Setting logback.xml path programmatically

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();

You could use:

System.setProperty("logback.configurationFile", "/path/to/config.xml");

But it would have to happen before logback is loaded, i.e. something like:

class Main {
  static { System.setProperty("logback.configurationFile", "/path/to/config.xml");}
  private final Logger LOG = LoggerFactory.getLogger(Main.class);

  public void main (String[] args) { ... }
}

Note: I have not tested it but it should work.

modifying environment variables might not always be feasible. To do it properly see logback manual:

http://logback.qos.ch/manual/configuration.html#joranDirectly

I just want to share what I did in the end with a Jersey-Spring app:

MyWebApplicationInitializer implements WebApplicationInitializer {
    @Override
    public void onStartup(final ServletContext servletContext) throws ServletException {
        servletContext.addListener(new LogbackConfigListener());
        try { LogbackConfigurer.initLogging(servletContext.getRealPath("/WEB-INF/logback.xml")); }
        catch (FileNotFoundException | JoranException e) { e.printStackTrace(); }
    }
}

I also have to add, that I had to move

<dependency>
    <groupId>org.logback-extensions</groupId>
    <artifactId>logback-ext-spring</artifactId>
    <version>0.1.4</version>
    <scope>compile</scope></dependency>
<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-core</artifactId>
    <version>1.2.3</version>
    <scope>compile</scope></dependency>

from runtime (parent project in my case) to compile.

Include another logback xml to change path in logback-spring.xml

include resource = "/path/to/logback.xml"

add data within included tags in logback.xml