409 Conflict

Your request conflicts with the current server state. E.g., trying to register a username that is already taken.

When and Why to Use It

Use this for business logic conflicts. The most common example is trying to register a new account with an email address that is already in use.

Usage Examples

Shokupan (Functional)

import { HttpException, post } from 'shokupan';

export const registerUser = post('/register', async (req) => {
    const existing = await db.users.findByEmail(req.body.email);

    if (existing) {
        throw new HttpException('Email already registered', 409);
    }

    // ... create user
});

Shokupan (Controller)

import { Controller, Post, Body, HttpException } from 'shokupan';

@Controller('/api')
export class AuthController {
    @Post('/register')
    async registerUser(@Body() body: any) {
        const existing = await db.users.findByEmail(body.email);

        if (existing) {
            throw new HttpException('Email already registered', 409);
        }

        // ... create user
    }
}

Express

import express from 'express';
const app = express();

app.post('/register', async (req, res) => {
    const existing = await db.users.findByEmail(req.body.email);

    if (existing) {
        return res.status(409).json({ error: 'Email already registered' });
    }

    // ... create user
});

Nest

import { Controller, Post, Body, ConflictException } from '@nestjs/common';

@Controller('auth')
export class AuthController {
  @Post('register')
  async registerUser(@Body() body: any) {
    const existing = await db.users.findByEmail(body.email);

    if (existing) {
      throw new ConflictException('Email already registered');
    }

    // ... create user
  }
}

Koa

import Koa from 'koa';
const app = new Koa();

app.use(async ctx => {
  if (ctx.path === '/register' && ctx.method === 'POST') {
    const existing = await db.users.findByEmail(ctx.request.body.email);

    if (existing) {
      ctx.status = 409;
      ctx.body = { error: 'Email already registered' };
      return;
    }

    // ... create user
  }
});