Index: src/gui/CMakeLists.txt
===================================================================
--- src/gui/CMakeLists.txt	(revision 15556)
+++ src/gui/CMakeLists.txt	(working copy)
@@ -89,6 +89,7 @@
 qgslegendinterface.h
 qgisinterface.h
 qgsencodingfiledialog.h
+qgsfieldvalidator.h
 qgsformannotationitem.h
 qgsgenericprojectionselector.h
 qgsmapcanvas.h
Index: src/gui/qgsattributeeditor.cpp
===================================================================
--- src/gui/qgsattributeeditor.cpp	(revision 15556)
+++ src/gui/qgsattributeeditor.cpp	(working copy)
@@ -23,6 +23,7 @@
 #include <qgscategorizedsymbolrendererv2.h>
 #include <qgssymbol.h>
 #include <qgslonglongvalidator.h>
+#include <qgsfieldvalidator.h>
 
 #include <QPushButton>
 #include <QLineEdit>
@@ -357,20 +358,9 @@
           le->setCompleter( c );
         }
 
-        if ( myFieldType == QVariant::Int )
-        {
-          le->setValidator( new QIntValidator( le ) );
-        }
-        else if ( myFieldType == QVariant::LongLong )
-        {
-          le->setValidator( new QgsLongLongValidator( le ) );
-        }
-        else if ( myFieldType == QVariant::Double )
-        {
-          le->setValidator( new QDoubleValidator( le ) );
-        }
-
+        le->setValidator( new QgsFieldValidator( le, field ) );
         myWidget = le;
+
       }
 
       if ( te )
@@ -460,7 +450,7 @@
   {
     text = le->text();
     modified = le->isModified();
-    if ( text == nullValue )
+    if ( text == nullValue || text == "NULL" || text == "null" )
     {
       text = QString::null;
     }
Index: qgsfieldvalidator.h
===================================================================
--- qgsfieldvalidator.h	(revision 0)
+++ qgsfieldvalidator.h	(revision 0)
@@ -0,0 +1,137 @@
+/***************************************************************************
+                         qgsfieldvalidator.h  -  description
+                             -------------------
+    begin                : March 2011
+    copyright            : (C) 2011 by SunilRajKiran-kCube
+    email                : sunilraj.kiran@kcubeconsulting.com
+
+  adapted version of QValidator for QgsField
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+/* $Id$ */
+
+#ifndef QGSFIELDVALIDATOR_H
+#define QGSFIELDVALIDATOR_H
+
+#include <QMessageBox>
+#include <QValidator>
+#include <QLocale>
+#include <QVariant>
+
+#include "qgslogger.h"
+#include "qgslonglongvalidator.h"
+#include "qgsfield.h"
+
+class GUI_EXPORT QgsFieldValidator : public QValidator
+{
+   Q_OBJECT     
+
+public:
+QgsFieldValidator(QObject *parent,  const QgsField &field, int t, int b):QValidator(parent)
+{
+	fieldLength = field.length();
+	fieldPrecision = field.precision();
+	fieldType = field.type();
+	
+	switch(fieldType)
+	{
+		case QVariant::Int :
+			validator = new QIntValidator(b, t, parent);
+			break;
+		case QVariant::Double :
+			validator = new QDoubleValidator(parent);
+			break;
+		case QVariant::LongLong :
+			validator = new QgsLongLongValidator(b, t, parent);
+			break;
+		default:
+			validator = 0;
+	}
+
+}
+
+QgsFieldValidator(QObject *parent, const QgsField &field):QValidator(parent)
+{
+	fieldLength = field.length();
+	fieldPrecision = field.precision();
+	fieldType = field.type();
+	
+	switch(fieldType)
+	{
+		case QVariant::Int :
+			validator = new QIntValidator(parent);
+			break;
+		case QVariant::Double :
+			validator = new QDoubleValidator(parent);
+			break;
+		case QVariant::LongLong :
+			validator = new QgsLongLongValidator(parent);
+			break;
+		default:
+			validator = 0;
+	}	
+}
+
+~QgsFieldValidator()
+{
+  delete validator;	
+}
+
+QValidator::State validate(QString &s, int &i) const
+{
+		
+	if(validator && validator->validate(s, i) == Invalid)
+	{
+		return Invalid;
+	}
+	
+	if(validator && validator->validate(s, i) == Intermediate)
+	{
+		if(s.length() > fieldLength)
+		return Invalid;
+		return Intermediate;
+	}
+	
+	if ( fieldType == QVariant::String ) 
+	{
+	  if (s.length() > 1 )
+	  {
+	    if ( s == "NU" || s == "NUL" || s == "NULL" || s == "nu" || s == "nul" || s == "null")
+	    return Intermediate;	  
+	  }
+  }
+  
+	if(s.length() > fieldLength)
+		return Invalid;
+	
+	if(fieldType == QVariant::Double)
+	{
+		int len = s.length();
+		int prec = s.indexOf(QChar('.'));
+		QgsDebugMsg(tr("length %1 %2") . arg(len). arg(prec));
+		if(s.indexOf(QChar('.')) != -1 && s.length() - (s.indexOf(QChar('.')) + 1) > fieldPrecision)
+			return Invalid;
+	}
+	
+	return Acceptable;
+}
+
+private:
+    // Disables copy constructing
+    Q_DISABLE_COPY( QgsFieldValidator )   
+     
+    QValidator *validator;
+    int fieldLength;
+    QVariant::Type fieldType;
+    int fieldPrecision;
+};
+
+#endif // QGSFIELDVALIDATOR_H