NextJS Templates
Invoicing App Tutorial with Next.js, Vercel & Back4app

26min
In this tutorial, we will build a complete Invoicing App using Next.js as the frontend, Back4App as the backend, and additional services like Clerk for authentication, Stripe for payments, and Resend for email notifications. This guide will walk through setting up authentication, invoice management, payment processing, and deployment on Vercel.
1. Prerequisites
Before starting, ensure you have the following:
A Back4App account (Sign up here)
A Clerk account (Clerk.io) for authentication
A Stripe account (Stripe.com) for payment processing
A Resend account (Resend.io) for email notifications
Node.js and npm installed (Node.js Installation)
2. Setting Up the Backend (Back4App)
2.1 Create a New Project in Back4App
Log in to Back4App and create a new project.
Navigate to the Data Browser and create the following classes:
2.2 Data Models (Classes)
2.2.1 User (Automatically handled by Clerk)
objectId
username
email
2.2.2 Organization
Create a class called Organization.
Add the following columns:
name (String): The name of the organization.
ownerId (Pointer<_User>): Points to the User class (created automatically by Clerk).
members (Array<Pointer<_User>>): An array of users who belong to this organization.
2.2.3 Customer
Create a class called Customer.
Add these columns:
name (String): Customer's name.
email (String): Customer's email.
organizationId (Pointer): Organization to which this customer belongs.
2.2.4 Invoice
Create a class called Invoice.
Add these columns:
invoiceNumber (String): Unique invoice identifier.
customerId (Pointer): Links to the customer.
organizationId (Pointer): Links to the organization.
amount (Number): Total amount for the invoice.
status (String): Options include 'draft', 'sent', 'paid', and 'overdue'.
dueDate (Date): The invoice due date.
items (Array): The list of items in the invoice.
2.2.5 Payment
Create a class called Payment.
Add these columns:
invoiceId (Pointer): Links to the related invoice.
amount (Number): Payment amount.
stripeSessionId (String): The ID of the Stripe session.
status (String): Payment status (e.g., 'pending', 'successful', 'failed').
3. Setting Up the Frontend (Next.js)
3.1 Create a Next.js Project
Start by setting up your Next.js project with TypeScript, Tailwind CSS, and shadcn/ui components.
Bash
npx create-next-app@latest invoicing-app --typescript
cd invoicing-app
npm install tailwindcss postcss autoprefixer
npx tailwindcss init
npx create-next-app@latest invoicing-app --typescript
cd invoicing-app
npm install tailwindcss postcss autoprefixer
npx tailwindcss init
﻿
3.2 Set Up Tailwind CSS
Configure Tailwind by updating the tailwind.config.js and adding the styles to globals.css.
In tailwind.config.js:
JS
module.exports = {
  content: [
    './pages/**/*.{js,ts,jsx,tsx}',
    './components/**/*.{js,ts,jsx,tsx}',
  ],
  theme: {
    extend: {},
  },
  plugins: [],
};
module.exports = {
  content: [
    './pages/**/*.{js,ts,jsx,tsx}',
    './components/**/*.{js,ts,jsx,tsx}',
  ],
  theme: {
    extend: {},
  },
  plugins: [],
};
﻿
In styles/globals.css:
CSS
@tailwind base;
@tailwind components;
@tailwind utilities;
@tailwind base;
@tailwind components;
@tailwind utilities;
﻿
3.3 Install Parse SDK and Additional Services
Install the necessary dependencies for Parse, Clerk, Stripe, and Resend.
Bash
npm install parse @clerk/clerk-next stripe resend
npm install parse @clerk/clerk-next stripe resend
﻿
3.4 Initialize Parse SDK in Next.js
In pages/_app.tsx, initialize the Parse SDK with your Back4App credentials:
TypeScript
import { ClerkProvider } from '@clerk/clerk-react';
import Parse from 'parse';

Parse.initialize('YOUR_APP_ID', 'YOUR_JAVASCRIPT_KEY');
Parse.serverURL = 'https://parseapi.back4app.com';

function MyApp({ Component, pageProps }) {
  return (
    <ClerkProvider>
      <Component {...pageProps} />
    </ClerkProvider>
  );
}

export default MyApp;
import { ClerkProvider } from '@clerk/clerk-react';
import Parse from 'parse';

