Made failure message customizable.

spring-data-commons-core/src/main/java/org/springframework/data/persistence/AbstractConstructorEntityInstantiator.java

@@ -57,12 +57,16 @@ public abstract class AbstractConstructorEntityInstantiator<BACKING_INTERFACE, S
     private <T extends BACKING_INTERFACE> StateBackedCreator<T, STATE> createFailingInstantiator(final Class<STATE> stateType) {
         return new StateBackedCreator<T, STATE>() {
             public T create(STATE n, Class<T> c) throws Exception {
-                throw new IllegalArgumentException(getClass().getSimpleName() + ": entity " + c +
-                        " must have either a constructor taking [" + stateType + "] or a no-arg constructor and state set method");
+                throw new IllegalArgumentException(getFailingMessageForClass(c, stateType));
             }
         };
     }
 
+    protected String getFailingMessageForClass(Class<?> entityClass, Class<STATE> stateClass) {
+        return getClass().getSimpleName() + ": entity " + entityClass +
+                " must have either a constructor taking [" + stateClass + "] or a no-arg constructor and state setter.";
+    }
+
     private <T extends BACKING_INTERFACE> StateBackedCreator<T, STATE> emptyConstructorStateSettingInstantiator(Class<T> type, Class<STATE> stateType) {
         final Constructor<T> constructor = getNoArgConstructor(type);
         if (constructor == null) return null;