LogBox ships with a number of appenders for you to use including the File, Email, and Socket Appenders. These all have a default way that they format the data before its persisted. For instance, the FileAppender will write out each log event like so:

"Severity","Name","MM/DD/YYYY","HH:MM:SS","Category","Message"

If you need the data to be in a different format, or perhaps even change what data is included, you can do so easily without needing write your own appender. Instead, you can provide the path to a custom layout CFC in the config that will be used to format each log message. A layout component only needs to have a single method called "format()". It will receive a coldbox.system.logging.logEvent object and must return a string containing the formatted log message.

Here's an example:

screamoLayout.cfc

component {
  function format( logEvent ) {
    return UCase( logEvent.getMessage() ) & '!!!';
  }
}

And then register the layout along side the appender that will use it in the config:

logBox = {
  appenders = {
    myFile = {
      class='logbox.system.logging.appenders.FileAppender',
      layout='path.to.screamoLayout'
    }
  },
  root = { appenders='*' }
};

Now, all your application's log messages will be shouted at the top of your server's lungs. Perhaps you should check the severity and only do that if it's an error message :)

More info here: http://wiki.coldbox.org/wiki/LogBox.cfm#Creating_a_Custom_Layout

P.S. Remember, it is the responsibility of your custom layout to deserialize the extraInfo if necessary and escape any special characters in the message based on the type of storage it's going to be added to. For instance, the E-mail appender will render any HTML tags when sending the message so escape anything that's not meant to be part of the markup in the actual E-mail.