commons-jcs-jcache/src/main/java/org/apache/commons/jcs/jcache/proxy/ExceptionWrapperHandler.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.jcs.jcache.proxy;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class ExceptionWrapperHandler<T> implements InvocationHandler
{
    private final T delegate;
    private final Constructor<? extends RuntimeException> wrapper;

    public ExceptionWrapperHandler(final T delegate, final Class<? extends RuntimeException> exceptionType)
    {
        this.delegate = delegate;
        try
        {
            this.wrapper = exceptionType.getConstructor(Throwable.class);
        }
        catch (final NoSuchMethodException e)
        {
            throw new IllegalStateException(e);
        }
    }

    @Override
    public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable
    {
        try
        {
            return method.invoke(delegate, args);
        }
        catch (final InvocationTargetException ite)
        {
            final Throwable e = ite.getCause();
            if (RuntimeException.class.isInstance(e))
            {
                final RuntimeException re;
                try
                {
                    re = wrapper.newInstance(e);
                }
                catch (final Exception e1)
                {
                    throw new IllegalArgumentException(e1);
                }
                throw re;
            }
            throw e;
        }
    }

    public static <T> T newProxy(final ClassLoader loader, final T delegate, final Class<? extends RuntimeException> exceptionType,
            final Class<T> apis)
    {
        return (T) Proxy.newProxyInstance(loader, new Class<?>[] { apis }, new ExceptionWrapperHandler<T>(delegate, exceptionType));
    }
}