Hello world! In this article we will learn how to create a rest api using postgresql and expressjs. We will use javascript for this project.
First let us know what are the pre-requisites for this project:-
One must have:
- the basic knowledge of javascript and nodejs
- must be familiar with basic crud operations
- must be familiar with sql commands
- must have a basic knowledge of expressjs
Useful links
- https://nodejs.dev/en/learn/
- https://www.postgresql.org/docs/current/sql-commands.html
- http://expressjs.com/
Installer links
- NodeJS:https://nodejs.org/en/download/
- Postgresql:https://www.postgresql.org/download/
First we will initialize the project folder with a "package.json".
npminit-yThen we will install express, cors (for allowing cross origin requests) & pg (to connect to postgresql).
npmiexpresscorspgThen we will install nodemon as a dev dependency to reload our server automatically.
Do not use nodemon in production servers
npmi-DnodemonBefore connecting to database, we will first create the database
- Create a database and name it of your own choice.
- Then go into the schemas and right click on tables. Give a name of "blogs" to your table.
- Create the specified columns for the table
Create a file "db.js", where we will connect to the database
const{Pool}=require('pg');constpool=newPool({host:'localhost',user:'username',password:'password',port:5432,database:'db_name'})module.exports=pool;Now let's create a folder called routes and create a file "blog.js" inside it.
Then make the required imports
constexpress=require('express');constrouter=express.Router();constpool=require('../db');The first api route will be to query all the blogs from the database. We will usepool.query('') to run our sql commands.
router.get('/',async(req,res)=>{letblogs=awaitpool.query('SELECT * FROM blogs ORDER BY blogs.timestamp ASC');// Order posts by ascending orderres.status(200).json({status:200,totalResults:blogs.rowCount,blogs:blogs.rows});})Then the second api route will be to query a specific blog from the database.
router.get('/:slug',async(req,res)=>{letblog=awaitpool.query(`SELECT * FROM blogs WHERE slug='${req.params.slug}'`);if(blog.rowCount===0){res.status(404).json({status:404,message:'No such blog was found!'});}else{res.status(200).json({status:200,blog:blog.rows});}})Then the third api route will be to add a blog to the database the database.
router.post('/addblog',async(req,res)=>{const{title,tagline,slug,description}=req.body;letsaveBlog=awaitpool.query(`INSERT INTO blogs (title, tagline, slug, description) VALUES ('${title}', '${tagline}', '${slug}', '${description}')`);if(!saveBlog){res.status(404).json({status:404,message:'Some error occurred! Cannot save blog :('});}else{res.status(200).json({status:200,messaeg:'Your blogpost has been added successfully!'});}})Then the fourth api route will be to update a specific blog in the database.
router.put('/updateblog/:slug',async(req,res)=>{const{title,tagline,slug,description}=req.body;letsaveBlog=awaitpool.query(`UPDATE blogs SET title='${title}', tagline='${tagline}', slug='${slug}', description='${description}' WHERE slug='${req.params.slug}'`);if(!saveBlog){res.status(404).json({status:404,message:'Some error occurred! Cannot update blog :('});}else{res.status(200).json({status:200,messaeg:'Your blogpost has been updated successfully!'});}})Then the fourth api route will be to delete a specific blog from the database.
router.delete('/deleteblog/:slug',async(req,res)=>{letsaveBlog=awaitpool.query(`DELETE FROM blogs WHERE slug='${req.params.slug}'`);if(!saveBlog){res.status(404).json({status:404,message:'Some error occurred! Cannot delete blog :('});}else{res.status(200).json({status:200,messaeg:'Your blogpost has been deleted successfully!'});}})Then we will export the router module
module.exports=router;Create a "index.js" file to handle all the api routes.
Make the necessary imports
constexpress=require('express');constcors=require('cors');constapp=express();// initialization of express with appconstport=5000;Then write these two lines of code
app.use(cors());// enable cross origin requestsapp.use(express.json());// use default json body parser to parse the data.Use the api routes
app.use('/api/blogs',require('./routes/blog'))Create a custom 404 message
app.use((req,res,next)=>{res.status(404).json({status:404,message:'No such route was found! Please go to /api/blogs.'});})Listen on the given port
app.listen(port,()=>{console.log(`RestAPI listening on http://localhost:${port}`)})Yay! You have successfully created your rest api.
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