dubbo-cluster/src/main/java/com/alibaba/dubbo/rpc/cluster/merger/MergerFactory.java

/*
 * Copyright 1999-2012 Alibaba Group.
 *
 *   Licensed 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.alibaba.dubbo.rpc.cluster.merger;

import com.alibaba.dubbo.common.extension.ExtensionLoader;
import com.alibaba.dubbo.common.utils.ReflectUtils;
import com.alibaba.dubbo.rpc.cluster.Merger;

import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * @author <a href="mailto:gang.lvg@alibaba-inc.com">kimi</a>
 */
public class MergerFactory {

    private static final ConcurrentMap<Class<?>, Merger<?>> mergerCache =
            new ConcurrentHashMap<Class<?>, Merger<?>>();

    public static <T> Merger<T> getMerger(Class<T> returnType) {
        Merger result;
        if (returnType.isArray()) {
            Class type = returnType.getComponentType();
            result = mergerCache.get(type);
            if (result == null) {
                loadMergers();
                result = mergerCache.get(type);
            }
            if(result == null && ! type.isPrimitive()) {
                result = ArrayMerger.INSTANCE;
            }
        } else {
            result = mergerCache.get(returnType);
            if (result == null) {
                loadMergers();
                result = mergerCache.get(returnType);
            }
        }
        return result;
    }

    static void loadMergers() {
        Set<String> names = ExtensionLoader.getExtensionLoader(Merger.class)
                .getSupportedExtensions();
        for (String name : names) {
            Merger m = ExtensionLoader.getExtensionLoader(Merger.class).getExtension(name);
            mergerCache.putIfAbsent(ReflectUtils.getGenericClass(m.getClass()), m);
        }
    }

}