code: public static String getDefaultConversionFor(String javaType)
      {
          return _jdbcConversions.containsKey(javaType) ? (String)_jdbcConversions.get(javaType) : null;
      }
docs: Returns the default conversion for the given java type.
  
  @param javaType The qualified java type
  @return The default conversion or <code>null</code> if there is no default conversion for the type