Java logging
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The document discusses various Java logging frameworks and the complexities involved in their configuration and usage. It highlights the need for effective logging during both development and production for error identification and troubleshooting. The document also outlines key logging entities, their interactions, and presents a conceptual model for understanding these frameworks.
Java logging
- 1. Java Logging Frameworks Demystified By Jumping Bean 21 May 2012
- 2. Who Am I? Mark Clarke – Java Developer Working for Jumping Bean, an open source solutions integration company Working with Java & open source technologies since 2001 Co-founder of Jozi JUG
- 3. Jozi JUG
- 4. Jozi JUG Meet once a month in Johannesburg, Talk Beer Pizza All FREE! Where to find us? − Meetup − Facebook − Web Site
- 5. Why Log? Needed during development to identify errors, Needed during production for troubleshooting,
- 6. Requirements for a Logging Framework Logging should be easy for the developer to use, Logging should be flexible, Logging setup/config should be easy, especially for system administrators Configuration should be done at runtime, Framework should free you up to concentrate on the business/application logic
- 7. Reality of Logging Framework BUT − Logging frameworks are difficult to understand, − Logging frameworks are difficult to configure − Lots of heat but not much light when searching the Interwebs Why? − Competing frameworks, Part of Java community culture − Over engineered?
- 8. Why So Complex? Why are logging frameworks so complex? − Filtering of log messages to extract messages that meet system admin defined criteria, − Writing of a single log message to multiple destination, − Formatting log messages for different log back-ends such as text files, databases, email etc. − Ensuring logging has minimal impact on performance,
- 9. Why So Complex? − Integrating 3r party libraries with their own logging requirements, − Allowing for the runtime selection of logging frameworks, − Allowing for runtime configuration of the selected logging framework, − Applications are distributed
- 10. Well Known Java Logging Frameworks Log4j - The progenitor of all logging frameworks java.util.logging- The usurper. Attempted to add log4j to the Java JDK & improve on it. Jakarta Commons Logging - The failed abstractor. attempted to allow the underlying logging framework to be determined by the system administrator deploying the application
- 11. Well Known Java Logging Frameworks Simple Logging Façade for Java -The great abstractor. Some would call slf4j the saviour of Java logging. It is largely successful at abstracting away the underlying logging framework, allowing for it to be change at runtime with relative ease. Logback -The return of the jedi - This is the successor to the great progenitor log4j. Looks promising.
- 12. Other Java Logging Frameworks Even more logging frameworks, over 20! http://java-source.net/open-source/logging
- 13. What's missing? A conceptual model
- 14. Conceptual Model Logging Entities Interaction between entities Each framework has variations on the model
- 15. Conceptual Model Logging Entities Interaction between entities
- 16. Logging Entities Entity Description Log Manager Access point to logging system Log Message/Log Entry The log message Severity/Level A ranking of the log messages, also used as a filter criteria Logger A processing unit for the log message Appenders/Handlers A target to send the log message to Filters Criteria used to filter message Formatters/Renderers/Layouts Formatting of the log message for its handler/appender
- 17. Log Manager Global object to access logging system, Used to create or retrieve − Loggers − Handlers − Filters − Appenders − etc
- 18. Log Message The application message you wish to log. Can do things like: − Replace parameters at logging time, − Convert objects into string representations etc. Log messages have a severity attached to them Log messages are sent to a single Logger
- 19. Severity/Level Classification of the Log Message. Organised in a hierarchy of severity Lower level include higher level messages
- 20. Logger A logger is conceptually like a message queue A logger “processes” a log message Loggers are identified by string names Loggers are in a hierarchy determined identifier. Logger hierarchy set by “.” in logger identifier
- 21. Logger Every Logger has a parent, Root Logger is top of the logger hierarchy and always exists Loggers are source of complexity as Log messages “bubble up” the hierarchy Loggers can have severity levels to filter incoming log messages
- 22. Appenders/Handlers Represents a destination for a log method once it has been accepted by a Logger, Loggers can have more than one appender An appender can belong to more than one logger Appenders can be anything − Database − Text file − Console − Email
- 23. Filters A filter is a criteria against which incoming log messages are compared to be processed or discarded Filters can be on Loggers in some cases Filters can be on appenders, A filter can be attached to more than one appender/logger
- 24. Formatters/Layouts These entities format a log message for their assigned appenders, Add information to the log message like timestamp, class information etc Formatters/Layouts usually depend on the type of the appender
- 25. Sequence Diagram
- 26. How Log Messages Bubble Up Log messages received by a Logger and passed up the Logger hierarchy The exact flow varies from framework to framework Source of much confusion − Unwanted log messages in appenders,
- 29. Configuration Configuration can be done at compile time in code At runtime with configuration files At runtime via JMX
- 30. Meta Loggers Frameworks to abstract away Logging frameworks, Allow for run time changing of logging frameworks, Apache Commons Logging – not used due to architectural issues, Sl4j – Best meta logging framework
- 31. Meta Loggers SL4J allows for code to be written without concern for underlying framework − Change deployed jars to target different frameworks SL4J – allows for bridging of disparate logging frameworks in 3rd party libraries used in your application
- 32. Java Logging Frameworks The End