Graphql

Graphql三大特性：

   1.首先，它是声明式的。查询的结果格式由请求方（即客户端）决定而非响应方（即服务器端）决定，也就是说，一个 GraphQL 查询结果的返回是同客户端请求时的结构一样的，不多不少，不增不减。

   2.其次，它是可组合的。一个 GraphQL 的查询结构是一个有层次的字段集，它可以任意层次地进行嵌套或组合，也就是说它可以通过对字段进行组合、嵌套来满足需求

   3.第三，它是强类型的。强类型保证，只有当一个 GraphQL 查询满足所设定的查询类型，那么查询的结果才会被执行。

适用场景：

     1.兼容多平台导致字段冗余

     2.一个页面需要多次调用 API 聚合数据

     3.需求经常改动导致接口很难为单一接口精简逻辑

gql

GraphQL 既是一种用于 API 的查询语言也是一个满足你数据查询的运行时。 GraphQL 对你的 API 中的数据提供了一套易于理解的完整描述，使得客户端能够准确地获得它需要的数据，而且没有任何冗余，也让 API 更容易地随着时间推移而演进，还能用于构建强大的开发者工具。

gql数据类型

1. GraphQLInt: 整数，对应 JavaScript 的 Number
2. GraphQLFloat: 浮点数，对应 JavaScript 的 Number
3. GraphQLString: 字符串，对应 JavaScript 的 String
4. GraphQLBoolean: 布尔值，对应 JavaScript 的 Boolean
5. GraphQLID: ID 值，是一个序列化后值唯一的字符串
6. GraphQLList: 数组
7. GraphQLObjectType: 对象
8. GraphQLNonNull: 强制类型的值不能为 null，并且在请求出错时一定会报错。可以用于必须保证值不能为 null 的字段
9. GraphQLUnionType: 联合类型用于描述某个字段能够支持的所有返回类型,即可能返回的类型有多重的情况下。

gql配置环境：

1.npm init 创建 package.json 文件 

package.json文件

{

"name": "gql",

"version": "1.0.0",

"description": "simple GraphQl server",

"main": "server.js",

"scripts": {

"dev:server": "nodemon server.js"

},

"author": "zhf",

"license": "ISC"

}

2.npm install express experss-graphql nodemon --save 安装模块

package.json文件

{ 
"name": "gql", 
"version": "1.0.0", 
"description": "simple GraphQl server", 
"main": "server.js", 
"scripts": 
{ "dev:server": "nodemon server.js" }, 
"author": "zhf", 
"license": "ISC", 
"dependencies": { "express": "^4.16.3", 
"express-graphql": "^0.6.12", 
"graphql": "^0.13.2", 
"nodemon": "^1.17.3" 
} 
}

新建server.js文件（导入模块）gql服务 运行服务命令：npm run dev:srever.js

server.js文件
const express = require('express');
const expressGraphQL = require('express-graphql');
const schema = require('./schema.js');
const app = express();

app.use('/graphql', expressGraphQL({
  schema: schema,
  graphiql: true
}));

app.listen(4000, () => {
  console.log('启动')
});

新建schema.js文件

schema.js文件
const {
  GraphQLObjectType,
  GraphQLString,
  GraphQLInt,
  GraphQLSchema,
  GraphQLList,
  GraphQLNonNull
} = require('graphql');
安装graphql：npm install graphql --save

在schema.js里面写假数据启动服务后通过任意字段查询数据：
const {
  GraphQLObjectType,
  GraphQLString,
  GraphQLInt,
  GraphQLSchema,
  GraphQLList,
  GraphQLNonNull
} = require('graphql');
// 假数据
const customers = [
  { id: '1', name: 'eee', email: '333', age: 10 },

  { id: '2', name: '222', email: '24r', age: 10 },
  { id: '3', name: '444', email: '44', age: 10 },
  { id: '4', name: '555', email: '336663', age: 10 },
]
// customer Type
const CustomerType = new GraphQLObjectType({
  name: 'Customer',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    email: { type: GraphQLString },
    age: { type: GraphQLInt },
  })
})
// Root Query
const RootQuery = new GraphQLObjectType({
  name: 'RootQueryType',
  fields: {
    customer: {
      type: CustomerType,
      args: {
        id: { type: GraphQLString }
      },
      resolve(parentValue, args) {
        for (let i = 0; i < customers.length; i++) {
          if (customers[i].id == args.id) {
            return customers[i];
          }
        }
      }
    }
  }
});
module.exports = new GraphQLSchema({
  query: RootQuery
});

