com.davidbracewell.reflection.BeanDescriptorCache.java Source code

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Here is the source code for com.davidbracewell.reflection.BeanDescriptorCache.java

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/*
 * (c) 2005 David B. Bracewell
 *
 * 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.
 */

package com.davidbracewell.reflection;

import com.davidbracewell.config.Config;
import com.google.common.base.Throwables;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

import java.util.concurrent.ExecutionException;

/**
 * A cache of {@link BeanDescriptor} to speed up performance of using {@link BeanMap}s. The cache specification be set
 * using <code>com.davidbracewell.reflection.BeanDescriptorCache.spec</code> and follows the {@link com.google.common.cache.LoadingCache} spec
 * format found in
 * <a href= "http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/cache/CacheBuilder.html" >the
 * Guava documentation.By defaul it set to
 * <p/>
 * <pre>
 * maximumSize=100,expireAfterWrite=10m
 * </pre>
 * <p/>
 * </a>
 *
 * @author David B. Bracewell
 */
public class BeanDescriptorCache {

    private static volatile BeanDescriptorCache INSTANCE = null;

    private final LoadingCache<Class<?>, BeanDescriptor> cache;

    /**
     * @return An instance of the {@link BeanDescriptorCache}.
     */
    public static BeanDescriptorCache getInstance() {
        if (INSTANCE == null) {
            synchronized (BeanDescriptorCache.class) {
                if (INSTANCE == null) {
                    INSTANCE = new BeanDescriptorCache();
                }
            }
        }
        return INSTANCE;
    }

    protected BeanDescriptorCache() {
        String spec = Config.get(BeanDescriptorCache.class, "spec")
                .asString("maximumSize=100,expireAfterWrite=10m");
        cache = CacheBuilder.from(spec).build(new CacheLoader<Class<?>, BeanDescriptor>() {
            public BeanDescriptor load(Class<?> key) {
                return new BeanDescriptor(key);
            }
        });
    }

    /**
     * Gets a {@link BeanDescriptor} for a <code>Class</code>
     *
     * @param clazz The class for which a {@link BeanDescriptor} is to be created.
     * @return A {@link BeanDescriptor} for the given class
     */
    public synchronized BeanDescriptor get(Class<?> clazz) {
        try {
            return cache.get(clazz);
        } catch (ExecutionException e) {
            throw Throwables.propagate(e);
        }
    }

}// END OF CLASS BeanDescriptorCache