Chapter 9: Using the Apache Log Tag Library - BeKnowledge

Chapter 9: Using the Apache Log Tag Library
This configuration file defines the configuration for the logger test. The test logger has a threshold
level of DEBUG and uses a RollingFileAppender object to print logging information to a file named
"logtags.log". Notice that the conversionPattern to format the logging information includes the name
of the logger (%c).
Using this configuration file for Log will write information to the "logtags.log" file in the "%
TOMCAT_HOME%\bin" directory. If we execute the example JSP with this modified configuration
file, we will see the following output in the "logtags.log" file:
DEBUG Thread-11 root - Message embedded within open and close tags.
DEBUG Thread-11 root - Message passed as an attribute to the tag
INFO Thread-11 test - Hello how are you?
This is how we can use different loggers with custom configuration to handle logging information. If we
specify the category attribute in the JSP but do not specify a configuration for it, Log will use the root
logger configuration to handle the logging request.
Description of Log Tags
The Log tag library provides tags corresponding to the levels declared in log4j. Table 9-1 summarizes all
the Log tag library tags and their attributes.
Table 9-1: Summary of Log Tags
Tag Name Tag Description Attribute Name Required
debug Displays a DEBUG-level message category message No
No
info Displays an INFO-level message category message No
No
warn Displays a WARN-level message category message No
No
error Displays a ERROR-level message category message No~
No
fatal Displays a FATAL-level message category message No
No
dump Displays all the variables in a specified scope scope Yes
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As you can see, the use of these Log tags is very simple. All the tags except dump have two optional
attributes, category and message. It is possible to specify the logging information as a value of the
message attribute or by enclosing it within the tag. For example, we can use the error tag in following
two ways:
file://C:\Documents and Settings\deepak\Local Settings\Temp\~hh572B.htm
6/14/2010