GraphQL 是一种针对 Graph（图状数据）进行查询特别有优势的 Query Language（查询语言）
文档：
一、一个简单的例子
文档：https://graphql.cn/graphql-js/
依赖
npm i --save graphql
示例
var { graphql, buildSchema } = require('graphql'); // 使用 GraphQL schema language 构建一个 schema var schema = buildSchema(` type Query { hello: String } `); // 根节点为每个 API 入口端点提供一个 resolver 函数 var root = { hello: () => { return 'Hello world!'; }, }; // 运行 GraphQL query '{ hello }' ，输出响应 graphql(schema, '{ hello }', root).then((response) => { console.log(response); });
二、整合Express提供API服务
依赖
npm i --save express express-graphql graphql cors axios
服务端 server.js
const express = require("express"); const cors = require("cors"); // 用来解决跨域问题 const { graphqlHTTP } = require("express-graphql"); const { buildSchema } = require("graphql"); // 创建 schema // 1. 感叹号 ！ 代表 not-null const schema = buildSchema(` type Query { username: String age: Int! } `); //定义服务端数据 const root = { username: () => { return "李华"; }, age: () => { return Math.ceil(Math.random() * 100); }, }; const app = express(); app.use(cors()); app.use("/graphql", graphqlHTTP({ schema: schema, rootValue: root, graphiql: true, // 启用GraphiQL }) ); app.listen(3300, ()=>{ console.log("Running a GraphQL API server at http://localhost:3300/graphql"); });
可视化地址：http://localhost:3300/graphql
客户端 client.js
const axios = require("axios"); let data = { query: '{username, age}' } axios.post("http://localhost:3300/graphql", data).then((res) => { console.log(res.data.data); }); // { username: '李华', age: 26 }
参考
三、看一个复杂一点的例子
用户User - 博客Blog - 地址Address 三者存在的一对一，一对多关系
服务端代码
var express = require("express"); var { graphqlHTTP } = require("express-graphql"); var { GraphQLSchema, GraphQLObjectType, GraphQLID, GraphQLString, GraphQLInt, GraphQLList, } = require("graphql"); // 博客 var Blog = new GraphQLObjectType({ name: "Blog", fields: { id: { type: GraphQLID }, title: { type: GraphQLString }, content: { type: GraphQLString }, created_time: { type: GraphQLInt }, }, }); // 地址 var Address = new GraphQLObjectType({ name: "Address", fields: { id: { type: GraphQLID }, name: { type: GraphQLString }, }, }); // 用户 User 一对一 Address, User 一对多 Blog var User = new GraphQLObjectType({ name: "User", fields: { id: { type: GraphQLID }, username: { type: GraphQLString }, password: { type: GraphQLString }, address: { type: Address, resolve(parent, args) { console.log(parent, args); return { id: parent.id, name: "name" + parent.id, }; }, }, blogs: { type: new GraphQLList(Blog), args: { limit: { type: GraphQLInt }, }, resolve(parent, args) { console.log(parent, args); let list = []; for (let i =0; i < args.limit; i++) { list.push({ id: i, title: "title" + i, content: "content" + i, created_time: i * 100, }); } return list; }, }, }, }); var Query = new GraphQLObjectType({ name: "Query", fields: { user: { type: User, args: { id: { type: GraphQLID }, }, resolve(parent, args) { console.log(parent, args); return { id: args.id, username: "admin" + args.id, password: "123456" + args.id, }; }, }, }, }); var schema = new GraphQLSchema({ query: Query, }); // express服务 var app = express(); app.use( "/graphql", graphqlHTTP({ schema: schema, graphiql: true, }) ); app.listen(4000, () => { console.log("server at: http://localhost:4000/graphql"); });
客户端请求
const axios = require("axios"); let query = ` { user(id: 3) { id username password blogs(limit: 2) { id title content created_time } address { id name } } } ` axios.post("http://localhost:4000/graphql", {query}).then((res) => { console.log(res.data.data); }); /** { user: { id: '3', username: 'admin3', password: '1234563', blogs: [ [Object], [Object] ], address: { id: '3', name: 'name3' } } } */
