Postman请求无法被Express服务识别字段，报错缺少必填项

使用Postman向Express后端发送用户注册数据时，后端抛出「Please Enter all the Fields」错误，以下是相关代码及信息：

Server文件 #

const express = require("express");
const { chats } = require("./data/data")
const dotenv = require("dotenv")
const { authMiddleware } = require('./util/auth');
const path = require('path');
const colors = require("colors")
const userRoutes = require("./routes/userRoutes")

const db = require('./config/connection.js');

const PORT = process.env.PORT || 5000;

const app = express();

app.use(express.json());
app.use(express.urlencoded({ extended: true }));


app.get('/',  (req,res) => {
   res.send("API is Running"); 
})



app.use('/api/user',userRoutes)

db.once('open', () => {
    app.listen(PORT, () => {
      console.log(`API server running on port ${PORT}!` .blue.bold);
    });
  });

User Controller文件 #

const asyncHandler = require("express-async-handler");
const generateToken = require("../config/generateToken");

const registerUser = asyncHandler(async (req, res) => {
    const { name, email, password, pic } = req.body;
     
     if (!name || !email || !password) {
      res.status(400);
      throw new Error("Please Enter all the Fields");
    }
  
    const userExists = await User.findOne({ email });
  
    if (userExists) {
      res.status(400);
      throw new Error("User already exists");
    }
  
    const user = await User.create({
      name,
      email,
      password,
      pic,
    });
  
    if (user) {
      res.status(201).json({
        _id: user._id,
        name: user.name,
        email: user.email,
        isAdmin: user.isAdmin,
        pic: user.pic,
        token: generateToken(user._id),
      });
    } else {
      res.status(400);
      throw new Error("User not found");
    }
    
  });
 
module.exports = { registerUser }

发送的JSON数据（存在语法错误） #

{
    "name": "examplename",
    "email": example"e@gmail.com",
    "password": "123456"
}

报错信息 #

Error: Please Enter all the Fields
    at C:\Users\doubl\OneDrive\Desktop\Messege Testing\server\Controllers\userControllers.js:9:13
    at asyncUtilWrap (C:\Users\doubl\OneDrive\Desktop\Messege Testing\node_modules\express-async-handler\index.js:3:20)
    at Layer.handle [as handle_request] (C:\Users\doubl\OneDrive\Desktop\Messege Testing\node_modules\express\lib\router\layer.js:95:5)
    at next (C:\Users\doubl\OneDrive\Desktop\Messege Testing\node_modules\express\lib\router\route.js:144:13)
    at Route.dispatch (C:\Users\doubl\OneDrive\Desktop\Messege Testing\node_modules\express\lib\router\route.js:114:3)
    at Layer.handle [as handle_request] (C:\Users\doubl\OneDrive\Desktop\Messege Testing\node_modules\express\lib\router\layer.js:95:5)
    at C:\Users\doubl\OneDrive\Desktop\Messege Testing\node_modules\express\lib\router\index.js:284:15
    at Function.process_params (C:\Users\doubl\OneDrive\Desktop\Messege Testing\node_modules\express\lib\router\index.js:346:12)
    at next (C:\Users\doubl\OneDrive\Desktop\Messege Testing\node_modules\express\lib\router\index.js:280:10)
    at Function.handle (C:\Users\doubl\OneDrive\Desktop\Messege Testing\node_modules\express\lib\router\index.js:175:3)

问题原因 #

1. JSON语法错误：发送的JSON中email字段格式错误，引号位置颠倒（写成了example"e@gmail.com"，正确格式应为"examplee@gmail.com"），导致express.json()中间件无法正确解析请求体，req.body中的name、email、password均为undefined，触发控制器中的字段非空检查，抛出错误。
2. 控制器缺失模型引入：User Controller中未引入User模型（如const User = require("../models/User")），后续执行User.findOne和User.create会引发新错误，但当前报错由JSON解析失败优先触发。

解决方法 #

1. 修正JSON数据格式：将发送的JSON中email字段修正为正确的字符串格式：

{
    "name": "examplename",
    "email": "examplee@gmail.com",
    "password": "123456"
}

2. 补充模型引入：在User Controller顶部添加User模型的引入代码，确保数据库操作能正常执行：

const User = require("../models/User"); // 根据实际模型文件路径调整

3. 调试请求体解析：可在Server文件中添加日志中间件，确认请求体是否被正确解析：

app.use((req, res, next) => {
  console.log("Parsed request body:", req.body);
  next();
});

内容的提问来源于stack exchange，提问作者Junior Cabriales