访问：http://localhost:4000/graphql(通过id查询数据)

通过字段查询数据

const {
  GraphQLObjectType,
  GraphQLString,
  GraphQLInt,
  GraphQLSchema,
  GraphQLList,
  GraphQLNonNull
} = require('graphql');
// 假数据
const customers = [
  { id: '1', name: 'eee', email: '333', age: 10 },
  { id: '2', name: '222', email: '24r', age: 10 },
  { id: '3', name: '444', email: '44', age: 10 },
  { id: '4', name: '555', email: '336663', age: 10 },
]
// customer Type
const CustomerType = new GraphQLObjectType({
  name: 'Customer',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    email: { type: GraphQLString },
    age: { type: GraphQLInt },
  })
})
// Root Query
const RootQuery = new GraphQLObjectType({
  name: 'RootQueryType',
  fields: {
    customer: {
      type: CustomerType,
      args: {
        id: { type: GraphQLString }
      },
      resolve(parentValue, args) {
        for (let i = 0; i < customers.length; i++) {
          if (customers[i].id == args.id) {
            return customers[i];
          }
        }
      }
    },
    customers: {
      type: new GraphQLList(CustomerType),
      resolve(parentValue, args) {
        return customers;
      }
    }
  }
});
module.exports = new GraphQLSchema({
  query: RootQuery
});

访问：localhost:4000/graphql

建ison文件，对数据 增 删 改 查。

修改package.json

{
  "name": "gql",
  "version": "1.0.0",
  "description": "simple GraphQl server",
  "main": "server.js",
  "scripts": {
    "dev:server": "nodemon server.js",
    "json:server": "json-server --watch data.json"
  },
  "author": "zhf",
  "license": "ISC",
  "dependencies": {
    "express": "^4.16.3",
    "express-graphql": "^0.6.12",
    "graphql": "^0.13.2",
    "nodemon": "^1.17.3"
  }
}

新建data.json文件，假数据如下：

{
    "customers": [
        {
            "id": "1",
            "name": "aa",
            "email": "193838",
            "age": 2
        },
        {
            "id": "2",
            "name": "aa",
            "email": "193838",
            "age": 46
        },
        {
            "id": "3",
            "name": "aa",
            "email": "193838",
            "age": 5
        }
    ]
}

安装 npm install json-server axios --save 启动 npm run json:server.

http://localhost:3000

可访问全部假数据。

通过id查询数据

const axios = require('axios')
const {
  GraphQLObjectType,
  GraphQLString,
  GraphQLInt,
  GraphQLSchema,
  GraphQLList,
  GraphQLNonNull
} = require('graphql');
// 假数据
// const customers = [
//   { id: '1', name: 'eee', email: '333', age: 10 },
//   { id: '2', name: '222', email: '24r', age: 10 },
//   { id: '3', name: '444', email: '44', age: 10 },
//   { id: '4', name: '555', email: '336663', age: 10 },
// ]
// customer Type
const CustomerType = new GraphQLObjectType({
  name: 'Customer',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    email: { type: GraphQLString },
    age: { type: GraphQLInt },
  })
})
// Root Query
const RootQuery = new GraphQLObjectType({
  name: 'RootQueryType',
  fields: {
    customer: {
      type: CustomerType,
      args: {
        id: { type: GraphQLString }
      },
      resolve(parentValue, args) {
        // for (let i = 0; i < customers.length; i++) {
        //   if (customers[i].id == args.id) {
        //     return customers[i];
        //   }
        // }
        // 通过id查询
        return axios.get('http://localhost:3000/customers/'+ args.id)
        .then(res => res.data)
      }
    },
    customers: {
      type: new GraphQLList(CustomerType),
      resolve(parentValue, args) {
        return customers;
      }
    }
  }
});
module.exports = new GraphQLSchema({
  query: RootQuery
});

