运行 Express GraphQL 服务器

运行 GraphQL API 服务器的最简单方法是使用 Express，这是一种流行的 Node.js Web 应用框架。你将需要安装两个额外的依赖：

英：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 graphql-http graphql ruru --save

让我们修改“hello world”示例，使其成为 API 服务器而不是运行单个查询的脚本。我们可以使用 'express' 模块来运行 Web 服务器，而不是直接使用 graphql 函数执行查询，我们可以使用 graphql-http 库在“/graphql”HTTP 端点上挂载 GraphQL API 服务器：

英：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 graphql-http library to mount a GraphQL API server on the “/graphql” HTTP endpoint:

var express = require("express")
var { createHandler } = require("graphql-http/lib/use/express")
var { buildSchema } = require("graphql")
var { ruruHTML } = require("ruru/server")

// Construct a schema, using GraphQL schema language
var schema = buildSchema(`
  type Query {
    hello: String
  }
`)

// The root provides a resolver function for each API endpoint
var root = {
  hello: () => {
    return "Hello world!"
  },
}

var app = express()

// Create and use the GraphQL handler.
app.all(
  "/graphql",
  createHandler({
    schema: schema,
    rootValue: root,
  })
)

// Serve the GraphiQL IDE.
app.get("/", (_req, res) => {
  res.type("html")
  res.end(ruruHTML({ endpoint: "/graphql" }))
})

// Start the server at port
app.listen(4000)
console.log("Running a GraphQL API server at http://localhost:4000/graphql")

你可以使用以下命令运行此 GraphQL 服务器：

英：You can run this GraphQL server with:

node server.js

你可以使用 Graph_i_QL IDE 工具直接在浏览器中发出 GraphQL 查询。如果你导航到 http://localhost:4000，你应该会看到一个可让你输入查询的界面。

英：You can use the Graph_i_QL IDE tool to issue GraphQL queries directly in the browser. If you navigate to http://localhost:4000, you should see an interface that lets you enter queries.

至此，你已经学习了如何运行 GraphQL 服务器。下一步是学习如何 从客户端代码发出 GraphQL 查询。

英：At this point you have learned how to run a GraphQL server. The next step is to learn how to issue GraphQL queries from client code.