Parse.initialize('YOUR_APP_ID', 'YOUR_JAVASCRIPT_KEY');
Parse.serverURL = 'https://parseapi.back4app.com';

function MyApp({ Component, pageProps }) {
  return (
    <ClerkProvider>
      <Component {...pageProps} />
    </ClerkProvider>
  );
}

export default MyApp;
﻿
Replace 'YOUR_APP_ID' and 'YOUR_JAVASCRIPT_KEY' with your Back4App credentials.
4. Implementing User Authentication
4.1 Clerk Integration for Authentication
Set up Clerk for authentication. Go to Clerk's dashboard, create an application, and grab your API keys. Update your .env.local file with Clerk keys.
Bash
NEXT_PUBLIC_CLERK_FRONTEND_API=your-clerk-frontend-api
CLERK_API_KEY=your-clerk-api-key
NEXT_PUBLIC_CLERK_FRONTEND_API=your-clerk-frontend-api
CLERK_API_KEY=your-clerk-api-key
﻿
Now create pages/sign-in.tsx and pages/sign-up.tsx for sign-in and sign-up functionality using Clerk components.
In pages/sign-in.tsx:
Text
import { SignIn } from '@clerk/clerk-react';

export default function SignInPage() {
  return <SignIn />;
}
import { SignIn } from '@clerk/clerk-react';

export default function SignInPage() {
  return <SignIn />;
}
﻿
In pages/sign-up.tsx:
Text
import { SignUp } from '@clerk/clerk-react';

export default function SignUpPage() {
  return <SignUp />;
}
import { SignUp } from '@clerk/clerk-react';

export default function SignUpPage() {
  return <SignUp />;
}
﻿
5. Organization and Customer Management
5.1 Create Organizations
Users can create organizations that they own. Create a page pages/organizations/new.tsx for creating new organizations.
Text
import { useState } from 'react';
import Parse from 'parse';

export default function NewOrganization() {
  const [name, setName] = useState('');

  const handleCreateOrganization = async () => {
    const Organization = Parse.Object.extend('Organization');
    const organization = new Organization();
    organization.set('name', name);
    organization.set('ownerId', Parse.User.current());

    try {
      await organization.save();
      alert('Organization created successfully!');
    } catch (error) {
      console.error('Error creating organization:', error);
    }
  };

  return (
    <div>
      <h1>Create New Organization</h1>
      <input
        type="text"
        value={name}
        onChange={(e) => setName(e.target.value)}
        placeholder="Organization Name"
      />
      <button onClick={handleCreateOrganization}>Create</button>
    </div>
  );
}
import { useState } from 'react';
import Parse from 'parse';

export default function NewOrganization() {
  const [name, setName] = useState('');

  const handleCreateOrganization = async () => {
    const Organization = Parse.Object.extend('Organization');
    const organization = new Organization();
    organization.set('name', name);
    organization.set('ownerId', Parse.User.current());

    try {
      await organization.save();
      alert('Organization created successfully!');
    } catch (error) {
      console.error('Error creating organization:', error);
    }
  };

  return (
    <div>
      <h1>Create New Organization</h1>
      <input
        type="text"
        value={name}
        onChange={(e) => setName(e.target.value)}
        placeholder="Organization Name"
      />
      <button onClick={handleCreateOrganization}>Create</button>
    </div>
  );
}
﻿
5.2 Managing Customers
Create a customer management page pages/customers/new.tsx for adding new customers.
Text
import { useState } from 'react';
import Parse from 'parse';

export default function NewCustomer() {
  const [name, setName] = useState('');
  const [email, setEmail] = useState('');

  const handleCreateCustomer = async () => {
    const Customer = Parse.Object.extend('Customer');
    const customer = new Customer();
    customer.set('name', name);
    customer.set('email', email);
    customer.set('organizationId', Parse.User.current().get('organizationId'));

    try {
      await customer.save();
      alert('Customer created successfully!');
    } catch (error) {
      console.error('Error creating customer:', error);
    }
  };

  return (
    <div>
      <h1>Create New Customer</h1>
      <input
        type="text"
        value={name}
        onChange={(e) => setName(e.target.value)}
        placeholder="Customer Name"
      />
      <input
        type="email"
        value={email}
        onChange={(e) => setEmail(e.target.value)}
        placeholder="Customer Email"
      />
      <button onClick={handleCreateCustomer}>Create</button>
    </div>
  );
}
import { useState } from 'react';
import Parse from 'parse';

export default function NewCustomer() {
  const [name, setName] = useState('');
  const [email, setEmail] = useState('');

  const handleCreateCustomer = async () => {
    const Customer = Parse.Object.extend('Customer');
    const customer = new Customer();
    customer.set('name', name);
    customer.set('email', email);
    customer.set('organizationId', Parse.User.current().get('organizationId'));

    try {
      await customer.save();
      alert('Customer created successfully!');
    } catch (error) {
      console.error('Error creating customer:', error);
    }
  };

