diff --git a/src/main/scala/app/GitRepositoryServlet.scala b/src/main/scala/app/GitRepositoryServlet.scala
index 91c71b0..8fecbe2 100644
--- a/src/main/scala/app/GitRepositoryServlet.scala
+++ b/src/main/scala/app/GitRepositoryServlet.scala
@@ -7,6 +7,7 @@
 import org.eclipse.jgit.api.Git
 import org.eclipse.jgit.lib.Ref
 import org.eclipse.jgit.http.server.GitServlet
+import org.slf4j.LoggerFactory
 
 /**
  * Provides Git repository via HTTP.
@@ -16,6 +17,9 @@
  */
 class GitRepositoryServlet extends GitServlet {
 
+  private val logger = LoggerFactory.getLogger(classOf[GitRepositoryServlet])
+  
+  // TODO are there any other ways...?
   override def init(config: ServletConfig): Unit = {
     super.init(new ServletConfig(){
       def getInitParameter(name: String): String = name match {
@@ -38,8 +42,7 @@
   override def service(request: HttpServletRequest, response: HttpServletResponse): Unit = {
     super.service(request, response)
     
-    // TODO debug log
-    println(request.getMethod + ": " + request.getRequestURI)
+    logger.debug(request.getMethod + ": " + request.getRequestURI)
     
     // update branches
     if(request.getMethod == "POST" && request.getRequestURI.endsWith("/git-receive-pack")){
diff --git a/src/main/scala/util/AutoUpdate.scala b/src/main/scala/util/AutoUpdate.scala
index 0e66b1a..6fa1843 100644
--- a/src/main/scala/util/AutoUpdate.scala
+++ b/src/main/scala/util/AutoUpdate.scala
@@ -18,7 +18,7 @@
    */
   case class Version(majorVersion: Int, minorVersion: Int){
     
-    val logger = LoggerFactory.getLogger(classOf[Version])
+    private val logger = LoggerFactory.getLogger(classOf[Version])
     
     /**
      * Execute update/MAJOR_MINOR.sql to update schema to this version.
@@ -88,7 +88,7 @@
  */
 class AutoUpdateListener extends org.h2.server.web.DbStarter {
   import AutoUpdate._
-  val logger = LoggerFactory.getLogger(classOf[AutoUpdateListener])
+  private val logger = LoggerFactory.getLogger(classOf[AutoUpdateListener])
   
   override def contextInitialized(event: ServletContextEvent): Unit = {
     super.contextInitialized(event)