I know I can set the logback.xml path like this:
Specifying the location of the default configuration file as a system property
You may specify the location of the default configuration file with a system property named "logback.configurationFile". The value of this property can be a URL, a resource on the class path or a path to a file external to the application.
java -Dlogback.configurationFile=/path/to/config.xml chapters.configuration.MyApp1
but how can I do it in code?
LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();
loggerContext.reset();
JoranConfigurator configurator = new JoranConfigurator();
InputStream configStream = FileUtils.openInputStream(logbackPropertiesUserFile);
configurator.setContext(loggerContext);
configurator.doConfigure(configStream); // loads logback file
configStream.close();