Logging JSch with Apache Commons Logging

I recently created a Java application at work which used JSch for copying files via SFTP. For the most part, JSch has worked very well for my needs. However, I ran into some problems with the way it handles timeouts, and wanted to debug JSch's behavior. I use Apache Commons Logging (usually with Log4j) in all my applications, and was a bit disappointed to discover that JSch doesn't use Commons Logging, but instead uses it's a custom com.jcraft.jsch.Logger interface. I ended writing my own simple Logger class which wraps around Apache Commons Log. This works, but has a couple of caveats due to the limitations of JSch's logging design:

• JSch uses a single instance of Logger which is shared by all JSch classes, so all messages logged by JSch classes are logged with a single class/category name.


• JSch's Logger instance is a static property of the JSch class. Therefore, you can't configure configure different Logger instances for individual JSch connections.

import com.jcraft.jsch.Logger;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Class to route log messages generated by JSch to Apache Commons Logging.
 * 
 * @author mrabbitt
 * @see com.jcraft.jsch.Logger
 */
public class JSchCommonsLogger implements Logger {
    private Log log;
    
    /**
     * Constructor with custom category name 
     * 
     * @param logName the category name used by this logger for Apache Commons.
     */
    public JSchCommonsLogger(String logName) {
        log = LogFactory.getLog(logName);
    }
    
    /**
     * Default constructor
     */
    public JSchCommonsLogger() {
        this(Logger.class.getName());
    }

    /* (non-Javadoc)
     * @see com.jcraft.jsch.Logger#isEnabled(int)
     */
    public boolean isEnabled(int level) {
        switch (level) {
        case DEBUG:
            return log.isDebugEnabled();
        case INFO:
            return log.isInfoEnabled();
        case WARN:
            return log.isWarnEnabled();
        case ERROR:
            return log.isErrorEnabled();
        case FATAL:
            return log.isFatalEnabled();
        }
        return false;
    }

    /* (non-Javadoc)
     * @see com.jcraft.jsch.Logger#log(int, java.lang.String)
     */
    public void log(int level, String message) {
        switch (level) {
        case DEBUG:
            log.debug(message);
            break;
        case INFO:
            log.info(message);
            break;
        case WARN:
            log.warn(message);
            break;
        case ERROR:
            log.error(message);
            break;
        case FATAL:
            log.fatal(message);
            break;
        }
    }

}

To use this, you'll need to do something like this somewhere in your code:

private static JSchCommonsLogger jschLogger = new JSchCommonsLogger();
com.jcraft.jsch.JSch.setLogger(jschLogger);

If you specify no argument to the JSchCommonsLogger() constructor, messages will be logged as com.jcraft.jsch. So, for example: If you're using Log4j, you can put something like this into a log4.properties to log errrors:

log4j.category.com.jcraft.jsch=ERROR