TilesContextBeanELResolver extends ELResolver { @Override public Class<?> getCommonPropertyType(ELContext context, Object base) { if (base != null) { return null; } return String.class; }  @Override Class<?> getCommonPropertyType(ELContext context, Object base); @Override Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context,
            Object base); @Override Class<?> getType(ELContext context, Object base, Object property); @Override Object getValue(ELContext context, Object base, Object property); @Override boolean isReadOnly(ELContext context, Object base, Object property); @Override void setValue(ELContext context, Object base, Object property,
            Object value);  }
@Test public void testGetCommonPropertyType() { Class<?> clazz = resolver.getCommonPropertyType(null, null); assertEquals("The class is not correct", String.class, clazz); clazz = resolver.getCommonPropertyType(null, "Base object"); assertNull("The class for non root objects must be null", clazz); }