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 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
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 * 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 javax.accessibility;

/**
 * Service Provider Interface (SPI) for Assistive Technology.
 * <p>
 * This service provider class provides mappings from the platform
 * specific accessibility APIs to the Java Accessibility API.
 * <p>
 * Each service provider implementation is named and can be activated via the
 * {@link #activate} method. Service providers can be loaded when the default
 * {@link java.awt.Toolkit toolkit} is initialized.
 *
 * @apiNote There will typically be one provider per platform, such as Windows
 * or Linux, to support accessibility for screen readers and magnifiers.  However,
 * more than one service provider can be activated.  For example, a test tool
 * which provides visual results obtained by interrogating the Java Accessibility
 * API can be activated along with the activation of the support for screen readers
 * and screen magnifiers.
 *
 * @see java.awt.Toolkit#getDefaultToolkit
 * @see java.util.ServiceLoader
 * @since 9
 */
public abstract class AccessibilityProvider {

    /**
     * Initializes a new accessibility provider.
     *
     * @throws  SecurityException
     *          If a security manager has been installed and it denies
     *          {@link RuntimePermission} {@code "accessibilityProvider"}
     */
    protected AccessibilityProvider() {
        // Use a permission check when calling a private constructor to check that
        // the proper security permission has been granted before the Object superclass
        // is called.  If an exception is thrown before the Object superclass is
        // constructed a finalizer in a subclass of this class will not be run.
        // This protects against a finalizer vulnerability.
        this(checkPermission());
    }

    private AccessibilityProvider(Void ignore) { }

    /**
     * If this code is running with a security manager and if the permission
     * "accessibilityProvider" has not been granted SecurityException will be thrown.
     *
     */
    private static Void checkPermission() {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null)
            sm.checkPermission(new RuntimePermission("accessibilityProvider"));
        return null;
    }

    /**
     * Returns the name of this service provider.  This name is used to locate a
     * requested service provider.
     *
     * @return the name of this service provider
     */
    public abstract String getName();

    /**
     * Activates the support provided by this service provider.
     */
    public abstract void activate();

}