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This is the part 2 of post Intro to Nodejs - part 1.
\nIn this, we will continue from the express application we created and build a very simple Auth system.
\nWhat we need is a method to Login, a method to Signup and a method which returns us a list of students. We should only get the list of students if the user is authenticated / logged in.
\nSo lets go.
\nBefore we start, we need to know two things. GET and POST methods. GET and POST methods are used to transfer data from client to server in HTTP. The client can be a web app or a mobile app.
\nGET method is mainly for getting some data from the server. POST method is mainly for sending data to the server.
\nBefore login, we need to add students. To add students, we need to send data to server (student name, student email, password etc). that means we will create a POST request.
\nHere is what the post request handler would look like.
\napp.post('/signup', (req, res) => {\nconst body = req.body;\n\nconsole.log('req.body', body)\n\nconst email = body.email;\n\n// we need to check if email exists already or not\n\n// if email exists, throw error\n// otherwise\n// insert into database\n\n// Once saved to database, we will send response back to user with message ' User signup successfull'\n\n\n });We will write actual code after we set up MongoDB but first we’re trying to understand how it works. Lets say, our Signup feature has now been added, lets add a Login feature. Again in Login, data will be sent to server so again it will be a POST request.
\n app.post('/login', (req, res) => {\n console.log('req.body', body)\n\n const email = req.body.email;\n const password = req.body.password;\n\n// 1. find if a user exists with email\n// 2. if exists, check if password matches\n// 3. if password matches, Success. (in case of success, we should create and send a token(jwt token))\n// 4. otherwise, send error\n\n });So, now we know we just need to create these methods, so lets head over to MongoDB
\nMongoDB is a nosql database. It is very different from sql databases such as mysql, postgresql, SQL Server etc.
\nBut still, mongodb has some similarities with sql databases.
\nMongoDB has collections instead of sql tables.
\n\n just this code added to the top and our database / mongoDB has been connected. It really is that simple. Okay, lets talk a little bit about our students. We can think of students as our Models (like th M in MVC). a student will have email, student_id, password, name at the very least. We represent this in a model. lets create that model using mongoose. we also need to add one more module. after this, add these line Now, we have set up the model and setup bodyParser middleware. Lets write an actual Signup POST method. We can use browser for GET requests but for POST requests we would have to use a client (mobile app or web app). There is an alternative. Using Postman. Install it. Okay, now lets run our Node.js app Lets test route localhost:3000/signup \n This is predictable because we wrote only POST method and not GET method. So how do we test POST method? using Postman. \n Once we click on SEND, we get a response. \n But something else also happened. Remember we added a console.log(‘req.body’, body) before sending the response. Here \n What happened here is our Node.js server was hit with a request for signup and the data we got was {\nname: ‘Alamgir’\n}. This means our flows are ready. now if we add other values then they will be added themselves. Once we get the full data, we can add that to the database after checking if it doesnot exist already. So, let update the code to save it to MongoDB. Now lets try again from postman \n press Save \n We see the data in cmder. But is the data actually saved in Database/MongoDB? lets take a look. Open Robo 3T. connect to localhost \n double click \n Congratulations! Your student has been saved to MongoDB. that wasn’t so hard right. So what have we done? We have inserted a student into mongoDB using a post request. Now, I wanna retrieve all students inside my database. For now, I have inserted 2 more using Postman. Okay, so to retrieve, we get to get data from the server (Node.js) so in order to do that, we need to write a GET request. This will return all the students in the database. \n that is excellent. So now that we have our students in the database, lets write a login method for them. What it would do is check by email if the user exists, if it exists, then it will check for password. For login, we have to send email and password to the server from (mobile/web/client) so again, it will be a POST request. here’s how the login method would look like for now if the email doesnot exists, the result will be null otherwise we will get the object. lets see alamgir@gmail.com doesnot exists so \n Okay, so lets try with an email that exists. \n When the email exists, we will get an object in result instead of null. Okay, so lets write an error in case the email doesnot exists. \n Lets see it in action \n Using the wrong credentials, we get error response (code : 401) \n const Student = mongoose.model('Student', {\n name: String,\n student_id: Number,\n email: String,\n password: String,\n date_added: Date\n });npm install body-parserconst bodyParser = require('body-parser');\nconst app = express();\nmongoose.connect('mongodb://localhost:27017/myfirstmongodb', {useNewUrlParser: true,useUnifiedTopology:true});\n\napp.use(bodyParser.json());\napp.use(bodyParser.urlencoded({\n extended: true\n})); app.post('/signup', async (req, res) => {\nconst body = req.body;\nconsole.log('req.body', body);\nres.send({\n message: 'Success'\n});\n\n });nodemon indexapp.post('/signup', async (req, res) => {\nconst body = req.body;\nconsole.log('req.body', body)\n try{\nconst student = new Student(body);\n\nconst result = await student.save();\nres.send({\n message: 'Student signup successful'\n});\n\n }\n catch(ex){\n console.log('ex',ex);\n res.send({message: 'Error'}).status(401);\n }app.get('/students', async (req, res) => {\n\n const allStudents = await Student.find();\n console.log('allStudents', allStudents);\n\n res.send(allStudents);\n}); app.post('/login', async (req, res) => {\n const body = req.body;\n console.log('req.body', body);\n\n const email = body.email;\n\n // lets check if email exists\n\n const result = await Student.findOne({\"email\": email});\n console.log('result', result);\n\n // 2. if exists, check if password matches\n\nres.send({\n result: result\n});\n\n }); app.post('/login', async (req, res) => {\n const body = req.body;\n console.log('req.body', body);\n\n const email = body.email;\n\n // lets check if email exists\n\n const result = await Student.findOne({\"email\": email});\n if(!result) // this means result is null\n {\n res.status(401).send({\n Error: 'This user doesnot exists. Please signup first'\n });\n }\n\n console.log('result', result);\n\n // 2. if exists, check if password matches\n\n\n });