ExternalConfigLoader

gistfile1.java

package com.example.app.config.logging;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

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


/**
 * Simple utility listener to load certain properties before Spring Starts up.
 * 
 * Add this entry to your web.xml:
 * <pre><listener>
    <listener-class>com.example.app.config.logging.ExternalConfigLoaderContextListener</listener-class>
  </listener></pre>
 * 
 * @author daniel
 *
 */
public class ExternalConfigLoaderContextListener implements ServletContextListener {
	private static final Logger logger = LoggerFactory.getLogger(ExternalConfigLoaderContextListener.class);

	@Override
	public void contextInitialized(ServletContextEvent sce) {
		String configLocation = sce.getServletContext().getInitParameter("CONFIGDIR");
		if(configLocation == null){
			configLocation = System.getenv("CONFIGDIR"); 
		}
		
		try{
			new LogBackConfigLoader(configLocation + "logback.xml");
		}catch(Exception e){
			logger.error("Unable to read config file", e);
		}
	}

	@Override
	public void contextDestroyed(ServletContextEvent sce) {		
	}
}

package com.example.app.config.logging;

import java.io.File;
import java.io.IOException;

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

import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.joran.JoranConfigurator;
import ch.qos.logback.core.joran.spi.JoranException;

/**
 * Simple Utility class for loading an external config file for logback
 * @author daniel
 */
public class LogBackConfigLoader {

	private Logger logger = LoggerFactory.getLogger(LogBackConfigLoader.class);
	
	public LogBackConfigLoader(String externalConfigFileLocation) throws IOException, JoranException{
		LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
		
		File externalConfigFile = new File(externalConfigFileLocation);
		if(!externalConfigFile.exists()){
			throw new IOException("Logback External Config File Parameter does not reference a file that exists");
		}else{
			if(!externalConfigFile.isFile()){
				throw new IOException("Logback External Config File Parameter exists, but does not reference a file");
			}else{
				if(!externalConfigFile.canRead()){
					throw new IOException("Logback External Config File exists and is a file, but cannot be read.");
				}else{
					JoranConfigurator configurator = new JoranConfigurator();
					configurator.setContext(lc);
					lc.reset();
					configurator.doConfigure(externalConfigFileLocation);
					
					logger.info("Configured Logback with config file from: " + externalConfigFileLocation);
				}
			}	
		}
	}
	
}


//Assumes a context.xml with the following contents:
/*<?xml version="1.0" encoding="UTF-8"?>
<Context>
	<Parameter name="CONFIGDIR" value="/usr/local/etc/exampleApp/"
		override="false" />
</Context>*/