本篇介绍在执行MySQL线上变更时遇到的问题，表现为"更新JSON字段时，实际更新的值与SQL语句中的值不一致，JSON格式错误"，如下；

问题描述

处理线上问题，需要新插入一条记录；将原JSON粘贴出来，修改部分字段，然后提交SQL更新语句，原始JSON如下：

{
    "playerQualifyType": 1,
    "surveyId": 14,
    "playerRegisterEndTime": 1670860799000,
    "planName": "《碧蓝大陆》先锋测试招募！",
    "planStatus": 2,
    "playerRegisterStartTime": 1669860000000,
    "gameName": "碧蓝大陆",
    "developerName": "海南羽弘信息技术有限公司",
    "planStartTime": 1673316000000,
    "qualificationCodeUrl": "",
    "updateTime": 1669777099000,
    "planPlayerNum": 1500,
    "extend": "{\"innerDesc\":\"\",\"planId\":16,\"verifyOperator\":\"Akira-11126666\",\"verifyResultDesc\":\"\",\"verifyResultDescImgList\":[],\"verifyResultStatus\":2,\"verifyTime\":1669777099887}",
    "planEndTime": 1673884800000,
    "pkgStatus": 0
}

现提交SQL变更单，执行SQL语句如下：

update t set `json_field` = 
'
{
    "playerQualifyType": 1,
    "surveyId": 14,
    "playerRegisterEndTime": 1670860799000,
    "planName": "《碧蓝大陆》先锋测试招募！",
    "planStatus": 2,
    "playerRegisterStartTime": 1669860000000,
    "gameName": "碧蓝大陆",
    "developerName": "海南羽弘信息技术有限公司",
    "planStartTime": 1673316000000,
    "qualificationCodeUrl": "",
    "updateTime": 1669777099000,
    "planPlayerNum": 1500,
    "extend": "{\"innerDesc\":\"\",\"planId\":16,\"verifyOperator\":\"Akira-11126666\",\"verifyResultDesc\":\"\",\"verifyResultDescImgList\":[],\"verifyResultStatus\":2,\"verifyTime\":1669777099887}",
    "planEndTime": 1673884800000,
    "pkgStatus": 0
}
'
where id = 55;

结果数据库中更新后查出来的纪录如下，不满足JSON格式了，仔细检查发现是extend字段的值中的反斜杠全部没有了，JSON解析失败；

{
    "playerQualifyType": 1,
    "surveyId": 14,
    "playerRegisterEndTime": 1670860799000,
    "planName": "《碧蓝大陆》先锋测试招募！",
    "planStatus": 2,
    "playerRegisterStartTime": 1669860000000,
    "gameName": "碧蓝大陆",
    "developerName": "海南羽弘信息技术有限公司",
    "planStartTime": 1673316000000,
    "qualificationCodeUrl": "",
    "updateTime": 1669777099000,
    "planPlayerNum": 1500,
    "extend": "{"innerDesc":"","planId":16,"verifyOperator":"Akira-11126666","verifyResultDesc":"","verifyResultDescImgList":[],"verifyResultStatus":2,"verifyTime":1669777099887}",
    "planEndTime": 1673884800000,
    "pkgStatus": 0
}

问题排查

联系DBA描述问题，得到的回复是——

\"相当于就转义成 "了，这是MySQL自身处理的结果；

实验如下：

而代码中执行的就没问题，原因是代码中该字段对应的Java类型为String，也就是说原JSON的外层因为套了一层双引号""，因此还会有一次转义符的嵌套，如下；

\"extend\":\"{\\\"innerDesc\\\":\\\"\\\",\\\"planId\\\":16,\\\"verifyOperator\\\":\\\"Akira-11126666\\\",\\\"verifyResultDesc\\\":\\\"\\\",\\\"verifyResultDescImgList\\\":[],\\\"verifyResultStatus\\\":2,\\\"verifyTime\\\":1669777099887}\"

