TraceInterceptor.java

/*
 * Modified by mmatthies.
 *
 * Copyright 2011 the original author or authors.
 *
 * 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 ch.nydi.aop.interceptor;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.apache.commons.lang.ArrayUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Logs the the arguments and the return value of a method invocation.
 *
 * @author Daniel Nydegger
 */
public class TraceInterceptor extends AbstractInterceptor implements MethodInterceptor {

	private final Logger logger = LoggerFactory.getLogger(TraceInterceptor.class);

	@Override
	public Object invoke(MethodInvocation invocation)
			throws Throwable {

		final String prefix = "invocation arguments of " + invocation.getMethod().getName() + " ";

		final Object[] arguments = invocation.getArguments();
		if (ArrayUtils.isEmpty(arguments)) {
			this.logger.trace(prefix + "{no arguments}");
		} else {
			final StringBuilder flattenArguments = new StringBuilder();
			flattenArguments.append("{");
			for (int i = 0; i < arguments.length; i++) {
				if (i > 0) {
					flattenArguments.append(" | ");
				}
				flattenArguments.append(TraceInterceptor.this.flattenArgument(arguments[i]));
			}
			flattenArguments.append("}");
			this.logger.trace(prefix + flattenArguments.toString());
		}

		Object invocationResult = null;

		try {
			invocationResult = invocation.proceed();
		} catch (final Throwable e) {
			this.logger.trace("execption occured, no return value");
			throw e;
		}
		finally {
			final StringBuilder builder = new StringBuilder();
			builder.append("invocation return value of ").append(invocation.getMethod().getName()).append(": {").append(
					this.flattenArgument(invocationResult)).append("}");
			this.logger.trace(builder.toString());
		}

		return invocationResult;
	}
}