json中的时区问题

jackson在处理date类型时，如果不指定时区，则会默认去UTC。当系统时间不是UTC时（东八区为GMT+8），容易造成和正确时间不符合的情况。问题常见于springmvc接受json时间参数等场景。

        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
        TimeZone timeZone = objectMapper.getSerializationConfig().getTimeZone();
        System.out.println(timeZone);//未设置时，默认时区为UTC
//sun.util.calendar.ZoneInfo[id="UTC",offset=0,dstSavings=0,useDaylight=false,transitions=0,lastRule=null]

    @PostMapping("timezone-vo")
    public String timezone_vo(@RequestBody TimeVo vo) {
        log.info(vo.toString());
        return JSON.toJSONString(vo, SerializerFeature.WriteDateUseDateFormat);
    }

    @Test
    public void timezone_vo() throws Exception {
        Map param = new HashMap();
        param.put("time", "2019-07-19");

        ObjectMapper mapper = new ObjectMapper();
        mockMvc.perform(MockMvcRequestBuilders.post("/json/timezone-vo")
                .contentType(MediaType.APPLICATION_JSON).content(mapper.writeValueAsString(param)))
                .andExpect(MockMvcResultMatchers.status().isOk())
                .andDo(print());
        //Body = {"time":"2019-07-19 08:00:00"}
    }