Java Reference
In-Depth Information
run.log4jdemo:
[java] 1 [main] INFO com.darwinsys - I created an object: java.lang.
Object@bb6086
BUILD SUCCESSFUL
Total time: 1 second
A more typical use of logging might be to catch an Exception and log it, as shown in
Example 16-12 .
Example 16-12. Log4j—catching and logging
public
public class
class Log4JDemo2
Log4JDemo2 {
public
public static
static void
void main ( String [] args ) {
Logger theLogger = Logger . getLogger ( "com.darwinsys" );
try
try {
Object o = new
new Object ();
theLogger . info ( "I created an object: " + o );
iif ( o != null
null ) {
// bogus, just to show logging
throw
throw new
new IllegalArgumentException ( "Just testing" );
}
} catch
catch ( Exception ex ) {
theLogger . error ( "Caught Exception: " + ex , ex );
}
}
}
Much of the flexibility of the log4j package stems from its use of external configuration
files; you can enable or disable logging without recompiling the application. A properties file
that eliminates all logging might have this entry:
log4j.rootLogger=FATAL, APP1
Only fatal error messages print; all levels less than that are ignored.
To log from a client to a server on a remote machine, the org.apache.log4j.net package
includes several Appender s and servers to connect them to.
For more information on log4j , visit its website . log4j is free software, distributed under
the Apache Software Foundation license.
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