Next.js使用Prisma向SQLite提交表单数据调用create方法报错

错误场景 #

使用Prisma操作SQLite数据库写入doctor表数据时，触发如下报错：

Error: 
Invalid `prisma.doctor.create()` invocation:

{
  data: '{"id":"1","firstName":"ehshan","middleName":"ehhsns","lastName":"khan","gender":"Female","specialization":"Cardiologist","date":"2022-06-10","phoneNumber":"1234456112","address":"vfdgh dhyh ssvg"}'
        
}

Argument data: Got invalid value '{"id":"1","firstName":"ehshan","middleName":"ehhsns","lastName":"khan","gender":"Female","specialization":"Cardiologist","date":"2022-06-10","phoneNumber":"1234456112","address":"vfdgh dhyh ssvg"}' on prisma.createOneDoctor. 

Provided String, expected DoctorCreateInput or DoctorUncheckedCreateInput:
type DoctorCreateInput {
  id: String

  firstName: String

  middleName: String

  lastName: String

  gender: String

  specialization: String

  date: String

  phoneNumber: String

  address: String
}

错误根因 #

报错明确提示传入的data参数是字符串类型，但Prisma期望接收DoctorCreateInput或DoctorUncheckedCreateInput类型的结构化对象，问题出在接口代码的写法上。
原始错误代码：

import { PrismaClient,Prisma } from "@prisma/client"

const prisma = new PrismaClient();

export default async function handler(req, res) {
   
    let user = Prisma.DoctorCreateInput 
    user= JSON.stringify(req.body);
    const saveData = await prisma.doctor.create({
        data: user
    })

    res.json(saveData );
    //console.log(data)
}

代码存在两个明确问题：

• 错误使用Prisma导出的TS类型：Prisma.DoctorCreateInput是TypeScript类型，仅在编译阶段做类型校验，无法在JavaScript运行时作为变量赋值
• 错误序列化请求体：JSON.stringify(req.body)会把原本的请求体对象转换为JSON字符串，和Prisma要求的对象参数类型完全不匹配

修复方法 #

直接传入解析后的请求体对象即可，不需要做字符串转换，修复后的JS代码如下：

import { PrismaClient } from "@prisma/client"

const prisma = new PrismaClient();

export default async function handler(req, res) {
    // 直接使用框架自动解析好的req.body对象
    const saveData = await prisma.doctor.create({
        data: req.body
    })

    res.json(saveData);
}

补充说明 #

• 大部分Node.js API框架（Next.js、Express、NestJS等）默认都会自动解析JSON格式的请求体，req.body本身就是符合要求的JS对象，不需要额外做序列化操作
• 如果你手动关闭了框架的默认请求体解析，需要先执行JSON.parse(req.body)把请求体字符串转为JS对象，再传给Prisma
• 如果是TypeScript项目，可以引入类型做编译期校验，写法如下：

import { PrismaClient, DoctorCreateInput } from "@prisma/client"

const prisma = new PrismaClient();

export default async function handler(req, res) {
    const user = req.body as DoctorCreateInput;
    const saveData = await prisma.doctor.create({
        data: user
    })

    res.json(saveData);
}

内容的提问来源于stack exchange，提问作者mohd ehshan khan