Blee Blee - 4 months ago 32
Java Question

log4j add prefix to all messages from one abstract class

I am trying to use log4j to add prefix to all log commands.

Previously I have been using @Slf4j in front of all classes, but now I need to add certain prefix to all messages, so this is no longer possible.

My class structure is as follows:

abstract class MyAbstractClass {
protected final MyLogger log;
MyAbstractClass(String foodType) {
this.log = new MyLogger(Logger.getLogger(this.getClass(), foodType));
}
}

class MyClass1 extends MyAbstractClass {
MyClass1(String foodType) { super(foodType); }
public static void myMethod1() {
log.info("hehe");
}
}

class MyClass2 extends MyAbstractClass {
MyClass2(String foodType) { super(foodType); }
public static void myMethod2() {
log.info("hohohoho");
}
}

/* MyLogger.java */

@Slf4j
public class MyLogger {
private final Logger LOGGER;
private String PREFIX;
public MyLogger(Logger logger, String foodType) {
LOGGER = logger;
PREFIX = foodType + ": ";
}

public void info(final String str) {
log.info(PREFIX + str);
}

public void warn(final String str) {
log.warn(PREFIX + str);
}

public void debug(final String str) { log.debug(PREFIX + str); }

public void error(final String str) {
log.error(PREFIX + str);
}

public void error(final String str, Exception e) {
log.error(PREFIX + str, e);
}
...

// i know.. it's so inconvenient because I have to override all the methods that I want to use from log4j Logger. I wish there is an alternative.

}


If I were to do something like this,

public static void main() {
MyClass1 c1 = new MyClass1("burger");
MyClass2 c2 = new MyClass2("pizza");
c1.myMethod1();
c2.myMethod2();
}


I would get something like this.

/* console */
[INFO] MyLogger#info - burger: hehe
[INFO] MyLogger#info - pizza: hohoho


BUT, i would like to get something like this to be able to trace where exactly it came from (original Log4j does this).

/* console */
[INFO] MyClass1#MyMethod1 - burger: hehe
[INFO] MyClass2#MyMethod2 - pizza: hohoho


Is there way for me to accomplish this?

Thanks!

Answer

I solved this by using the MDC Pattern. I no longer need MyLogger class. I can just use the Log4j 's Logger class.

You can do something like

abstract class MyAbstractClass {
    protected final Logger log;
    MyAbstractClass(String foodType) {
        MDC.put("myfood", foodType);
        this.log = LoggerFactory.getLogger(getClass()));
    }
}

and in the pattern, you can add on %X{myfood} to access the variables you set :)

More on MDC here: http://logback.qos.ch/manual/mdc.html