Liferay中的记录器无法正常工作

我正在使用Liferay 6.20和tomcat.

根据这篇文章:Liferay:登录Liferay的默认方法是什么？我已经在我的基本portlet类中添加了一个记录器,如下所示:

package mypackage.katalog;

import java.io.IOException;

import javax.portlet.ActionRequest;
import javax.portlet.ActionResponse;
import javax.portlet.PortletException;

import com.liferay.portal.kernel.log.Log;
import com.liferay.portal.kernel.log.LogFactoryUtil;
import com.liferay.util.bridges.mvc.MVCPortlet;

/**
 * Portlet implementation class KatalogUslugPortlet
 */
public class KatalogUslugPortlet extends MVCPortlet {
    private static Log _log = LogFactoryUtil.getLog(KatalogUslugPortlet.class);

    @Override
    public void processAction(ActionRequest actionRequest,
            ActionResponse actionResponse) throws IOException, PortletException {

        testLogger();

        super.processAction(actionRequest, actionResponse);
    }

    private void testLogger() {
        System.out.print("SYSTEM_OUT!!!");

        _log.info("INFO!!!");
        _log.debug("DEBUG!!!");
        _log.error("ERROR!!!");
    }
}

并且日志既不出现在控制台中,也不出现在tomcat日志中.怎么可能出错？