=== modified file 'dhis-2/dhis-web/dhis-web-api/src/main/java/org/hisp/dhis/api/controller/DataValueSetController.java'
--- dhis-2/dhis-web/dhis-web-api/src/main/java/org/hisp/dhis/api/controller/DataValueSetController.java	2012-03-02 12:39:20 +0000
+++ dhis-2/dhis-web/dhis-web-api/src/main/java/org/hisp/dhis/api/controller/DataValueSetController.java	2012-03-19 15:52:41 +0000
@@ -27,6 +27,10 @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+import java.io.IOException;
+
+import javax.servlet.http.HttpServletResponse;
+
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.hisp.dhis.api.webdomain.DataValueSets;
@@ -36,6 +40,7 @@
 import org.springframework.security.access.prepost.PreAuthorize;
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.Model;
+import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
@@ -68,4 +73,11 @@
         log.debug( "Saved data value set for data set: " + dataValueSet.getDataSetIdentifier() +
             ", org unit: " + dataValueSet.getOrganisationUnitIdentifier() + ", period: " + dataValueSet.getPeriodIsoDate() );
     }
+    
+    @ExceptionHandler(IllegalArgumentException.class)
+    public void handleException( HttpServletResponse response, IllegalArgumentException ex )
+        throws IOException
+    {
+        response.sendError( HttpServletResponse.SC_CONFLICT, ex.getMessage() );
+    }
 }