  return (
    <div>
      <h1>Create New Customer</h1>
      <input
        type="text"
        value={name}
        onChange={(e) => setName(e.target.value)}
        placeholder="Customer Name"
      />
      <input
        type="email"
        value={email}
        onChange={(e) => setEmail(e.target.value)}
        placeholder="Customer Email"
      />
      <button onClick={handleCreateCustomer}>Create</button>
    </div>
  );
}
﻿
6. Invoice Management
6.1 Create Invoices
Create an invoice creation page pages/invoices/new.tsx for generating new invoices.
Text
import { useState } from 'react';
import Parse from 'parse';

export default function NewInvoice() {
  const [invoiceNumber, setInvoiceNumber] = useState('');
  const [amount, setAmount] = useState(0);

  const handleCreateInvoice = async () => {
    const Invoice = Parse.Object.extend('Invoice');
    const invoice = new Invoice();
    invoice.set('invoiceNumber', invoiceNumber);
    invoice.set('amount', amount);
    invoice.set('organizationId', Parse.User.current().get('organizationId'));

    try {
      await invoice

.save();
      alert('Invoice created successfully!');
    } catch (error) {
      console.error('Error creating invoice:', error);
    }
  };

  return (
    <div>
      <h1>Create New Invoice</h1>
      <input
        type="text"
        value={invoiceNumber}
        onChange={(e) => setInvoiceNumber(e.target.value)}
        placeholder="Invoice Number"
      />
      <input
        type="number"
        value={amount}
        onChange={(e) => setAmount(parseFloat(e.target.value))}
        placeholder="Amount"
      />
      <button onClick={handleCreateInvoice}>Create</button>
    </div>
  );
}
import { useState } from 'react';
import Parse from 'parse';

export default function NewInvoice() {
  const [invoiceNumber, setInvoiceNumber] = useState('');
  const [amount, setAmount] = useState(0);

  const handleCreateInvoice = async () => {
    const Invoice = Parse.Object.extend('Invoice');
    const invoice = new Invoice();
    invoice.set('invoiceNumber', invoiceNumber);
    invoice.set('amount', amount);
    invoice.set('organizationId', Parse.User.current().get('organizationId'));

    try {
      await invoice

.save();
      alert('Invoice created successfully!');
    } catch (error) {
      console.error('Error creating invoice:', error);
    }
  };

  return (
    <div>
      <h1>Create New Invoice</h1>
      <input
        type="text"
        value={invoiceNumber}
        onChange={(e) => setInvoiceNumber(e.target.value)}
        placeholder="Invoice Number"
      />
      <input
        type="number"
        value={amount}
        onChange={(e) => setAmount(parseFloat(e.target.value))}
        placeholder="Amount"
      />
      <button onClick={handleCreateInvoice}>Create</button>
    </div>
  );
}
﻿
6.2 Viewing Invoices
Create a page pages/invoices/index.tsx to view all invoices with sorting and filtering options.
Text
import { useEffect, useState } from 'react';
import Parse from 'parse';

export default function InvoicesList() {
  const [invoices, setInvoices] = useState([]);

  useEffect(() => {
    const fetchInvoices = async () => {
      const Invoice = Parse.Object.extend('Invoice');
      const query = new Parse.Query(Invoice);
      const results = await query.find();
      setInvoices(results);
    };
    fetchInvoices();
  }, []);

  return (
    <div>
      <h1>Invoices</h1>
      {invoices.map(invoice => (
        <div key={invoice.id}>
          <h2>Invoice #{invoice.get('invoiceNumber')}</h2>
          <p>Amount: ${invoice.get('amount')}</p>
          <p>Status: {invoice.get('status')}</p>
        </div>
      ))}
    </div>
  );
}
import { useEffect, useState } from 'react';
import Parse from 'parse';

export default function InvoicesList() {
  const [invoices, setInvoices] = useState([]);

  useEffect(() => {
    const fetchInvoices = async () => {
      const Invoice = Parse.Object.extend('Invoice');
      const query = new Parse.Query(Invoice);
      const results = await query.find();
      setInvoices(results);
    };
    fetchInvoices();
  }, []);

  return (
    <div>
      <h1>Invoices</h1>
      {invoices.map(invoice => (
        <div key={invoice.id}>
          <h2>Invoice #{invoice.get('invoiceNumber')}</h2>
          <p>Amount: ${invoice.get('amount')}</p>
          <p>Status: {invoice.get('status')}</p>
        </div>
      ))}
    </div>
  );
}
﻿
7. Payment Processing (Stripe Integration)
7.1 Set Up Stripe Checkout
To process payments, integrate Stripe. In pages/invoices/[id].tsx, implement the payment link creation using Stripe Checkout.
Text
import { useRouter } from 'next/router';
import { useEffect, useState } from 'react';
import Stripe from 'stripe';

export default function InvoiceDetail() {
  const router = useRouter();
  const { id } = router.query;
  const [invoice, setInvoice] = useState(null);

