1 /*

     2  * Copyright (c) 2016, 2018, 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 jdk.jfr;

    27 

    28 import java.lang.annotation.ElementType;

    29 import java.lang.annotation.Retention;

    30 import java.lang.annotation.RetentionPolicy;

    31 import java.lang.annotation.Target;

    32 

    33 /**

    34  * Meta annotation for defining new types of event metadata.

    35  * <p>

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

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

    38  *

    39  * <pre>

    40  * <code>

    41  *{@literal @}MetadataDefinition

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

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

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

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

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

    47  *   int value() default 50;

    48  * }

    49  *

    50  *{@literal @}MetadataDefinition

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

    52  *{@literal @}Relational

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

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

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

    56  * }

    57  *

    58  *{@literal @}Severity(80)

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

    60  * class TransactionBlocked extends Event {

    61  *  {@literal @}TransactionId

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

    63  *   long transactionId;

    64  *

    65  *  {@literal @}TransactionId

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

    67  *   long transactionId;

    68  * }

    69  *

    70  * </code>

    71  * </pre>

    72  *

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

    74  * ensures the information is saved by Flight Recorder.

    75  *

    76  * @since 9

    77  */

    78 @Retention(RetentionPolicy.RUNTIME)

    79 @Target({ ElementType.TYPE })

    80 public @interface MetadataDefinition {

    81 }