PostgreSQL Node.js实现函数计算方法示例

const { Pool } = require('pg');
const config = require('../config/default.js');
const {
 database: {
 HOST,
 PORT,
 DATABASE,
 USERNAME,
 PASSWORD,
 },
} = config;
const pool = new Pool({
 port: PORT,
 host: HOST,
 user: USERNAME,
 password: PASSWORD,
 database: DATABASE,
});
/**
 * 
 * @param sql 接收的sql语句
 * @param {Array} values sql语句参数
 * @return { Object } { success: boolean, err || data }
 */
const query = async function( sql = 'select NOW()', values = []) {
 return new Promise(resolve => {
 pool.connect((err, client, release) => {
 if (err) {
 return console.error('Error acquiring client', err.stack)
 }
 const params = Array.isArray(values) "htmlcode">

const config = {
 // 数据库配置
 database: {
 DATABASE: 'databasename',
 USERNAME: 'root',
 PASSWORD: '123456',
 PORT: '3433',
 HOST: 'localhost',
 },
};

module.exports = config;


Controller
BaseController
首先编写一个基类，用于封装一些通用的方法


const pool = require('../lib/postgre'); // 导入封装好的mysql库
const { query } = pool; // 导入query方法
class BaseController {
 constructor() {
 }
 // 查询表内所有数据（非删除）
 async list() {
 const sql = `select * from ${this.table}`;
 return await query(sql);
 }
 async excute(sql, vals = []) {
 // 执行方法
 return await query(sql, vals);
 }
 // log 方法
 log({func, err}) {
 console.log(`excute function[${func}] occured error : ${err.message || err}`);
 }
}

module.exports = BaseController;


InqueryController
具体的业务逻辑Controller类


const BaseController = require('./BaseController'); // 获得基类
// 继承基类
class InqueryController extends BaseController {
 constructor() {
 super();
 this.table = 'data_table'; // 赋值table
 }
 // 可以重写基类的方法，如果有业务需要
 async list() {
 const sql = `select * from ${this.table} ORDER BY created_at DESC `;
 return await this.excute(sql);
 }
 async getUnsendCustomer(vals) {
 const sql = `select * from ${this.table} where created_at > $1 ORDER BY created_at DESC`;
 // 统一在基类调用sql参数
 return await this.excute(sql, vals);
 }
 
}
module.exports = InqueryController;


Service
BaseService
统一封装的方法，基类


// 需要绑定this的方法
const funcs = [
 'list',
]
class BaseService {
 constructor() {
 this.controller = null;
 // 循环遍历绑定this, 在koa绑定route的时可用到
 funcs.forEach(item => {
  this[item] = this[item].bind(this)
 });
 }

 // 查询方法
 async list(ctx) {
 if (!ctx) {
  return await this.controller.list();
 }
 // controller返回的是一个对象，success(成功为true， 失败为false), data(成功则有此数据), err(失败则有此对象)
 const { success: flag, data, error } = await this.controller.list();
 if (flag) {
  // success
  ctx.body = {
  data,
  code: 200,
  }
 } else {
  // failed
  ctx.body = {
  code: 500,
  error,
  };
 }
 }
}

module.exports = BaseService


InqueryService
具体的业务逻辑


// 导入基类
const BaseService = require('./BaseService');
// 导入对应的controller
const Controller = require('../controller/InqueryController');
// 获取MailSender Service
const MailService = require('./MailSender');
const Helper = require('../util/Helper');

const funcs = [
 'unsendUser',
];
// 生成一次controller
const controller = new Controller();
class InqueryService extends BaseService {
 constructor() {
 super()
 // 绑定对应的controller
 this.controller = controller;
 funcs.forEach(item => {
  this[item] = this[item].bind(this);
 });
 }
 getMailOpts(i) {
 // you can use the data from database to combine the message
 const message = 'Hello world!';
 return return {
  message,
  // 可以从配置文件读取或者oss
  to: 'xxxx@gmail.com',
  subject: 'Hello World',
 };
 }
 
 async unsendUser() {
 const list = await this.controller.list();
 if (list.length > 0) {
  const mailer = new MailService();
  const errorList = [];
  iterateList.forEach(async i => {
  const mailerOption = this.getMailOpts(i);
  const { success, ...rest } = await mailer.sendToAuitAdmin(mailerOption);
  if (!success) {
   errorList.push(rest);
  }
  });
  const lastestTime = iterateList[0].created_at;
  if (errorList.length === 0) {
  return {
   code: 200,
   message: 'Success',
  };
  }
 } else {
  return {
  code: 204,
  message: 'No user found',
  };
 }
 }
}
module.exports = new InqueryService();


index.js
函数计算的逻辑


const inqueryService = require('./services/InqueryService'); 
exports.handler = async function(event, context, callback) {
 const result = await inqueryService.unsendUser();
 callback(null, result);
};


总结
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