因此，代码中执行JSON字符串的MySQL插入，实际入库的值与预期一致；正确的SQL如下：

update t set `json_field` = 
'
{\"playerQualifyType\":1,\"surveyId\":14,\"playerRegisterEndTime\":1670860799000,\"planName\":\"《碧蓝大陆》先锋测试招募！\",\"planStatus\":2,\"playerRegisterStartTime\":1669860000000,\"gameName\":\"碧蓝大陆\",\"developerName\":\"海南羽弘信息技术有限公司\",\"planStartTime\":1673316000000,\"qualificationCodeUrl\":\"\",\"updateTime\":1669777099000,\"planPlayerNum\":1500,\"extend\":\"{\\\"innerDesc\\\":\\\"\\\",\\\"planId\\\":16,\\\"verifyOperator\\\":\\\"Akira-11126666\\\",\\\"verifyResultDesc\\\":\\\"\\\",\\\"verifyResultDescImgList\\\":[],\\\"verifyResultStatus\\\":2,\\\"verifyTime\\\":1669777099887}\",\"planEndTime\":1673884800000,\"pkgStatus\":0}
'
where id = 55;

解决方案

在更新Mysql表的JSON字符串字段时，步骤应该如下：

1. 输入查询语句，找到目标记录，复制JSON字段的值到JSON编辑工具中修改JSON中的属性值

2. 将修改后的JSON粘贴到IDE中，IDE用双引号接收这一串JSON；

3. 执行SQL时，SQL语句中的值以IDE中被双引号包裹的字符串值为SQL中的新的value；

    // 将JSON粘贴进来 整体作为SQL更新语句中的新的value 这里也可以不格式化JSON
    String formatValue = "{\n" +
            "    \"playerQualifyType\": 1,\n" +
            "    \"surveyId\": 14,\n" +
            "    \"playerRegisterEndTime\": 1670860799000,\n" +
            "    \"planName\": \"《碧蓝大陆》先锋测试招募！\",\n" +
            "    \"planStatus\": 2,\n" +
            "    \"playerRegisterStartTime\": 1669860000000,\n" +
            "    \"gameName\": \"碧蓝大陆\",\n" +
            "    \"developerName\": \"海南羽弘信息技术有限公司\",\n" +
            "    \"planStartTime\": 1673316000000,\n" +
            "    \"qualificationCodeUrl\": \"\",\n" +
            "    \"updateTime\": 1669777099000,\n" +
            "    \"planPlayerNum\": 1500,\n" +
            "    \"extend\": \"{\\\"innerDesc\\\":\\\"\\\",\\\"planId\\\":16,\\\"verifyOperator\\\":\\\"Akira-11126666\\\",\\\"verifyResultDesc\\\":\\\"\\\",\\\"verifyResultDescImgList\\\":[],\\\"verifyResultStatus\\\":2,\\\"verifyTime\\\":1669777099887}\",\n" +
            "    \"planEndTime\": 1673884800000,\n" +
            "    \"pkgStatus\": 0\n" +
            "}";
    
    // 未格式化 会少去/n换行符
    String value = "{\"playerQualifyType\":1,\"surveyId\":14,\"playerRegisterEndTime\":1670860799000,\"planName\":\"《碧蓝大陆》先锋测试招募！\",\"planStatus\":2,\"playerRegisterStartTime\":1669860000000,\"gameName\":\"碧蓝大陆\",\"developerName\":\"海南羽弘信息技术有限公司\",\"planStartTime\":1673316000000,\"qualificationCodeUrl\":\"\",\"updateTime\":1669777099000,\"planPlayerNum\":1500,\"extend\":\"{\\\"innerDesc\\\":\\\"\\\",\\\"planId\\\":16,\\\"verifyOperator\\\":\\\"Akira-11126666\\\",\\\"verifyResultDesc\\\":\\\"\\\",\\\"verifyResultDescImgList\\\":[],\\\"verifyResultStatus\\\":2,\\\"verifyTime\\\":1669777099887}\",\"planEndTime\":1673884800000,\"pkgStatus\":0}";