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'databene commons' is an open source Java library by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * All rights reserved.
 *
 * 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 org.databene.commons.log;

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

import org.databene.commons.ArrayFormat;
import org.databene.commons.BeanUtil;
import org.databene.commons.Level;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Creates a proxy to a class which logs all invocations of parent interface methods.
 * Created at 17.09.2009 10:54:08
 * @since 0.5.0
 * @author Volker Bergmann
 */

public class LoggingProxyFactory {
	
	private LoggingProxyFactory() {}

    public static  T createProxy(Class interfaceClass, T realObject) {
		return createProxy(interfaceClass, realObject, Level.debug);
	}
	
    public static  T createProxy(Class interfaceClass, T realObject, Level level) {
		return createProxy(interfaceClass, realObject, level, BeanUtil.getContextClassLoader());
	}
	
    @SuppressWarnings("unchecked")
    public static  T createProxy(Class interfaceClass, T realObject, Level level, ClassLoader classLoader) {
		LoggingInvocationHandler handler = new LoggingInvocationHandler(realObject, level);
		return (T) Proxy.newProxyInstance(classLoader, new Class[] { interfaceClass }, handler);
	}
	
	protected static class LoggingInvocationHandler implements InvocationHandler {
		
		private Object realObject;
		private Logger logger;
		private Level level;
		
        public LoggingInvocationHandler(Object realObject, Level level) {
        	this.realObject = realObject;
        	this.logger = LoggerFactory.getLogger(realObject.getClass());
        	this.level = level;
        }

		@Override
		public Object invoke(Object object, Method method, Object[] args) throws Throwable {
			String message = method.getName() + '(' + ArrayFormat.format(args) + ')';
			switch (level) {
				case ignore: break;
				case trace: logger.trace(message); break;
				case debug: logger.debug(message); break;
				case info:  logger.info(message);  break;
				case warn:  logger.warn(message);  break;
				case error: logger.error(message); break;
				case fatal: logger.error(message); break;
			}
	        return BeanUtil.invoke(realObject, method, args);
        }

	}
	
}