swagger-json-schema-validator.js

// there are many json-schema validators available, I prefer ajv
let Ajv = require('ajv')
let ajv = Ajv({ allErrors:true })
let swagger = require('./docs/my-swagger-definition')

// validation middleware
let validateSchema = (parameters) => {
  return (req, res, next) => {
    let errors = []
    parameters.map(param => {
      let valid = ajv.validate(parameters[param].schema, req.body[param])
      if (!valid) {
        errors.push(ajv.errors)
      }
    })
    if (errors.length) return res.send(errors)
    next()
  }
}

app.post('/pets', validateSchema(swagger.paths['/pets'].post.parameters), (req, res) => {
  // parameters are valid; code can interact with database
  // ! you must still protect from SQL injection !
  res.send(req.body).status(201).end()
})

What if I want to write this middleware for all the routes. How would it work for a route like /pets/{petId} ?

The incoming request would have a value in place of petId eg. /pets/12 which would not match any paths from swagger file.