diff --git a/scm-dao-xml/src/main/java/sonia/scm/store/FileBasedStore.java b/scm-dao-xml/src/main/java/sonia/scm/store/FileBasedStore.java
index 0d1d250ce7..07a841a777 100644
--- a/scm-dao-xml/src/main/java/sonia/scm/store/FileBasedStore.java
+++ b/scm-dao-xml/src/main/java/sonia/scm/store/FileBasedStore.java
@@ -199,5 +199,5 @@ public abstract class FileBasedStore<T> implements StoreBase<T>
   protected File directory;
 
   /** Field description */
-  private String suffix;
+  private final String suffix;
 }
diff --git a/scm-dao-xml/src/main/java/sonia/scm/store/FileBasedStoreFactory.java b/scm-dao-xml/src/main/java/sonia/scm/store/FileBasedStoreFactory.java
index 989878a722..5fff61de3a 100644
--- a/scm-dao-xml/src/main/java/sonia/scm/store/FileBasedStoreFactory.java
+++ b/scm-dao-xml/src/main/java/sonia/scm/store/FileBasedStoreFactory.java
@@ -105,11 +105,11 @@ public class FileBasedStoreFactory
   //~--- fields ---------------------------------------------------------------
 
   /** Field description */
-  private SCMContextProvider context;
+  private final SCMContextProvider context;
 
   /** Field description */
   private File dataDirectory;
 
   /** Field description */
-  private String dataDirectoryName;
+  private final String dataDirectoryName;
 }
diff --git a/scm-dao-xml/src/main/java/sonia/scm/store/FileBlob.java b/scm-dao-xml/src/main/java/sonia/scm/store/FileBlob.java
index 8452956ea9..9c4cba88d9 100644
--- a/scm-dao-xml/src/main/java/sonia/scm/store/FileBlob.java
+++ b/scm-dao-xml/src/main/java/sonia/scm/store/FileBlob.java
@@ -46,7 +46,7 @@ import java.io.OutputStream;
  *
  * @author Sebastian Sdorra
  */
-public class FileBlob implements Blob
+public final class FileBlob implements Blob
 {
 
   /**
@@ -122,8 +122,8 @@ public class FileBlob implements Blob
   //~--- fields ---------------------------------------------------------------
 
   /** Field description */
-  private File file;
+  private final File file;
 
   /** Field description */
-  private String id;
+  private final String id;
 }
diff --git a/scm-dao-xml/src/main/java/sonia/scm/store/FileBlobStore.java b/scm-dao-xml/src/main/java/sonia/scm/store/FileBlobStore.java
index aae0cdf8b3..690c42fb33 100644
--- a/scm-dao-xml/src/main/java/sonia/scm/store/FileBlobStore.java
+++ b/scm-dao-xml/src/main/java/sonia/scm/store/FileBlobStore.java
@@ -142,7 +142,7 @@ public class FileBlobStore extends FileBasedStore<Blob> implements BlobStore
   @Override
   public void remove(Blob blob)
   {
-    Preconditions.checkNotNull("blob argument is required");
+    Preconditions.checkNotNull(blob, "blob argument is required");
     remove(blob.getId());
   }
 
@@ -196,6 +196,6 @@ public class FileBlobStore extends FileBasedStore<Blob> implements BlobStore
 
   //~--- fields ---------------------------------------------------------------
 
-  /** Field description */
-  private KeyGenerator keyGenerator;
+  /** key generator */
+  private final KeyGenerator keyGenerator;
 }
diff --git a/scm-dao-xml/src/main/java/sonia/scm/store/FileBlobStoreFactory.java b/scm-dao-xml/src/main/java/sonia/scm/store/FileBlobStoreFactory.java
index 82fc587d0b..93d525026c 100644
--- a/scm-dao-xml/src/main/java/sonia/scm/store/FileBlobStoreFactory.java
+++ b/scm-dao-xml/src/main/java/sonia/scm/store/FileBlobStoreFactory.java
@@ -98,6 +98,6 @@ public class FileBlobStoreFactory extends FileBasedStoreFactory
 
   //~--- fields ---------------------------------------------------------------
 
-  /** Field description */
-  private KeyGenerator keyGenerator;
+  /** key generator */
+  private final KeyGenerator keyGenerator;
 }