ObjectExceptionCatcher.java

/*
 * Copyright 2016 Christoph Böhme
 *
 * 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.culturegraph.mf.flowcontrol;

import java.io.PrintWriter;
import java.io.StringWriter;

import org.culturegraph.mf.framework.FluxCommand;
import org.culturegraph.mf.framework.ObjectReceiver;
import org.culturegraph.mf.framework.annotations.Description;
import org.culturegraph.mf.framework.annotations.In;
import org.culturegraph.mf.framework.annotations.Out;
import org.culturegraph.mf.framework.helpers.DefaultObjectPipe;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * Wraps the call to the process method of the downstream module
 * in a try catch block with Exception as the catch-block's
 * argument type. This module is supposed to stop any exception
 * from downstream modules to travel further upstream. If an
 * exception is caught, a log message with log level "error" is
 * written.
 *
 * @param <T> object type
 *
 * @author Christoph Böhme
 */
@Description("passes objects through and catches exceptions.")
@In(Object.class)
@Out(Object.class)
@FluxCommand("catch-object-exception")
public final class ObjectExceptionCatcher<T> extends
		DefaultObjectPipe<T, ObjectReceiver<T>> {

	private static final Logger LOG = LoggerFactory.getLogger(ObjectExceptionCatcher.class);

	private String logPrefix;
	private boolean logStackTrace;

	public ObjectExceptionCatcher() {
		this("");
	}

	public ObjectExceptionCatcher(final String logPrefix) {
		super();
		this.logPrefix = logPrefix;
	}

	public void setLogPrefix(final String logPrefix) {
		this.logPrefix = logPrefix;
	}

	public String getLogPrefix() {
		return logPrefix;
	}

	public void setLogStackTrace(final boolean logStackTrace) {
		this.logStackTrace = logStackTrace;
	}

	public boolean isLogStackTrace() {
		return logStackTrace;
	}

	@Override
	public void process(final T obj) {
		try {
			getReceiver().process(obj);
		} catch(final Exception e) {
			LOG.error("{}'{}' while processing object: {}", logPrefix, e.getMessage(), obj);

			if (logStackTrace) {
				final StringWriter stackTraceWriter = new StringWriter();
				e.printStackTrace(new PrintWriter(stackTraceWriter));
				LOG.error("{}Stack Trace:\n{}", logPrefix, stackTraceWriter.toString());
			}
		}
	}

}