1/* 2 * Copyright (c) 2015, 2017, 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 26package javax.accessibility; 27 28/** 29 * Service Provider Interface (SPI) for Assistive Technology. 30 * <p> 31 * This service provider class provides mappings from the platform specific 32 * accessibility APIs to the Java Accessibility API. 33 * <p> 34 * Each service provider implementation is named and can be activated via the 35 * {@link #activate} method. Service providers can be loaded when the default 36 * {@link java.awt.Toolkit toolkit} is initialized. 37 * 38 * @apiNote There will typically be one provider per platform, such as Windows 39 * or Linux, to support accessibility for screen readers and 40 * magnifiers. However, more than one service provider can be 41 * activated. For example, a test tool which provides visual results 42 * obtained by interrogating the Java Accessibility API can be 43 * activated along with the activation of the support for screen 44 * readers and screen magnifiers. 45 * @see java.awt.Toolkit#getDefaultToolkit 46 * @see java.util.ServiceLoader 47 * @since 9 48 */ 49public abstract class AccessibilityProvider { 50 51 /** 52 * Initializes a new accessibility provider. 53 * 54 * @throws SecurityException If a security manager has been installed and it 55 * denies {@link RuntimePermission} {@code "accessibilityProvider"} 56 */ 57 protected AccessibilityProvider() { 58 // Use a permission check when calling a private constructor to check 59 // that the proper security permission has been granted before the 60 // {@code Object} superclass is called. If an exception is thrown before 61 // the {@code Object} superclass is constructed a finalizer in a 62 // subclass of this class will not be run. This protects against a 63 // finalizer vulnerability. 64 this(checkPermission()); 65 } 66 67 /** 68 * Allows to check a permission before the {@code Object} is called. 69 * 70 * @param ignore unused stub to call a {@link #checkPermission()}} 71 */ 72 private AccessibilityProvider(Void ignore) { } 73 74 /** 75 * If this code is running with a security manager and if the permission 76 * {@code "accessibilityProvider"} has not been granted 77 * {@code SecurityException} will be thrown. 78 * 79 * @return {@code null} if {@code SecurityException} was not thrown 80 * @throws SecurityException If a security manager has been installed and it 81 * denies {@link RuntimePermission} {@code "accessibilityProvider"} 82 */ 83 private static Void checkPermission() { 84 SecurityManager sm = System.getSecurityManager(); 85 if (sm != null) 86 sm.checkPermission(new RuntimePermission("accessibilityProvider")); 87 return null; 88 } 89 90 /** 91 * Returns the name of this service provider. This name is used to locate a 92 * requested service provider. 93 * 94 * @return the name of this service provider 95 */ 96 public abstract String getName(); 97 98 /** 99 * Activates the support provided by this service provider. 100 */ 101 public abstract void activate(); 102} 103