com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class xxx and no properties discovered to create BeanSerializer

使用objectMapper.writeValuesAsString()时报错

这是报错的代码

我报错的理由是自定义的bean Area没有写getter方法。