core/src/main/java/org/apache/commons/proxy2/DefaultProxyFactory.java

/*
 * 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 org.apache.commons.proxy2;

import java.util.Arrays;
import java.util.ServiceLoader;

/**
 * {@link ProxyFactory} implementation that delegates to the first discovered {@link ProxyFactory} service provider that
 * {@link #canProxy(Class...)}.
 */
class DefaultProxyFactory implements ProxyFactory
{
    /** Shared instance */
    static final DefaultProxyFactory INSTANCE = new DefaultProxyFactory();

    private static final ServiceLoader<ProxyFactory> SERVICES = ServiceLoader.load(ProxyFactory.class);

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean canProxy(Class<?>... proxyClasses)
    {
        for (ProxyFactory proxyFactory : SERVICES)
        {
            if (proxyFactory.canProxy(proxyClasses))
            {
                return true;
            }
        }
        return false;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public <T> T createDelegatorProxy(ObjectProvider<?> delegateProvider, Class<?>... proxyClasses)
    {
        @SuppressWarnings("unchecked") // type inference
        final T result = (T) getCapableProxyFactory(proxyClasses).createDelegatorProxy(delegateProvider, proxyClasses);
        return result;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public <T> T createDelegatorProxy(ClassLoader classLoader, ObjectProvider<?> delegateProvider,
            Class<?>... proxyClasses)
    {
        @SuppressWarnings("unchecked") // type inference
        final T result = (T) getCapableProxyFactory(proxyClasses).createDelegatorProxy(classLoader, delegateProvider,
                proxyClasses);
        return result;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public <T> T createInterceptorProxy(Object target, Interceptor interceptor, Class<?>... proxyClasses)
    {
        @SuppressWarnings("unchecked") // type inference
        final T result = (T) getCapableProxyFactory(proxyClasses).createInterceptorProxy(target, interceptor,
                proxyClasses);
        return result;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public <T> T createInterceptorProxy(ClassLoader classLoader, Object target, Interceptor interceptor,
            Class<?>... proxyClasses)
    {
        @SuppressWarnings("unchecked") // type inference
        final T result = (T) getCapableProxyFactory(proxyClasses).createInterceptorProxy(classLoader, target,
                interceptor, proxyClasses);
        return result;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public <T> T createInvokerProxy(Invoker invoker, Class<?>... proxyClasses)
    {
        @SuppressWarnings("unchecked") // type inference
        final T result = (T) getCapableProxyFactory(proxyClasses).createInvokerProxy(invoker, proxyClasses);
        return result;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public <T> T createInvokerProxy(ClassLoader classLoader, Invoker invoker, Class<?>... proxyClasses)
    {
        @SuppressWarnings("unchecked") // type inference
        final T result = (T) getCapableProxyFactory(proxyClasses)
                .createInvokerProxy(classLoader, invoker, proxyClasses);
        return result;
    }

    private ProxyFactory getCapableProxyFactory(Class<?>... proxyClasses)
    {
        for (ProxyFactory proxyFactory : SERVICES)
        {
            if (proxyFactory.canProxy(proxyClasses))
            {
                return proxyFactory;
            }
        }
        throw new IllegalArgumentException("Could not proxy " + Arrays.toString(proxyClasses));
    }
}