Spring property loader from the datasource.

gistfile1.java

import java.io.ByteArrayInputStream;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

import javax.naming.NamingException;
import javax.sql.DataSource;

import org.apache.commons.lang.exception.ExceptionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.ResultSetExtractor;
import org.springframework.jndi.JndiTemplate;

public class RewritablePropertiesConfigurer extends PropertyPlaceholderConfigurer
{
	private final static Logger				log	= LoggerFactory.getLogger(RewritablePropertiesConfigurer.class);
	private String databaseKey = "epd.jndi.database";
	
	private final  String query = "select props from settings"; 
	
	private JndiTemplate jndiTemplate = new JndiTemplate();
	
	@Override
	protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props) throws BeansException
	{
		log.debug("Start redefining properties");
		Properties dbProps = getSettings(props);
		log.debug("Loaded settings {}", dbProps);
		props.putAll(dbProps);
		log.debug("Props adjusted {}", props);
		super.processProperties(beanFactoryToProcess, props);
	}
	
	private DataSource getDataSource(String jndiKey){
		DataSource ds = null;
		try {
			ds= jndiTemplate.lookup(jndiKey, DataSource.class);
		} catch (NamingException e) {
			log.error(ExceptionUtils.getFullStackTrace(e));
			throw new RuntimeException(e);
		}
		return ds;
		
	}
	
	private Properties getSettings(Properties props){
		 String dsKey = props.getProperty(databaseKey);
		 DataSource ds =  getDataSource(dsKey);
		 JdbcTemplate jdbcTemplate = new JdbcTemplate(ds);
		 String holderList = jdbcTemplate.query(query, new ResultSetExtractor<String>(){
			@Override
			public String extractData(ResultSet rs) throws SQLException,
					DataAccessException {
				if (rs.next()){
					return rs.getString("epd_props");					
				}
				else{
					throw new RuntimeException("Failed to load properties from database");
				}
			}
		 });
		 Properties dbProps = new Properties();
		 try {
			dbProps.load(new ByteArrayInputStream(holderList.getBytes("UTF-8")));
		} catch (Exception e) {
			log.error(ExceptionUtils.getFullStackTrace(e));
			throw new RuntimeException(e);
		}
		 return dbProps;
	}
	
}