User Guide

About loggers, handlers, and filters 45
About loggers, handlers, and filters
Loggers
Loggers are used for maintaining and debugging applications. Developers embed various types of trace messages
in the code at critical points. These trace messages are logged in appropriate files on the client side or server side
as per the settings, helping your maintenance engineers trace the cause of the problem.
The logger can log messages:
 On the console
 In a text file on the local machine
 In text and XML format on a remote machine
You can allot different levels of severity to messages. These severity levels are called trace levels. The display of
messages can be filtered using these trace levels.
Messages can also be filtered based on the source of the log.
Loggers help you to keep track of the system's efficiency. You can use system logs as well as any additional logs
that you might create to check for bugs, real time errors, or application performances.
Handlers
Handlers process the event data generated by the loggers. Handlers correspond to a physical device, such as a
console or file. They usually format the data. At least one handler must be attached to a logger or the event data
is lost.
The different types of handlers that can be attached to a logger are:
 Console Handler: Logs the data in a Web logic console.
 File Handler: Logs the data in a specified file.
Filters
Filters control the log records that are written to the output devices controlled by Handlers. Each Logger can
have a filter associated with it. Filters help sort the criteria by which logger can display only the information that
is asked for.
Managing handlers
Creating handlers
You can create and manage handlers only from the shared resources. Handlers help you process the data
generated by loggers in a usable format.