Chapter 9: Using the Apache Log Tag Library - BeKnowledge

Chapter 9: Using the Apache Log Tag Library
� Changing the threshold level for the root logger or other custom loggers used with any of the tags
can cause changes in the logging output.
Note If no separate logger (Category) is explicitly specified as an attribute of any of the Log tags, the
tags rely on the root logger of log4j to publish logging information. Hence, it is always safe to keep
the root logger configuration even though we may specify custom logger (Category) names within
the tag attributes and configure them separately in the same configuration file.
Setting the Environment
Having followed the instructions in the "Installing the Log Tag Library" section, we are all ready to use
the Log tag library from within a JSP. Before we can see the example JSP in Listing 9-1 in action, we
need to configure the Web server to use the JSP and the log4j configuration file as described in next few
steps:
1. First, put the JPS described in Listing 9-1 into a folder named "TestLogTags" (or any folder of
your choice) under the "webapps" directory of the Tomcat installation.
2. In Tomcat, any Web application typically contains a "WEB-INF" directory and one "WEB-
INF/classes" directory. Place the "log4j.properties" file in one of these locations. For example,
you may decide to put it in the "WEB-INF/classes" directory.
3. Specify where Tomcat can find the configuration file shown in the preceding section for log4j.
4. Pass the "log4j.properties" file as a system variable to the execution environment of Tomcat.
5. Go to the "tomcat.bat" file in "%TOMCAT_HOME%\bin".
6. Add an entry to set the classpath variable to point to the directory containing the "log4j.properties"
file. For this example, the entry may read as follows:
set CP=%CP%;C:\Jakarta-tomcat-3.2.1\webapps\
TestLogTags\WEB-INF\classes
7. Add the following entry to the "tomcat.bat" file:
set TOMCAT_OPTS=-Dlog4j.configuration=log4j.properties
Note We can also configure log4j through an initialization servlet. Consult Chapter 5 for more on this
topic.
This is all we need to do before we can run the example, which we will see how to do next.
The Log Example in Action
Now start up Tomcat and access the JSP page, as shown in Figure 9-1. Tomcat will load the
"log4j.properties" file, and Log will use this configuration file to print the logging information.
file://C:\Documents and Settings\deepak\Local Settings\Temp\~hh572B.htm
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