The exception telling its cannot find the class file it try to load so, there are several checks that you need to make sure they are correct.
1. The location of db.properties file, based on the "classpath:" setting look like
you put the db.properties file under "src/main" directory in your webapp path.
If you place db.properties somewhere else under "/WEB-INF/" you need to specify it exact location, otherwise, it won't find your file.
2. Make sure your "DatabaseConfiguration" is correctly configured
DatabaseConfiguration from the source:
http://commons.apache.org/configuration/apidocs/org/apache/commons/configuration/DatabaseConfiguration.html
Build a configuration from a table.-
Parameters:
datasource - the datasource to connect to the database
table - the name of the table containing the configurations
keyColumn - the column containing the keys of the configuration
valueColumn - the column containing the values of the configuration
3. Make sure your db.properties file properly configured
For example,
Make sure your port and the setting is correct relative to your application and configuration.
4. Maybe something else not right if all above suggestion is met.