Programmatically add appender in logback

Question

I am trying to add an appender dynamically in logback. Here is my code.

LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
PatternLayoutEncoder ple = new PatternLayoutEncoder();
ple.setPattern("%date %level [%thread] %logger{10} [%file:%line] %msg%n");
ple.setContext(lc);
ple.start();
FileAppender<ILoggingEvent> fileAppender = new FileAppender<ILoggingEvent>();
String logFile = "new.log";
fileAppender.setFile(logFile);
fileAppender.setEncoder(ple);
fileAppender.setContext(lc);
fileAppender.start();

ch.qos.logback.classic.Logger logbackLogger =
                (ch.qos.logback.classic.Logger)LoggerFactory.getLogger(ModuleMessageHandler.class);
logbackLogger.addAppender(fileAppender);
logbackLogger.setLevel(Level.DEBUG);
logbackLogger.setAdditive(false);

It works ok but works only for the specific logger on which the appender is added. Is there a way to get this to work for all loggers in the application? I am looking for a way to dynamically add and remove appenders.

you want to get the root logger. Logger root = (Logger)LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME); — Bill O'Neil, Nov 15 '17 at 05:32

score 12 · Accepted Answer · answered Nov 15 '17 at 08:01

This section of your code:

LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
PatternLayoutEncoder ple = new PatternLayoutEncoder();
ple.setPattern("%date %level [%thread] %logger{10} [%file:%line] %msg%n");
ple.setContext(lc);
ple.start();
FileAppender<ILoggingEvent> fileAppender = new FileAppender<ILoggingEvent>();
String logFile = "new.log";
fileAppender.setFile(logFile);
fileAppender.setEncoder(ple);
fileAppender.setContext(lc);
fileAppender.start();

... creates and starts the file appender.

This section of your code ...

ch.qos.logback.classic.Logger logbackLogger =
                (ch.qos.logback.classic.Logger)LoggerFactory.getLogger(ModuleMessageHandler.class);
logbackLogger.addAppender(fileAppender);
logbackLogger.setLevel(Level.DEBUG);
logbackLogger.setAdditive(false);

... associates the file appender with the logger instance for ModuleMessageHandler.

If, instead, you want the file appender to be associated with all logger instances in your application then (as @BillO'Neil) suggested you must associate the file appender with the root logger:

ch.qos.logback.classic.Logger logbackLogger =
                (ch.qos.logback.classic.Logger)LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);
logbackLogger.addAppender(fileAppender);

The setAdditive(true) means that the appender is treated as an additional appender. Thus the log message can be seen in multiple logs. When setAdditive(false) it only is used by this appender. — user2209562, Jan 31 '23 at 14:17

Programmatically add appender in logback

1 Answers1

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