Custom Log Level | 易学教程

问题

In my existing application "org.apache.log4j" API's have been used in java code.

Requirement :

I have to log some statement(say xyz) in log file in any case and should not dependent of log levels.For example : if my log level is error then also xyz should print, if my log level is debug then also xyz should print.

I cannot make log statement of xyz is debug because if i do this, other log statements apart from xyz will also start printing.

For this, I believe, I have to add some custom log level.Please help how to do it and how to set its level ordering so that in any case it should print.

Thanks in advance. Best Regards

回答1:

What you could do is create a different Logger for those statements (you are not restricted to use classes names when defining a logger)

// Standard logger
private static Logger log = Logger.getLogger(MyClass.class)

// XYZ logger
private static Logger logXYZ = Logger.getLogger("logs.xyz");

You can access the same logger from several class, you just have to pass the same label.

Then, in the configuration file, you can define a different log level for that category, and even output these logs in a different appender (different file, processing, etc.)

回答2:

You could "hijack" the protected method Logger#forcedLog() to always print to the log.

You must place the hijacker class in the same package as Logger.

package org.apache.log4j;

/**
 * @author maba, 2012-08-23
 */
public class LogOverride {
    public static void print(Logger logger, String message) {
        logger.forcedLog(logger.getName(), Priority.INFO, message, null);
    }
}

And from your calling code

log.setLevel(Level.OFF); // Make sure logging is turned off
log.info("Normal logging"); // Will not be seen anywhere
LogOverride.print(log, "Overriding logger"); // Will still make it to your appender

This is what the log4j FAQ says about custom levels:

How do I add a custom level?

It is possible, but rarely appropriate. The request is commonly for a level named something like "audit" that doesn't obviously fit in the progression "trace", "debug", "info", "warn", "error" and "fatal". In that case, the request for a level is really a request for a mechanism to specify a different audience. The appropriate mechanism is to use a distinct logger name (or tree) for "audit" related messages.

So if you want to go with that suggestion then you should look at the answer from SJuan76.

回答3:

If you do decide to go with the idea of creating a custom, you would need to create a subclass of Level to do this, because the Level constructor is protected.

/**
 * Instantiate a Level object.
 */
 protected Level(int level, String levelStr, int syslogEquivalent) {
     super(level, levelStr, syslogEquivalent);
 }

It looks like you should then chain to the Level constructor, passing it a suitable level value. Note that the larger the level number the higher the priority is. So for a Level that won't be blocked at any of the existing named levels, you want a value that is greater than Priority.FATAL_INT which is 50000.

(However, I'm not convinced that this is the right approach. For a start, you probably won't be able to refer to your custom level by name in a logging config file.)

来源：https://stackoverflow.com/questions/12089902/custom-log-level

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java

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logging

log4j