Nodejs中mongodb的使用及封装

const { MongoClient } = require('mongodb');
 
class Database {
  constructor(url) {
    this.connection = null;
    this.url = url;
  }
 
  async connect() {
    if (this.connection) {
      throw new Error('Cannot open a new connection.');
    }
    try {
      this.connection = await MongoClient.connect(this.url, { useNewUrlParser: true, useUnifiedTopology: true });
      console.log('Connected to database.');
    } catch (error) {
      console.error('Error connecting to database:', error);
    }
  }
 
  collection(name) {
    if (!this.connection) {
      throw new Error('No connection established to database.');
    }
    return this.connection.db().collection(name);
  }
 
  close() {
    if (this.connection) {
      this.connection.close();
      this.connection = null;
      console.log('Connection to database closed.');
    }
  }
}
 
module.exports = Database;

这段代码定义了一个名为Database的类，它封装了连接MongoDB数据库的细节。它提供了一个connect方法来建立连接，一个collection方法来获取指定名称的集合，以及一个close方法来关闭连接。使用时，只需创建Database类的实例并调用相应的方法。