Using custom StreamProcessors with Embedmongo / How to redirect mongo output to SLF4J

EmbeddedMongo.java

import java.io.IOException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.mongodb.Mongo;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;

import de.flapdoodle.embedmongo.MongoDBRuntime;
import de.flapdoodle.embedmongo.MongodExecutable;
import de.flapdoodle.embedmongo.config.MongodConfig;
import de.flapdoodle.embedmongo.config.MongodProcessOutputConfig;
import de.flapdoodle.embedmongo.config.RuntimeConfig;
import de.flapdoodle.embedmongo.distribution.Version;
import de.flapdoodle.embedmongo.io.IStreamProcessor;
import de.flapdoodle.embedmongo.io.NamedOutputStreamProcessor;
import de.flapdoodle.embedmongo.io.StreamToLineProcessor;
import de.flapdoodle.embedmongo.runtime.Network;

/**
 * Special subclass of {@link Mongo} that
 * launches an embedded Mongod server instance in a separate process.
 * 
 * @author Alexandre Dutra
 */
public class EmbeddedMongo extends Mongo {

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

	public static final String DEFAULT_HOST = "127.0.0.1";

	public static final int DEFAULT_PORT = 27017;

	public static final WriteConcern DEFAULT_WRITE_CONCERN = WriteConcern.FSYNC_SAFE;
	
	public static final Version DEFAULT_VERSION = Version.V2_0;

	public EmbeddedMongo() throws MongoException, IOException {
		this(DEFAULT_HOST, DEFAULT_PORT);
	}

	public EmbeddedMongo(int port) throws MongoException, IOException {
		this(DEFAULT_HOST, port);
	}

	public EmbeddedMongo(String host, int port) throws MongoException, IOException {
		this(host, port, DEFAULT_WRITE_CONCERN);
	}

	public EmbeddedMongo(String host, int port, WriteConcern writeConcern) throws MongoException, IOException {
		this(host, port, writeConcern, DEFAULT_VERSION);
	}
	
	public EmbeddedMongo(String host, int port, WriteConcern writeConcern, Version version) throws MongoException, IOException {
		super(host, port);
		this.setWriteConcern(writeConcern);
		RuntimeConfig runtimeConfig = new RuntimeConfig();
		IStreamProcessor mongodOutput =
				new NamedOutputStreamProcessor("[mongod out]",
						new StreamToLineProcessor(
								new Slf4jStreamProcessor(LOG, Slf4jLevel.INFO)));
		IStreamProcessor mongodError =
				new NamedOutputStreamProcessor("[mongod err]",
						new StreamToLineProcessor(
								new Slf4jStreamProcessor(LOG, Slf4jLevel.WARN)));
		IStreamProcessor commandsOutput =
				new NamedOutputStreamProcessor("[mongod kill]",
						new StreamToLineProcessor(
								new Slf4jStreamProcessor(LOG, Slf4jLevel.INFO)));
		runtimeConfig.setMongodOutputConfig(new MongodProcessOutputConfig(mongodOutput, mongodError, commandsOutput));
		MongoDBRuntime runtime = MongoDBRuntime.getInstance(runtimeConfig);
		MongodExecutable mongodExe = runtime.prepare(new MongodConfig(version, port, Network.localhostIsIPv6()));
		mongodExe.start();
	}
}

Slf4jLevel.java

import org.slf4j.Logger;

public enum Slf4jLevel {
	
	TRACE {
		@Override
		public void log(Logger logger, String message) {
			logger.trace(message);
		}
	},
	
	DEBUG {
		@Override
		public void log(Logger logger, String message) {
			logger.debug(message);
		}
	},
	
	INFO {
		@Override
		public void log(Logger logger, String message) {
			logger.info(message);
		}
	},
	
	WARN {
		@Override
		public void log(Logger logger, String message) {
			logger.warn(message);
		}
	},
	
	ERROR {
		@Override
		public void log(Logger logger, String message) {
			logger.error(message);
		}
	}

	;

	public abstract void log(Logger logger, String message);
}

Slf4jStreamProcessor.java

import org.slf4j.Logger;

import de.flapdoodle.embedmongo.io.IStreamProcessor;
import de.flapdoodle.embedmongo.io.StreamToLineProcessor;

/**
 * {@link IStreamProcessor} using SLF4J to log messages.
 * Should be preferably wrapped within a {@link StreamToLineProcessor}
 * for a better output.
 * 
 * The constructor takes a {@link Logger} that will be used to log messages,
 * and an instance of {@link Slf4jLevel} to determine which method to call
 * on the {@link Logger} instance.
 * 
 * Example of usage:
 * 
 * <pre>
 * Logger logger = ...
 * IStreamProcessor mongodOutput =
 *   new NamedOutputStreamProcessor("[mongod out]",
 *     new StreamToLineProcessor(
 *         new Slf4jStreamProcessor(logger, Slf4jLevel.INFO)));
 * </pre>
 * 
 * @author Alexandre Dutra
 */
public class Slf4jStreamProcessor implements IStreamProcessor {

	private final Logger logger;

	private final Slf4jLevel level;

	public Slf4jStreamProcessor(Logger logger, Slf4jLevel level) {
		this.logger = logger;
		this.level = level;
	}

	@Override
	public void process(String line) {
		level.log(logger, stripLineEndings(line));
	}

	@Override
	public void onProcessed() {
	}

	protected String stripLineEndings(String line) {
		//we still need to remove line endings that are passed on by StreamToLineProcessor...
		return line.replaceAll("[\n\r]+", "");
	}

}