Log statements are sent to a Logger which in turn writes to one or more
Appenders. First you must get a Logger. Most people use the class name
as the name of the logger:
namespace Company.Project
{
public class Foo
{
ILog log = LogManager.GetLogger(typeof(Foo));
public void TestMethod()
{
log.Debug("Hello World");
}
}
}
Then in your log4net file you decide what Appenders the Logger should
write to. The text below will write output to the MyFileAppender
Appender:
<logger name="Company.Project.Foo">
<appender-ref ref="MyFileAppender" />
</logger>
MyFileAppender is defined as:
<appender name="MyFileAppender" type="log4net.Appender.FileAppender">
<file value="c:\log.txt">
<appendToFile value="false" />
<layout type="log4net.Layout.SimpleLayout" />
</appender>
You should see the following line in your output file:
DEBUG - Hello World
People usually include much more information in their log entries. For
example, this is what I use for a FileAppenders:
<appender name="MyFileAppender" type="log4net.Appender.FileAppender">
<file value="c:\log.txt">
<appendToFile value="false" />
<layout type="log4net.Layout.PatternLayout,log4net">
<conversionPattern value="%5p %d{yyyy-MM-dd hh:mm:ss tt} (%c:%L) -
%m%n" />
</layout>
</appender>
That conversionPattern will record a log statement with information
such as the log level, time of the log event, the class, the line
number where the log originated from, and my message:
INFO 2005-06-02 05:53:55 PM (Company.Project.Global:85) - Application
started
A very common error when people first start using log4net is that they
have not made the destination directory for log files writtable.
The <logger> node I used above will only snag log messages generated by
the Company.Project.Foo class. If you want to log message from other
classes or from Loggers that weren't created from classes:
ILog auditLog = LogManager.GetLog("AUDIT");
You can use the more general root logger:
<root>
<appender-ref ref="MyFileAppender" />
</root>
Every log4net config file requires there be a root logger. You may
define additional <logger> nodes as necessary. The example below will
write logs belonging to the "AUDIT" Logger to one destination and logs
belonging to Company.Project.Foo to another destination.
<!-- required -->
<root>
<appender-ref ref="AuditFileAppender" />
</root>
<!-- optional -->
<logger name="Company.Project.Foo">
<appender-ref ref="MyFileAppender" />
</logger>
Its also possible to write the output from a Logger to more than one
destination:
<root>
<appender-ref ref="MyFileAppender" />
</root>
<logger name="AUDIT">
<appender-ref ref="MyEmailAppender" />
<appender-ref ref="DatabaseAppender" />
</logger>
Suppose I have other classes in the Company.Project namespace: Bar,
Baz, and Boo. I can use this syntax to capture log statements from all
4 classes:
<logger name="Company.Project">
<appender-ref ref="MyFileAppender" />
</logger>
To answer your second question, you can store additional pieces of
information that you want to appear on the log messages by using the
ThreadContext:
log4net.ThreadContext.Properties["UserId"] = userId;
log4net.ThreadContext.Properties["WindowsVersion"] = windowsVersion;
log.Debug("Hello World");
log.Debug("World Hello");
To reference these values in your appender you would do this:
<appender name="MyFileAppender" type="log4net.Appender.FileAppender">
<file value="c:\log.txt">
<appendToFile value="false" />
<layout type="log4net.Layout.PatternLayout,log4net">
<conversionPattern value="%p %d %property{UserId} - %m%n" />
</layout>
</appender>
Log4net already comes with many pre-defined patterns:
http://tinyurl.com/e3nd3
http://logging.apache.org/log4net/release/sdk/log4net.Layout.PatternLayout.html
Its easy to define custom patterns:
<conversionPattern value="%p %d %querystring{ProductId} - %m%n" />
<conversionPattern value="%p %d %foo{Bar} - %m%n" />
<conversionPattern value="%p %d %minutes-till-lunch - %m%n" />
How do you intend to "flag" your message when you write it to the
Logger?
log.DebugFormat("This message is flagged: {0}", ???);
Its possible to add new log levels to log4net:
log.Flag("This is a special message.");
You could setup a special Appender that only records "flagged"
messages.
All of the above examples involving xml could be translated to code.
Its possible to deploy log4net without a config file.
--- Weston Weems <[EMAIL PROTECTED]> wrote:
> I've just begun to play with log4net after trying endlessly to get
> Enterprise Library working as I'd like it.
>
> I do have a few questions I was unable to find the answers for on my
> own (reading documentation/manual on logging.apache.org)
>
> this is all .net 1.1 and using 1.9b or whatever the latest build was.
>
> 1) is there a way to explicitly from code tell my log entry to use a
> specific appender?
>
> 2) For adoappender, is there way to provide more properties of a log
> entry, and log that into more columns etc? Eg, if I wanted to include
> username, version of windows etc.
>
> 3) from config file, is there somethinga little more finegrained for
> routing error messages than levels and string matches? I'd like to be
> able to "flag" an error message and if the config permits, have it
> processed with a specific appender. (I realize I could use the filter
> and filter on a string I throw in there, just seems cumbersome)
>
>
> Anyway thank you guys very much
> Weston Weems
>
