code: @SuppressWarnings("unchecked")
      public <T> TypeHandler<T> getInstance(Class<?> javaTypeClass, Class<?> typeHandlerClass) {
          if (javaTypeClass != null) {
            try {
              Constructor<?> c = typeHandlerClass.getConstructor(Class.class);
              return (TypeHandler<T>) c.newInstance(javaTypeClass);
            } catch (NoSuchMethodException ignored) {
              // ignored
            } catch (Exception e) {
              throw new TypeException("Failed invoking constructor for handler " + typeHandlerClass, e);
            }
          }
          try {
            Constructor<?> c = typeHandlerClass.getConstructor();
            return (TypeHandler<T>) c.newInstance();
          } catch (Exception e) {
            throw new TypeException("Unable to find a usable constructor for " + typeHandlerClass, e);
          }
        }
docs: 实例化TypeHandler
  @param javaTypeClass
  @param typeHandlerClass
  @return