diff --git a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/AbstractUploadProgressListener.java b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/AbstractUploadProgressListener.java
index db1be59..0dcad26 100644
--- a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/AbstractUploadProgressListener.java
+++ b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/AbstractUploadProgressListener.java
@@ -25,7 +25,7 @@ public abstract class AbstractUploadProgressListener implements ProgressListener
 	/**
 	 *
 	 */
-	private static final long serialVersionUID = -7542788161740799624L;
+	private static final long serialVersionUID = -785329339005951465L;
 	private static final double COMPLETE_PERECENTAGE = 100d;
 	private int percentage = -1;
 
@@ -47,7 +47,8 @@ public abstract class AbstractUploadProgressListener implements ProgressListener
 		throw new RuntimeException("Implement the static method 'current' in your customized class");
 	}
 
-	protected Long bytesRead = 0L, contentLength = 0L;
+	protected Long bytesRead = 0L;
+	protected Long contentLength = 0L;
 	private String clientUploadKey;
 	// protected static HttpServletRequest request;
 	protected String sessionKey;
diff --git a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/UploadProgressInputStream.java b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/UploadProgressInputStream.java
index 92db636..aca6d14 100644
--- a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/UploadProgressInputStream.java
+++ b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/UploadProgressInputStream.java
@@ -19,8 +19,8 @@ import org.slf4j.LoggerFactory;
 public final class UploadProgressInputStream extends FilterInputStream {
 
   private List<ProgressListener> listeners;
-  private long bytesRead = 0;
-  private long totalBytes = 0;
+  private long bytesRead = 0L;
+  private long totalBytes = 0L;
   private static Logger logger = LoggerFactory.getLogger(UploadProgressInputStream.class);
 
   /**
diff --git a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/UploadProgressListener.java b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/UploadProgressListener.java
index ae6ab6d..9199e11 100644
--- a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/UploadProgressListener.java
+++ b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/server/upload/UploadProgressListener.java
@@ -144,8 +144,6 @@ public class UploadProgressListener extends AbstractUploadProgressListener {
 	}
 
 
-
-
 	/**
 	 * Instantiates a new upload listener.
 	 *
diff --git a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/shared/event/UploadEvent.java b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/shared/event/UploadEvent.java
index 40c117f..c89441f 100644
--- a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/shared/event/UploadEvent.java
+++ b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/shared/event/UploadEvent.java
@@ -12,25 +12,25 @@ public interface UploadEvent {
 	 *
 	 * @return the read percentage
 	 */
-	Integer getReadPercentage();
+	int getReadPercentage();
 
 	/**
 	 * Sets the read percentage.
 	 *
 	 * @param percentage the new read percentage
 	 */
-	void setReadPercentage(Integer percentage);
-	
-	
+	void setReadPercentage(int percentage);
+
+
 	/**
 	 * Sets the read time. (in millisecond)
-	 * 
+	 *
 	 * the difference, measured in milliseconds, between the current time and midnight, January 1, 1970 UTC.
 	 *
 	 * @param time the new read time
 	 */
 	void setReadTime(long time);
-	
+
 	/**
 	 * Gets the read time (in millisecond)
 	 *
diff --git a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/shared/event/UploadProgressChangeEvent.java b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/shared/event/UploadProgressChangeEvent.java
index b19321e..ce16211 100644
--- a/src/main/java/org/gcube/portlets/widgets/workspaceuploader/shared/event/UploadProgressChangeEvent.java
+++ b/src/main/java/org/gcube/portlets/widgets/workspaceuploader/shared/event/UploadProgressChangeEvent.java
@@ -11,11 +11,11 @@ import java.io.Serializable;
  */
 public final class UploadProgressChangeEvent implements UploadEvent, Serializable {
 	/**
-	 * 
+	 *
 	 */
 	private static final long serialVersionUID = -3445585716145899197L;
-	private Integer readPercentage = -1;
-	private long readTime = 0;
+	private int readPercentage = -1;
+	private long readTime = 0L;
 
 	/**
 	 * Instantiates a new upload progress change event.
@@ -26,7 +26,7 @@ public final class UploadProgressChangeEvent implements UploadEvent, Serializabl
 	/* (non-Javadoc)
 	 * @see org.gcube.portlets.widgets.workspaceuploader.shared.event.UploadEvent#getReadPercentage()
 	 */
-	public Integer getReadPercentage() {
+	public int getReadPercentage() {
 		return readPercentage;
 	}
 
@@ -34,17 +34,17 @@ public final class UploadProgressChangeEvent implements UploadEvent, Serializabl
 	/* (non-Javadoc)
 	 * @see org.gcube.portlets.widgets.workspaceuploader.shared.event.UploadEvent#setReadPercentage(java.lang.Integer)
 	 */
-	public void setReadPercentage(Integer percentage) {
+	public void setReadPercentage(int percentage) {
 		this.readPercentage = percentage;
 	}
-	
+
 	/* (non-Javadoc)
 	 * @see org.gcube.portlets.widgets.workspaceuploader.shared.event.UploadEvent#setReadTime(long)
 	 */
 	@Override
 	public void setReadTime(long time) {
 		this.readTime = time;
-		
+
 	}
 
 	/* (non-Javadoc)