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.Inherited; 30 import java.lang.annotation.Retention; 31 import java.lang.annotation.RetentionPolicy; 32 import java.lang.annotation.Target; 33 34 /** 35 * Event annotation, to associate the event type with a category, in the format 36 * of a human-readable path. 37 * <p> 38 * The category determines how an event is presented to the user. Events that 39 * are in the same category are typically displayed together in graphs and 40 * trees. To avoid the overlap of durational events in graphical 41 * representations, overlapping events must be in separate categories. 42 * <p> 43 * For example, to monitor image uploads to a web server with a separate thread 44 * for each upload, an event called File Upload starts when the user uploads a 45 * file and ends when the upload is complete. For advanced diagnostics about 46 * image uploads, more detailed events are created (for example, Image Read, 47 * Image Resize, and Image Write). During these detailed events. other low 48 * level-events could occur (for example, Socket Read and File Write). 49 * <p> 50 * The following example shows a visualization that avoids overlaps: 51 * 52 * <pre> 53 * ------------------------------------------------------------------- 54 * | File Upload | 55 * ------------------------------------------------------------------ 56 * | Image Read | Image Resize | Image Write | 57 * ------------------------------------------------------------------ 58 * | Socket Read | Socket Read | | File Write | 59 * ------------------------------------------------------------------- 60 * </pre> 61 * 62 * The example can be achieved by using the following categories: 63 * 64 * <table class="striped"> 65 * <caption>Recording options and their purpose.</caption> <thead> 66 * <tr> 67 * <th scope="col">Event Name</th> 68 * <th scope="col">Annotation</th> 69 * </tr> 70 * </thead> <tbody> 71 * <tr> 72 * <th scope="row">File Upload</th> 73 * <td><code>@Category("Upload")</code></td> 74 * </tr> 75 * <tr> 76 * <th scope="row">Image Read</th> 77 * <td><code>@Category({"Upload", "Image Upload"})</code></td> 78 * </tr> 79 * <tr> 80 * <th scope="row">Image Resize</th> 81 * <td><code>@Category({"Upload", "Image Upload"})</code></td> 82 * </tr> 83 * <tr> 84 * <th scope="row">Image Write</th> 85 * <td><code>@Category({"Upload", "Image Upload"})</code></td> 86 * </tr> 87 * <tr> 88 * <th scope="row">Socket Read</th> 89 * <td><code>@Category("Java Application")</code></td> 90 * </tr> 91 * <tr> 92 * <th scope="row">File Write</th> 93 * <td><code>@Category("Java Application")</code></td> 94 * </tr> 95 * </tbody> 96 * </table> 97 * <p> 98 * The File Upload, Image Read, and Socket Read events happen concurrently (in 99 * the same thread), but the events are in different categories so they do not 100 * overlap in the visualization. 101 * <p> 102 * The following examples shows how the category is used to determine how events 103 * are visualized in a tree: 104 * 105 * <pre> 106 * |- Java Application 107 * | |- Socket Read 108 * | |- File Write 109 * |- Upload 110 * |- File Upload 111 * |- Image Upload 112 * |- Image Read 113 * |- Image Resize 114 * |- File Write 115 * </pre> 116 * 117 * @since 9 118 */ 119 @MetadataDefinition 120 @Target({ ElementType.TYPE }) 121 @Inherited 122 @Retention(RetentionPolicy.RUNTIME) 123 public @interface Category { 124 /** 125 * Returns the category names for this annotation, starting with the root. 126 * 127 * @return the category names 128 */ value()129 String[] value(); 130 } 131