001/* 002* CDDL HEADER START 003 * 004 * The contents of this file are subject to the terms of the 005 * Common Development and Distribution License, Version 1.0 only 006 * (the "License"). You may not use this file except in compliance 007 * with the License. 008 * 009 * You can obtain a copy of the license at legal-notices/CDDLv1_0.txt 010 * or http://forgerock.org/license/CDDLv1.0.html. 011 * See the License for the specific language governing permissions 012 * and limitations under the License. 013 * 014 * When distributing Covered Code, include this CDDL HEADER in each 015 * file and include the License file at legal-notices/CDDLv1_0.txt. 016 * If applicable, add the following below this CDDL HEADER, with the 017 * fields enclosed by brackets "[]" replaced with your own identifying 018 * information: 019 * Portions Copyright [yyyy] [name of copyright owner] 020 * 021 * CDDL HEADER END 022 * 023 * 024 * Copyright 2010 Sun Microsystems, Inc. 025 * Portions copyright 2013 ForgeRock AS. 026 */ 027 028package org.forgerock.opendj.server.core; 029 030/** 031 * Class used to define dynamic typed attachments on {@link AttachmentHolder} 032 * instances. Storing attachment values in {@link AttachmentHolder} has the 033 * advantage of the <tt>Attachment</tt> value being typed when compared to Map 034 * storage: 035 * 036 * @param <T> 037 * The type of attachment. 038 */ 039public final class Attachment<T> { 040 private final T defaultValue; 041 private final String name; 042 043 /** 044 * Construct a new attachment with the specified name and default value. 045 * 046 * @param name 047 * Attachment name. 048 * @param defaultValue 049 * Attachment default value, which will be used, if it is not 050 * set. 051 */ 052 public Attachment(final String name, final T defaultValue) { 053 this.name = name; 054 this.defaultValue = defaultValue; 055 } 056 057 /** 058 * Retrieves the attachment value, stored on the {@link AttachmentHolder}. 059 * 060 * @param attachmentHolder 061 * {@link AttachmentHolder}. 062 * @return attachment value. 063 */ 064 public T get(final AttachmentHolder attachmentHolder) { 065 T value = get0(attachmentHolder); 066 if (value == null) { 067 value = defaultValue; 068 } 069 return value; 070 } 071 072 /** 073 * Remove attachment value, stored on the {@link AttachmentHolder}. 074 * 075 * @param attachmentHolder 076 * {@link AttachmentHolder}. 077 * @return The former value or {@code null} if there was previously no 078 * value. 079 */ 080 public T remove(final AttachmentHolder attachmentHolder) { 081 final T value = get0(attachmentHolder); 082 if (value != null) { 083 set(attachmentHolder, null); 084 } 085 return value; 086 } 087 088 /** 089 * Set attachment value, stored on the {@link AttachmentHolder}. If a value 090 * already exists, it will be replaced. 091 * 092 * @param attachmentHolder 093 * {@link AttachmentHolder}. 094 * @param value 095 * attachment value to set. 096 * @return The former value or {@code null} if there was previously no 097 * value. 098 */ 099 public T set(final AttachmentHolder attachmentHolder, final T value) { 100 final T oldValue = get0(attachmentHolder); 101 attachmentHolder.setAttachment(name, value); 102 return oldValue; 103 } 104 105 @SuppressWarnings("unchecked") 106 private T get0(final AttachmentHolder attachmentHolder) { 107 return (T) attachmentHolder.getAttachment(name); 108 } 109}