diff --git a/src/main/java/net/onrc/onos/ofcontroller/core/internal/DeviceStorageImpl.java b/src/main/java/net/onrc/onos/ofcontroller/core/internal/DeviceStorageImpl.java
index 386c1bd..63eaacb 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/core/internal/DeviceStorageImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/core/internal/DeviceStorageImpl.java
@@ -24,7 +24,7 @@
 public class DeviceStorageImpl implements IDeviceStorage {
 	
 	private GraphDBOperation ope;
-	protected static Logger log = LoggerFactory.getLogger(SwitchStorageImpl.class);
+	protected final static Logger log = LoggerFactory.getLogger(SwitchStorageImpl.class);
 
 	/***
 	 * Initialize function. Before you use this class, please call this method
diff --git a/src/main/java/net/onrc/onos/ofcontroller/core/internal/LinkStorageImpl.java b/src/main/java/net/onrc/onos/ofcontroller/core/internal/LinkStorageImpl.java
index 8ee346b..b32a26e 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/core/internal/LinkStorageImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/core/internal/LinkStorageImpl.java
@@ -24,7 +24,7 @@
  */
 public class LinkStorageImpl implements ILinkStorage {
 	
-	protected static Logger log = LoggerFactory.getLogger(LinkStorageImpl.class);
+	protected final static Logger log = LoggerFactory.getLogger(LinkStorageImpl.class);
 	protected GraphDBOperation dbop;
 
 	/**
diff --git a/src/main/java/net/onrc/onos/ofcontroller/core/internal/SwitchStorageImpl.java b/src/main/java/net/onrc/onos/ofcontroller/core/internal/SwitchStorageImpl.java
index b7c97f8..e184423 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/core/internal/SwitchStorageImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/core/internal/SwitchStorageImpl.java
@@ -18,7 +18,7 @@
  */
 public class SwitchStorageImpl implements ISwitchStorage {
 	protected GraphDBOperation op;
-	protected static Logger log = LoggerFactory.getLogger(SwitchStorageImpl.class);
+	protected final static Logger log = LoggerFactory.getLogger(SwitchStorageImpl.class);
 	
 	/***
 	 * Initialize function. Before you use this class, please call this method
diff --git a/src/main/java/net/onrc/onos/ofcontroller/core/internal/TopoLinkServiceImpl.java b/src/main/java/net/onrc/onos/ofcontroller/core/internal/TopoLinkServiceImpl.java
index e810646..b692e8e 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/core/internal/TopoLinkServiceImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/core/internal/TopoLinkServiceImpl.java
@@ -18,7 +18,7 @@
 public class TopoLinkServiceImpl implements ITopoLinkService {
 	
 	protected GraphDBOperation op;
-	protected static Logger log = LoggerFactory.getLogger(TopoLinkServiceImpl.class);
+	protected final static Logger log = LoggerFactory.getLogger(TopoLinkServiceImpl.class);
 
 	public void finalize() {
 		close();
diff --git a/src/main/java/net/onrc/onos/ofcontroller/core/internal/TopoSwitchServiceImpl.java b/src/main/java/net/onrc/onos/ofcontroller/core/internal/TopoSwitchServiceImpl.java
index cd3cf15..1f39a38 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/core/internal/TopoSwitchServiceImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/core/internal/TopoSwitchServiceImpl.java
@@ -11,7 +11,7 @@
 public class TopoSwitchServiceImpl implements ITopoSwitchService {
 	
 	private GraphDBOperation op;
-	protected static Logger log = LoggerFactory.getLogger(TopoSwitchServiceImpl.class);
+	protected final static Logger log = LoggerFactory.getLogger(TopoSwitchServiceImpl.class);
 
 	public TopoSwitchServiceImpl(String conf) {
 		op = new GraphDBOperation(conf);