Good day
I am having a hard time understanding how to use logging in Struts.
The struts.apache.org suggest the following usage (presumably for
business objects) (taken from:
http://struts.apache.org/1.x/userGuide/building_controller.html )
package com.foo;
// ...
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
...
public class User {
// ...
private static Log log =
LogFactory.getLog(User.class);
// ...
public void setBar(Bar bar) {
log.trace("Setting bar to " + bar);
this.bar = bar;
}
// ...
}
The suggestion seems to be that it is OK to declare my Logger as a
static variable in the business object. This is ideal for me because,
I will be accessing the Logger from both instance and static methods,
and so I do not want to have to declare this as an instance variable.
However, I am wondering whether this is OK, given that my business
objects will be being accessed from different servlet threads. Can
anyone tell me whether this is OK?, and if not, what is the correct way
to do this?
My second question is whether the same usage is valid for Action
classes. I saw the following example, at
http://www.mobilefish.com/developer/struts/struts_quickguide_log4j.html
but am not certain as to whether using a static variable would be OK
here. Would it?
public class DemoAction extends Action {
private static Log log =
LogFactory.getLog("com.mobilefish.DemoAction");
public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
log.debug("This is my debug message.");
log.info("This is my info message.");
log.warn("This is my warn message.");
log.error("This is my error message.");
log.fatal("This is my fatal message.");
}
}
The commons logging documentation notes the following:
Note that for application code, declaring the log member as "static" is
more efficient as one Log object is created per class, and is
recommended. However this is not safe to do for a class which may be
deployed via a "shared" classloader in a servlet or j2ee container or
similar environment. If the class may end up invoked with different
thread-context-classloader values set then the member must not be
declared static. The use of "static" should therefore be avoided in
code within any "library" type project.
I'm not clear as to what the above means, from a practical perspective
in the context of a web applicaiton. What does this mean in simple
terms?
Taken from:
http://jakarta.apache.org/commons/logging/guide.html#Configuring_Log4J
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