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How to programmatically configure applications or initialize logging in log4j2?

I am trying to configure appender programmatically, but have not yet succeeded. I just want to configure appender without a file so that it can send logs to the console or file.

String PATTERN = "%d [%p|%c|%C{1}] %m%n"; PatternLayout layout = PatternLayout.createLayout(PATTERN, null, null, null, null, null); ConsoleAppender console = ConsoleAppender.createAppender(layout, null, null, "console", "true", "true"); // create appender AppenderRef appender = AppenderRef.createAppenderRef("console", "DEBUG", null); logger = (Logger) LogManager.getLogger(InitLogger.class); LoggerContext context = logger.getContext(); BaseConfiguration configuration =(BaseConfiguration) context.getConfiguration(); configuration.addAppender(console); logger.addAppender(configuration.getAppender("console"));
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java logging log4j2
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2 answers

Here is the easiest way to do this:

 import org.apache.logging.log4j.Level; import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; import org.apache.logging.log4j.core.LoggerContext; import org.apache.logging.log4j.core.appender.ConsoleAppender; import org.apache.logging.log4j.core.config.AbstractConfiguration; import org.apache.logging.log4j.core.config.AppenderRef; import org.apache.logging.log4j.core.config.LoggerConfig; import org.apache.logging.log4j.core.layout.PatternLayout; public class Main { public static void main(String[] args) { configure(); Logger logger = LogManager.getLogger("com.company"); logger.trace("Hello Word!"); } public static void configure() { LoggerContext ctx = (LoggerContext) LogManager.getContext(false); AbstractConfiguration config = (AbstractConfiguration) ctx.getConfiguration(); ConsoleAppender appender = ConsoleAppender.createDefaultAppenderForLayout(PatternLayout.createDefaultLayout()); appender.start(); config.addAppender(appender); AppenderRef[] refs = new AppenderRef[] { AppenderRef.createAppenderRef(appender.getName(), null, null) }; LoggerConfig loggerConfig = LoggerConfig.createLogger("false", Level.ALL, LogManager.ROOT_LOGGER_NAME, "true", refs, null, config, null); loggerConfig.addAppender(appender, null, null); config.addLogger(LogManager.ROOT_LOGGER_NAME, loggerConfig); ctx.updateLoggers(); } }
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Try the following code example

 import org.apache.logging.log4j.Level; import org.apache.logging.log4j.core.appender.ConsoleAppender; import org.apache.logging.log4j.core.config.AppenderRef; import org.apache.logging.log4j.core.config.Configuration; import org.apache.logging.log4j.core.config.LoggerConfig; import org.apache.logging.log4j.core.layout.PatternLayout; import org.apache.logging.log4j.spi.ExtendedLogger; import org.apache.logging.log4j.spi.LoggerContext; public class TestLog4j2 { public static void main(String[] args) { try { ConsoleAppender console = ConsoleAppender.createAppender(PatternLayout.createDefaultLayout(), null, "SYSTEM_OUT", "console", null, null); final LoggerContext ctx = (LoggerContext) new org.apache.logging.log4j.core.LoggerContext("console" ); final Configuration config = ((org.apache.logging.log4j.core.LoggerContext) ctx).getConfiguration(); console.start(); config.addAppender(console); AppenderRef ref = AppenderRef.createAppenderRef("console", null, null); AppenderRef[] refs = new AppenderRef[] {ref}; LoggerConfig loggerConfig = LoggerConfig.createLogger("false", Level.ALL, "org.apache.logging.log4j", "true", refs, null, config, null ); loggerConfig.addAppender(console, null, null); config.addLogger("org.apache.logging.log4j", loggerConfig); ((org.apache.logging.log4j.core.LoggerContext) ctx).updateLoggers(); ExtendedLogger logger = (ExtendedLogger) ctx.getLogger("console"); logger.error("abc"); } catch (Exception e) { e.printStackTrace(); } } }
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