Running an Express GraphQL Server | GraphQL

The simplest way to run a GraphQL API server is to use Express, a popular web application framework for Node.js. You will need to install two additional dependencies:

npm install express express
-
graphql graphql 
--
save

Let’s modify our “hello world” example so that it’s an API server rather than a script that runs a single query. We can use the ‘express’ module to run a webserver, and instead of executing a query directly with the graphql function, we can use the express-graphql library to mount a GraphQL API server on the “/graphql” HTTP endpoint:

var
 express 
=
 
require
(
"express"
)
var
 
{
 graphqlHTTP 
}
 
=
 
require
(
"express-graphql"
)
var
 
{
 buildSchema 
}
 
=
 
require
(
"graphql"
)

var
 schema 
=
 
buildSchema
(
`
  type Query {
    hello: String
  }
`
)

var
 root 
=
 
{
  hello
:
 
(
)
 
=
>
 
{
    
return
 
"Hello world!"
  
}
,
}

var
 app 
=
 
express
(
)
app
.
use
(
  
"/graphql"
,
  
graphqlHTTP
(
{
    schema
:
 schema
,
    rootValue
:
 root
,
    graphiql
:
 
true
,
  
}
)
)
app
.
listen
(
4000
)
console
.
log
(
"Running a GraphQL API server at http://localhost:4000/graphql"
)

You can run this GraphQL server with:

node server
.
js

Since we configured graphqlHTTP with graphiql: true, you can use the GraphiQL tool to manually issue GraphQL queries. If you navigate in a web browser to http://localhost:4000/graphql, you should see an interface that lets you enter queries. It should look like:

This screen shot shows the GraphQL query { hello } being issued and giving a result of { data: { hello: 'Hello world!' } }. GraphiQL is a great tool for debugging and inspecting a server, so we recommend running it whenever your application is in development mode.

At this point you have learned how to run a GraphQL server and how to use GraphiQL interface to issue queries. The next step is to learn how to issue GraphQL queries from client code.