3 files changed, 58 insertions, 16 deletions

diff --git a/server/src/com/vaadin/data/util/converter/ConverterUtil.java b/server/src/com/vaadin/data/util/converter/ConverterUtil.java
index 61d155bc9a..08d7363084 100644
--- a/server/src/com/vaadin/data/util/converter/ConverterUtil.java
+++ b/server/src/com/vaadin/data/util/converter/ConverterUtil.java
@@ -151,10 +151,14 @@ public class ConverterUtil implements Serializable {
 
     /**
      * Checks if the given converter can handle conversion between the given
-     * presentation and model type
+     * presentation and model type. Does strict type checking and only returns
+     * true if the converter claims it can handle exactly the given types.
+     * 
+     * @see #canConverterPossiblyHandle(Converter, Class, Class)
      * 
      * @param converter
-     *            The converter to check
+     *            The converter to check. If this is null the result is always
+     *            false.
      * @param presentationType
      *            The presentation type
      * @param modelType
@@ -168,10 +172,48 @@ public class ConverterUtil implements Serializable {
             return false;
         }
 
-        if (!modelType.isAssignableFrom(converter.getModelType())) {
+        if (modelType != converter.getModelType()) {
+            return false;
+        }
+        if (presentationType != converter.getPresentationType()) {
             return false;
         }
-        if (!presentationType.isAssignableFrom(converter.getPresentationType())) {
+
+        return true;
+    }
+
+    /**
+     * Checks if it possible that the given converter can handle conversion
+     * between the given presentation and model type somehow.
+     * 
+     * @param converter
+     *            The converter to check. If this is null the result is always
+     *            false.
+     * @param presentationType
+     *            The presentation type
+     * @param modelType
+     *            The model type
+     * @return true if the converter possibly support conversion between the
+     *         given presentation and model type, false otherwise
+     */
+    public static boolean canConverterPossiblyHandle(Converter<?, ?> converter,
+            Class<?> presentationType, Class<?> modelType) {
+        if (converter == null) {
+            return false;
+        }
+        Class<?> converterModelType = converter.getModelType();
+
+        if (!modelType.isAssignableFrom(converterModelType)
+                && !converterModelType.isAssignableFrom(modelType)) {
+            // model types are not compatible in any way
+            return false;
+        }
+
+        Class<?> converterPresentationType = converter.getPresentationType();
+        if (!presentationType.isAssignableFrom(converterPresentationType)
+                && !converterPresentationType
+                        .isAssignableFrom(presentationType)) {
+            // presentation types are not compatible in any way
             return false;
         }
 
diff --git a/server/src/com/vaadin/ui/AbstractField.java b/server/src/com/vaadin/ui/AbstractField.java
index 3bca63a3b7..606bf5fb21 100644
--- a/server/src/com/vaadin/ui/AbstractField.java
+++ b/server/src/com/vaadin/ui/AbstractField.java
@@ -616,17 +616,14 @@ public abstract class AbstractField<T> extends AbstractComponent implements
 
         // Check if the current converter is compatible.
         if (newDataSource != null
-                && !ConverterUtil.canConverterHandle(getConverter(), getType(),
-                        newDataSource.getType())) {
-            // Changing from e.g. Number -> Double should set a new converter,
-            // changing from Double -> Number can keep the old one (Property
-            // accepts Number)
-
-            // Set a new converter if there is a new data source and
-            // there is no old converter or the old is incompatible.
+                && !ConverterUtil.canConverterPossiblyHandle(getConverter(),
+                        getType(), newDataSource.getType())) {
+            // There is no converter set or there is no way the current
+            // converter can be compatible.
             setConverter(newDataSource.getType());
         }
-        // Gets the value from source
+        // Gets the value from source. This requires that a valid converter has
+        // been set.
         try {
             if (dataSource != null) {
                 T fieldValue = convertFromModel(getDataSourceValue());
diff --git a/server/src/com/vaadin/ui/Label.java b/server/src/com/vaadin/ui/Label.java
index d037652a09..d7cee2a80d 100644
--- a/server/src/com/vaadin/ui/Label.java
+++ b/server/src/com/vaadin/ui/Label.java
@@ -242,14 +242,17 @@ public class Label extends AbstractComponent implements Property<String>,
             ((Property.ValueChangeNotifier) dataSource).removeListener(this);
         }
 
+        // Check if the current converter is compatible.
         if (newDataSource != null
-                && !ConverterUtil.canConverterHandle(getConverter(),
-                        String.class, newDataSource.getType())) {
-            // Try to find a converter
+                && !ConverterUtil.canConverterPossiblyHandle(getConverter(),
+                        getType(), newDataSource.getType())) {
+            // There is no converter set or there is no way the current
+            // converter can be compatible.
             Converter<String, ?> c = ConverterUtil.getConverter(String.class,
                     newDataSource.getType(), getSession());
             setConverter(c);
         }
+
         dataSource = newDataSource;
         if (dataSource != null) {
             // Update the value from the data source. If data source was set to