  useEffect(() => {
    if (!id) return;
    const fetchInvoice = async () => {
      const Invoice = Parse.Object.extend('Invoice');
      const query = new Parse.Query(Invoice);
      query.equalTo('objectId', id);
      const result = await query.first();
      setInvoice(result);
    };
    fetchInvoice();
  }, [id]);

  const handlePayInvoice = async () => {
    const stripe = new Stripe(process.env.STRIPE_SECRET_KEY);
    const session = await stripe.checkout.sessions.create({
      payment_method_types: ['card'],
      line_items: [
        {
          price_data: {
            currency: 'usd',
            product_data: { name: `Invoice #${invoice.get('invoiceNumber')}` },
            unit_amount: invoice.get('amount') * 100,
          },
          quantity: 1,
        },
      ],
      mode: 'payment',
      success_url: window.location.origin + '/success',
      cancel_url: window.location.origin + '/cancel',
    });
    window.location.href = session.url;
  };

  if (!invoice) return <div>Loading...</div>;

  return (
    <div>
      <h1>Invoice #{invoice.get('invoiceNumber')}</h1>
      <p>Amount: ${invoice.get('amount')}</p>
      <button onClick={handlePayInvoice}>Pay Now</button>
    </div>
  );
}
import { useRouter } from 'next/router';
import { useEffect, useState } from 'react';
import Stripe from 'stripe';

export default function InvoiceDetail() {
  const router = useRouter();
  const { id } = router.query;
  const [invoice, setInvoice] = useState(null);

  useEffect(() => {
    if (!id) return;
    const fetchInvoice = async () => {
      const Invoice = Parse.Object.extend('Invoice');
      const query = new Parse.Query(Invoice);
      query.equalTo('objectId', id);
      const result = await query.first();
      setInvoice(result);
    };
    fetchInvoice();
  }, [id]);

  const handlePayInvoice = async () => {
    const stripe = new Stripe(process.env.STRIPE_SECRET_KEY);
    const session = await stripe.checkout.sessions.create({
      payment_method_types: ['card'],
      line_items: [
        {
          price_data: {
            currency: 'usd',
            product_data: { name: `Invoice #${invoice.get('invoiceNumber')}` },
            unit_amount: invoice.get('amount') * 100,
          },
          quantity: 1,
        },
      ],
      mode: 'payment',
      success_url: window.location.origin + '/success',
      cancel_url: window.location.origin + '/cancel',
    });
    window.location.href = session.url;
  };

  if (!invoice) return <div>Loading...</div>;

  return (
    <div>
      <h1>Invoice #{invoice.get('invoiceNumber')}</h1>
      <p>Amount: ${invoice.get('amount')}</p>
      <button onClick={handlePayInvoice}>Pay Now</button>
    </div>
  );
}
﻿
8. Email Notifications (Resend Integration)
8.1 Sending Invoice Emails
Set up Resend to send invoice emails to clients.
Text
import { Resend } from 'resend';

export default async function sendInvoiceEmail(invoiceId) {
  const resend = new Resend(process.env.RESEND_API_KEY);
  const invoice = await fetchInvoiceDetails(invoiceId); // Function to fetch invoice details
  const customer = await fetchCustomerDetails(invoice.customerId);

  await resend.sendEmail({
    from: '[email protected]',
    to: customer.email,
    subject: `Invoice #${invoice.invoiceNumber}`,
    html: `<h1>Invoice #${invoice.invoiceNumber}</h1><p>Amount: ${invoice.amount}</p>`,
  });
}
import { Resend } from 'resend';

export default async function sendInvoiceEmail(invoiceId) {
  const resend = new Resend(process.env.RESEND_API_KEY);
  const invoice = await fetchInvoiceDetails(invoiceId); // Function to fetch invoice details
  const customer = await fetchCustomerDetails(invoice.customerId);

  await resend.sendEmail({
    from: 'no-reply@invoicingapp.com',
    to: customer.email,
    subject: `Invoice #${invoice.invoiceNumber}`,
    html: `<h1>Invoice #${invoice.invoiceNumber}</h1><p>Amount: ${invoice.amount}</p>`,
  });
}
﻿
9. Deployment on Vercel
To deploy the app on Vercel, install the Vercel CLI and deploy.
Bash
npm install -g vercel
vercel
npm install -g vercel
vercel
﻿
Configure environment variables for Clerk, Stripe, Resend, and Back4App in the Vercel dashboard before deployment.
10. Conclusion
In this tutorial, we built a complete Invoicing App with Next.js, integrated Back4App for the backend, Clerk for authentication, Stripe for payments, and Resend for email notifications. We covered user and organization management, invoice creation, payment processing, and deployment.
Updated 08 Oct 2024
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