactionId;

 * }

 *

 * </code>

 * </pre>

 *

 * Adding {@code @MetadataDefinition} to the declaration of {@code @Severity} and {@code @TransactionId}

 * ensures the information is saved by Flight Recorder.

 *

 * @since 9

 */

@Retention(RetentionPolicy.RUNTIME)

@Target({ ElementType.TYPE })

public @interface MetadataDefinition {

}