IIORegistry.java example

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appengine-export-master
/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
/**
 * @author Rustem V. Rafikov
 */
package com.google.code.appengine.imageio.spi;

import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Arrays;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.Map;


import org.apache.harmony.x.imageio.plugins.gif.GIFImageReaderSpi;
import org.apache.harmony.x.imageio.plugins.jpeg.JPEGImageReaderSpi;
import org.apache.harmony.x.imageio.plugins.jpeg.JPEGImageWriterSpi;
import org.apache.harmony.x.imageio.plugins.png.PNGImageReaderSpi;
import org.apache.harmony.x.imageio.plugins.png.PNGImageWriterSpi;
import org.apache.harmony.x.imageio.spi.FileIISSpi;
import org.apache.harmony.x.imageio.spi.FileIOSSpi;
import org.apache.harmony.x.imageio.spi.InputStreamIISSpi;
import org.apache.harmony.x.imageio.spi.OutputStreamIOSSpi;
import org.apache.harmony.x.imageio.spi.RAFIISSpi;
import org.apache.harmony.x.imageio.spi.RAFIOSSpi;

import com.google.code.appengine.imageio.spi.IIORegistry;
import com.google.code.appengine.imageio.spi.ServiceRegistry;

public final class IIORegistry extends ServiceRegistry {

    private static Map<ThreadGroup, IIORegistry> instances = 
    	Collections.synchronizedMap(new IdentityHashMap<ThreadGroup, IIORegistry>());

    private static final Class[] CATEGORIES = new Class[] {
                    com.google.code.appengine.imageio.spi.ImageWriterSpi.class,
                    com.google.code.appengine.imageio.spi.ImageReaderSpi.class,
                    com.google.code.appengine.imageio.spi.ImageInputStreamSpi.class,
                    // javax.imageio.spi.ImageTranscoderSpi.class,
                    com.google.code.appengine.imageio.spi.ImageOutputStreamSpi.class };

    private IIORegistry() {
        super(Arrays.<Class<?>> asList(CATEGORIES).iterator());
        registerBuiltinSpis();
        registerApplicationClasspathSpis();
    }

    private void registerBuiltinSpis() {
        registerServiceProvider(new JPEGImageWriterSpi());
        registerServiceProvider(new JPEGImageReaderSpi());
        registerServiceProvider(new PNGImageReaderSpi());
        registerServiceProvider(new PNGImageWriterSpi());
        registerServiceProvider(new GIFImageReaderSpi());
        registerServiceProvider(new FileIOSSpi());
        registerServiceProvider(new FileIISSpi());
        registerServiceProvider(new RAFIOSSpi());
        registerServiceProvider(new RAFIISSpi());
        registerServiceProvider(new OutputStreamIOSSpi());
        registerServiceProvider(new InputStreamIISSpi());
    }

    public static IIORegistry getDefaultInstance() {
        ThreadGroup tg = Thread.currentThread().getThreadGroup();
        synchronized (instances) {
        	IIORegistry instance = instances.get(tg);
        	if (instance == null) {
        		synchronized(IIORegistry.class) {
        			instance = new IIORegistry();
        		}
            	instances.put(tg, instance);
        	}
        	return instance;
        }    
    }

    @SuppressWarnings("unchecked")
	public void registerApplicationClasspathSpis() {
        AccessController.doPrivileged(new PrivilegedAction() {
			public Object run() {
				Iterator<Class<?>> categories = getCategories();
				while (categories.hasNext()) {
					Iterator providers = lookupProviders(categories.next());
					registerServiceProviders(providers);
				}
				return this;
			}
        });
    }
}