说明：Spring Boot中默认使用了Jackson做JSON的解析。
解决方法：
1、通过注入Bean来实现
错误：
org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: No serializer found for class com.google.common.cache.CacheStats and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)
解决：
@Bean public ObjectMapper objectMapper() { return new ObjectMapper().disable(SerializationFeature.FAIL_ON_EMPTY_BEANS); }
参考：
