京公网安备11010502063487号返回对象时日期、大整数、null 到底写成什么?前端传各种写法的日期会发生什么,哪些会悄悄出错?XML 请求怎么办?Boot 4 换成 Jackson 3 之后哪些配置要改?这篇在 Spring Boot 4.0.8 上逐项验证。
day → "2026-10-19" dt → "2026-10-19T14:30:05" at → "2026-10-19T06:30:05Z" zdt → "2026-10-19T14:30:05+08:00" legacy → "2026-10-19T06:30:05.000Z" big → (JSON 数字) 9007199254740993 dec → (JSON 数字) 12345678901234567890.12 d → (JSON 数字) 0.30000000000000004 color → "GREEN" nul → null opt → null emptyList → [] 响应头 Content-Type: application/json 说明:Java 里 big=9007199254740993L,在 JSON 里写成了数字,JavaScript 的 JSON.parse 会把它读成 9007199254740992(超过 2^53 的整数丢精度)。下面用 Python 的 float 模拟:float(9007199254740993) = 9007199254740992
日期写成 ISO 字符串,大整数写成数字,null 和 Optional.empty 都写成 null。
正常 → 200 收到 In[day=2026-10-19, dt=2026-10-19T14:30:05, at=2026-10-19T06:30:05Z, legacy=Mon Oct 19 14:30:05 CST 2026, big=1, color=RED] day 写成 2026/10/19 → 400 HttpMessageNotReadableException: JSON parse error: Cannot deserialize value of type `java.time.LocalDate` from String "2026/10/19": Failed to deserialize `java.time.Local day 写成时间戳数字 → 400 HttpMessageNotReadableException: JSON parse error: Failed to deserialize java.time.LocalDate from epoch day value 1792391405000: Invalid value for EpochDay (valid values dt 带时区后缀 Z → 200 收到 In[day=null, dt=2026-10-19T14:30:05, at=null, legacy=null, big=null, color=null] at 写成秒级数字 → 200 收到 In[day=null, dt=null, at=2026-10-19T06:30:05Z, legacy=null, big=null, color=null] at 写成毫秒级数字 → 200 收到 In[day=null, dt=null, at=+58768-08-15T21:23:20Z, legacy=null, big=null, color=null] legacy 写成毫秒数字 → 200 收到 In[day=null, dt=null, at=null, legacy=Mon Oct 19 14:30:05 CST 2026, big=null, color=null] color 写小写 red → 400 HttpMessageNotReadableException: JSON parse error: Cannot deserialize value of type `Color` from String "red": not one of the values accepted for Enum class: [RED, GREEN] color 写不存在的 BLUE → 400 HttpMessageNotReadableException: JSON parse error: Cannot deserialize value of type `Color` from String "BLUE": not one of the values accepted for Enum class: [RED, GREEN 未知字段 extra → 200 收到 In[day=null, dt=null, at=null, legacy=null, big=null, color=null] big 写成字符串 "123" → 200 收到 In[day=null, dt=null, at=null, legacy=null, big=123, color=null] big 写成小数 1.5 → 200 收到 In[day=null, dt=null, at=null, legacy=null, big=1, color=null]
有的写法明确 400,有的写法悄悄通过却丢了信息或值错了。
GET /text → 200 中文 ok Content-Type: text/plain;charset=UTF-8 GET /sample Accept: application/xml → 406 GET /xml-only(produces application/xml,返回 String)→ 200 <a/> Content-Type: application/xml;charset=UTF-8
String 直接按文本写出,没有 XML 转换器时 Accept: application/xml 得 406。
spring.jackson.default-property-inclusion=non_null:字段 ['day', 'dt', 'at', 'zdt', 'legacy', 'big', 'dec', 'd', 'color', 'opt', 'emptyList'];day="2026-10-19",at="2026-10-19T06:30:05Z",legacy="2026-10-19T06:30:05.000Z" spring.jackson.datatype.datetime.write-dates-as-timestamps=true:字段 ['day', 'dt', 'at', 'zdt', 'legacy', 'big', 'dec', 'd', 'color', 'nul', 'opt', 'emptyList'];day=[2026, 10, 19],at=1792391405.0,legacy=1792391405000 spring.jackson.serialization.write-dates-as-timestamps=true(Jackson 2 时代的写法)→ 启动失败:Failed to bind properties under 'spring.jackson.serialization' to java.util.Map<SerializationFeature, java.lang.Boolean>:;failed to convert java.lang.String to SerializationFeature (caused by java.lang.IllegalArgumentException: No enum constant SerializationFeature.write-dates-as-timestamps)
Jackson 3 把日期开关挪到了 datatype.datetime 下。