Package Exports
- graphql-middleware
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Readme
graphql-middleware
All in one solution to manage middleware in your GraphQL projects.
Overview
GraphQL Middleware is a schema wrapper which allows you to manage additional functionality across multiple resolvers efficiently.
- Easiest way to handle GraphQL middleware: Intuitive, yet familiar API will get under your skin in a second.
- Powerful: Allows complete control over your resolvers (Before, After).
- Compatible: Works with any GraphQL Schema.
Install
yarn add graphql-middlewareUsage
import { applyMiddleware } from 'graphql-middleware'
import { makeExecutableSchema } from 'graphql-tools'
import { authMiddleware, metricsMiddleware } from './middlewares'
// Minimal example middleware (before & after)
const beepMiddleware = {
Query: {
hello: async (resolve, parent, args, context, info) => {
// You can you middlewares to override arguments
const argsWithDefault = { name: 'Bob', ...args }
const result = await resolve(parent, argsWithDefault, context, info)
// Or change the returned values of resolvers
return result.replace(/Trump/g, 'beep')
},
},
}
const typeDefs = `
type Query {
hello(name: String): String
}
`
const resolvers = {
Query: {
hello: (parent, { name }, context) => `Hello ${name ? name : 'world'}!`,
},
}
const schema = makeExecutableSchema({ typeDefs, resolvers })
const schemaWithMiddleware = applyMiddleware(
schema,
metricsMiddleware,
authMiddleware,
beepMiddleware,
)Usage with graphql-yoga
graphql-yogahas built-in support forgraphql-middleware!
import { GraphQLServer } from 'graphql-yoga'
import { authMiddleware, metricsMiddleware } from './middlewares'
const typeDefs = `
type Query {
hello(name: String): String
}
`
const resolvers = {
Query: {
hello: (parent, { name }, context) => `Hello ${name ? name : 'world'}!`,
},
}
const server = new GraphQLServer({
typeDefs,
resolvers,
fieldMiddleware: [authMiddleware, metricsMiddleware],
documentMiddleware: [],
})
server.start(() => console.log('Server is running on localhost:4000'))Examples
API
A middleware is a resolver function that wraps another resolver function.
type IMiddlewareFunction = (
resolve: Function,
parent: any,
args: any,
context: any,
info: GraphQLResolveInfo,
) => Promise<any>
interface IMiddlewareTypeMap {
[key: string]: IMiddlewareFunction | IMiddlewareFieldMap
}
interface IMiddlewareFieldMap {
[key: string]: IMiddlewareFunction
}
type IMiddleware = IMiddlewareFunction | IMiddlewareTypeMap
function applyMiddleware(
schema: GraphQLSchema,
...middlewares: IMiddleware[]
): GraphQLSchemaGraphQL Middleware Use Cases
- Logging
- Metrics
- Input sanitisation
- Performance measurement
- Authorization
- Caching
- Tracing
FAQ
Can I use GraphQL Middleware without GraphQL Yoga?
Yes. Nevertheless, we encourage you to use it in combination with Yoga. Combining the power of fieldMiddleware that GraphQL Middleware offers, with documentMiddleware which Yoga exposes, gives you unparalleled control over the execution of your queries.
How does GraphQL Middleware compare to directives?
GraphQL Middleware and directives tackle the same problem in a completely different way. GraphQL Middleware allows you to implement all your middleware logic in your code, whereas directives encourage you to mix schema with your functionality.
Should I modify the context using GraphQL Middleware?
GraphQL Middleware allows you to modify the context of your resolvers, but we encourage you to use GraphQL Yoga's documentMiddleware for this functionality instead.
Help & Community 
Join our Slack community if you run into issues or have questions. We love talking to you!
