com.github.jinahya.codec.commons.DecoderProxy.java Source code

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Here is the source code for com.github.jinahya.codec.commons.DecoderProxy.java

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/*
 * Copyright 2012 Jin Kwon <jinahya at gmail.com>.
 *
 * 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.github.jinahya.codec.commons;

import java.lang.reflect.Method;

/**
 * Abstract class for proxies of {@link org.apache.commons.codec.Decoder}.
 *
 * @author Jin Kwon <jinahya at gmail.com>
 * @param <T> decoder(delegate) type parameter.
 */
public abstract class DecoderProxy<T> extends AbstractDecoderProxy<T> {

    private static final String DECODER_NAME = "org.apache.commons.codec.Decoder";

    /**
     * the class of {@link org.apache.commons.codec.Decoder}.
     */
    private static final Class<?> DECODER;

    static {
        try {
            DECODER = Class.forName(DECODER_NAME);
        } catch (final ClassNotFoundException cnfe) {
            throw new InstantiationError(cnfe.getMessage());
        }
    }

    /**
     * the method of {@code decode(Ljava/lang/Object;)Ljava/lang/Object}.
     */
    private static final Method DECODE;

    static {
        try {
            DECODE = DECODER.getMethod("decode", Object.class);
        } catch (final NoSuchMethodException nsme) {
            throw new InstantiationError(nsme.getMessage());
        }
    }

    /**
     * Creates a new proxy instance for
     * {@link org.apache.commons.codec.Decoder}.
     *
     * @param <P> proxy type parameter.
     * @param <T> decoder type parameter.
     * @param proxyType proxy type.
     * @param decoderType decoder type.
     * @param decoder decoder instance.
     *
     * @return a new proxy instance.
     */
    protected static <P extends AbstractDecoderProxy<T>, T> Object newInstance(final Class<P> proxyType,
            final Class<T> decoderType, final T decoder) {

        if (proxyType == null) {
            throw new NullPointerException("proxyType");
        }

        if (!DecoderProxy.class.isAssignableFrom(proxyType)) {
            throw new IllegalArgumentException(
                    "proxyType(" + proxyType + ") is not assignable to " + DecoderProxy.class);
        }

        return newInstance(DECODER.getClassLoader(), new Class<?>[] { DECODER }, proxyType, decoderType, decoder);
    }

    /**
     * Creates a new instance.
     *
     * @param decoder the decoder to use.
     */
    protected DecoderProxy(final T decoder) {

        super(decoder);
    }

    @Override
    public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable {

        if (DECODE.equals(method)) {
            return decode(args[0]);
        }

        throw new UnsupportedOperationException("unsupported: " + method);
    }

    /**
     * Decodes given {@code source}.
     *
     * @param source source to decode.
     *
     * @return decoded output.
     *
     * @throws Throwable if failed to decode.
     */
    protected abstract Object decode(final Object source) throws Throwable;

}