The Log4E logging plug-in

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The Log4E logging plug-in

• David Gallardo

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What is logging good for?

• Tracing program execution during development
• Debugging
• Providing an audit trail for a program
• Recording soft-errors (lost connections, etc.)
  for monitoring performance and troubleshooting
• A logging framework lets you use different
  logging levels
• You can turn different types of messages on and
  off
• You can send different types of messages to
  different destinations

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Adding logging code

• Replaces System.out.println() calls throughout
• Dont need to be removed
• Like adding System.out.println() calls, its
  somewhat tedious to add logging code
• Utility of logging code is improved if its
  consistentlogs can be searched with scripts, for
  example

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The Log4E plug-in

• Provides wizards that automate the addition of
  logging code
• Add import and declaration for logger
• Insert logging at start and end of methods
• Insert logging of variables and method parameters

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What Log4E doesnt do

• Log4E does not provide a logging framework
• Doesnt configure your framework
• Doesnt make a fresh pot of coffee

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Choosing a logging framework

• Log4E supports three logging frameworks
• Log4J
• Java 1.4 Logging
• Jakarta Commons Logging
• Log4J is the original logging framework that Java
  1.4 logging is modeled after
• Jakarta Commons Logging is actually a wrapper for
  logging frameworks
• Well use Log4J in this example because its
  mature, well-documented and supported, and easier
  to configure

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Installing Log4J

• Download a zip or compressed tarfile from
  Apache.org website
• Uncompress to a local directory
• In your Eclipse projects properties
• Locate Java Build Path
• On Libraries page, click on Add External Jars
• Browse for your Log4J directory, and locate the
  log4J Jar file in the /dist/lib directory
• Press Open, followed by OK

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Create a Log4J configuration file

• The easiest way to configure Log4J is to add a
  log4j.properties file to your source directory.
• There are many options available which we wont
  cover here, but essentially you need to define
• A logger
• An appender
• A pattern layout
• The following example uses the default root
  logger, appends to the console and prints the
  date, time, message priority, thread and message

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A sample log4j.properties file

• Logger
• log4j.rootLoggerDEBUG, ConApp
• Appender
• log4j.appender.ConApporg.apache.log4j.ConsoleAppe
  nder
• PatternLayout
• log4j.appender.ConApp.layoutorg.apache.log4j.Patt
  ernLayout
• log4j.appender.ConApp.layout.ConversionPatternd
  t -5p c - mn

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Demo

• Create a simple Java application
• Ensure log4j is on class path
• Use Log4E to add several types of logging
  messages
• Run program