How to Use Prisma with Express: Simple Setup and Example

To use Prisma with Express, first install Prisma and set up your database schema. Then, create a Prisma client instance and use it inside your Express route handlers to query or modify your database asynchronously.

Syntax

Here is the basic syntax to use Prisma with Express:

• Import PrismaClient from @prisma/client.
• Create a new Prisma client instance.
• Use async functions in Express routes to call Prisma methods.
• Send the query results as responses.

javascript

import express from 'express';
import { PrismaClient } from '@prisma/client';

const app = express();
const prisma = new PrismaClient();

app.get('/items', async (req, res) => {
  const items = await prisma.item.findMany();
  res.json(items);
});

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

Example

This example shows a simple Express server using Prisma to fetch all records from an item table in the database. It demonstrates how to initialize Prisma, define a route, and send JSON data back to the client.

javascript

import express from 'express';
import { PrismaClient } from '@prisma/client';

const app = express();
const prisma = new PrismaClient();

app.get('/items', async (req, res) => {
  try {
    const items = await prisma.item.findMany();
    res.json(items);
  } catch (error) {
    res.status(500).json({ error: 'Failed to fetch items' });
  }
});

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

Output

Server running on http://localhost:3000

// When visiting http://localhost:3000/items, JSON array of items is returned

Common Pitfalls

Common mistakes when using Prisma with Express include:

• Not awaiting Prisma calls, causing unresolved promises.
• Not handling errors inside async route handlers.
• Forgetting to instantiate PrismaClient once and reusing it.
• Not running prisma generate after schema changes.

Always use async/await and try-catch blocks to handle database calls safely.

javascript

/* Wrong way: Missing await and error handling */
app.get('/items', (req, res) => {
  const items = prisma.item.findMany(); // Missing await
  res.json(items); // Sends a Promise, not data
});

/* Right way: Using async/await and try-catch */
app.get('/items', async (req, res) => {
  try {
    const items = await prisma.item.findMany();
    res.json(items);
  } catch (error) {
    res.status(500).json({ error: 'Failed to fetch items' });
  }
});

Quick Reference

Tips for using Prisma with Express:

• Install Prisma with npm install @prisma/client and npm install prisma --save-dev.
• Run npx prisma init to set up Prisma.
• Define your database schema in prisma/schema.prisma.
• Run npx prisma generate after schema changes.
• Use one PrismaClient instance per app to avoid connection issues.
• Always use async/await and handle errors in routes.

Key Takeaways

Create a single PrismaClient instance and reuse it in Express routes.

Use async/await with try-catch to handle database calls safely.

Run prisma generate after changing your schema to update the client.

Always await Prisma queries to get actual data, not promises.

Handle errors gracefully to avoid crashing your Express server.