NodeJS 使用 Mongoose 与 MongoDB 连接

Question

我正在尝试通过访问 localhost:4000/books 在浏览器 URL 中查看 mongodb 集合（只是为了查看）

app.js 代码：

var express = require("express");
var app = express();
var bodyParser = require("body-parser");
var mongoose = require("mongoose");
var Book = require("./book.model");

//mongo DB database connection: databse nmae is: example
var db = "mongodb://localhost:27017/example";
mongoose.connect(db, { useNewUrlParser: true, useUnifiedTopology: true });

const conSuccess = mongoose.connection
conSuccess.once('open', _ => {
  console.log('Database connected:', db)
})

conSuccess.on('error', err => {
  console.error('connection error:', err)
})

var port = 4000;
app.listen(port, function () {
  console.log("app listening on port " + port);
});
//REST get
app.get('/', function(req,res){
  res.send("happy to be here");
});

//work on here localhost:4000 works but not localhost?4000/books
//get all "books" collections
app.get('/books', function(req,res) {
  console.log("get all books");
  Book.find({})
  exec(function(err, books){
    if(err){
      res.send("error has occured");
    } else {
      console.log(books);
      res.json(books);
    }
  }); 
});

book.model.js

var mongoose = require("mongoose");
var Schema = mongoose.Schema;

var BookSchema = new Schema({
  title: String,
  author: String,
  category: String,
});

module.exports = mongoose.model("Book", BookSchema);

mongodb 服务器在 cmd propt 中启动

ran> 节点应用 控制台显示消息为 “应用程序监听 4000 端口 数据库连接：mongodb://localhost:27017/example"

在 URL 中，当我尝试这样访问时 本地主机：4000/书

将错误显示为

引用错误：exec 未定义。为什么会这样，请帮助解决这个问题。我正在努力纠正这个错误 3 天，并在没有继续前进的情况下真正解决这个问题。

Answer 1

在exec之前使用.就这样尝试

app.get('/books', function(req,res) {
  console.log("get all books");
  Book.find({}).exec(function(err, books){
    if(err){
      res.send("error has occured");
    } else {
      console.log(books);
      res.json(books);
    }
  }); 
});