通过字段查询数据（可自定义字段）ps:想查几个查几个

const axios = require('axios')
const {
  GraphQLObjectType,
  GraphQLString,
  GraphQLInt,
  GraphQLSchema,
  GraphQLList,
  GraphQLNonNull
} = require('graphql');
// 假数据
// const customers = [
//   { id: '1', name: 'eee', email: '333', age: 10 },
//   { id: '2', name: '222', email: '24r', age: 10 },
//   { id: '3', name: '444', email: '44', age: 10 },
//   { id: '4', name: '555', email: '336663', age: 10 },
// ]
// customer Type
const CustomerType = new GraphQLObjectType({
  name: 'Customer',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    email: { type: GraphQLString },
    age: { type: GraphQLInt },
  })
})
// Root Query
const RootQuery = new GraphQLObjectType({
  name: 'RootQueryType',
  fields: {
    customer: {
      type: CustomerType,
      args: {
        id: { type: GraphQLString }
      },
      resolve(parentValue, args) {
        // for (let i = 0; i < customers.length; i++) {
        //   if (customers[i].id == args.id) {
        //     return customers[i];
        //   }
        // }
        // 通过id查询
        return axios.get('http://localhost:3000/customers/' + args.id)
          .then(res => res.data)
      }
    },
    customers: {
      type: new GraphQLList(CustomerType),
      // 通过字段查询
      resolve(parentValue, args) {
        return axios.get('http://localhost:3000/customers')
          .then(res => res.data)
      }
    }
  }
});
module.exports = new GraphQLSchema({
  query: RootQuery
});

// 通过·id查询
// {
//   customer(id:"1"){
//     name,
//     age
//   }
  
// }
// 通过字段查询
// {
//   customers {
//     name,
//     email,
//     age
//   }
// }

新增一条数据

const axios = require('axios')
const {
  GraphQLObjectType,
  GraphQLString,
  GraphQLInt,
  GraphQLSchema,
  GraphQLList,
  GraphQLNonNull
} = require('graphql');
// 假数据
// const customers = [
//   { id: '1', name: 'eee', email: '333', age: 10 },
//   { id: '2', name: '222', email: '24r', age: 10 },
//   { id: '3', name: '444', email: '44', age: 10 },
//   { id: '4', name: '555', email: '336663', age: 10 },
// ]
// customer Type
const CustomerType = new GraphQLObjectType({
  name: 'Customer',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    email: { type: GraphQLString },
    age: { type: GraphQLInt },
  })
})
// Root Query
const RootQuery = new GraphQLObjectType({
  name: 'RootQueryType',
  fields: {
    customer: {
      type: CustomerType,
      args: {
        id: { type: GraphQLString }
      },
      resolve(parentValue, args) {
        // for (let i = 0; i < customers.length; i++) {
        //   if (customers[i].id == args.id) {
        //     return customers[i];
        //   }
        // }
        // 通过id查询
        return axios.get('http://localhost:3000/customers/' + args.id)
          .then(res => res.data)
      }
    },
    customers: {
      type: new GraphQLList(CustomerType),
      // 通过字段查询
      resolve(parentValue, args) {
        return axios.get('http://localhost:3000/customers')
          .then(res => res.data)
      }
    }
  }
});
// Mutaion
// 新增数据
const mutation = new GraphQLObjectType({
  name: 'Mutation',
  fields: {
    addCustomer:{
      type: CustomerType,
      args:{
        name: {type: new GraphQLNonNull(GraphQLString)},
        email: {type: new GraphQLNonNull(GraphQLString)},
        age: {type: new GraphQLNonNull(GraphQLInt)}
      },
      resolve(parentValue, args){
        return axios.post('http://localhost:3000/customers', {
          name: args.name,
          email: args.email,
          age: args.age
        })
        .then(res => res.data)
      }
    }
  }
})
module.exports = new GraphQLSchema({
  query: RootQuery,
  mutation
});

// 通过·id查询
// {
//   customer(id:"1"){
//     name,
//     age
//   }
  
// }
// 通过字段查询
// {
//   customers {
//     name,
//     email,
//     age
//   }
// }
// 新增一条数据
// mutation{
//   addCustomer(name:"22",email:"22",age:12){
//     name,
//     email,
//     age
//   }
// }

通过id删除一条数据

const axios = require('axios')
const {
  GraphQLObjectType,
  GraphQLString,
  GraphQLInt,
  GraphQLSchema,
  GraphQLList,
  GraphQLNonNull
} = require('graphql');
// 假数据
// const customers = [
//   { id: '1', name: 'eee', email: '333', age: 10 },
//   { id: '2', name: '222', email: '24r', age: 10 },
//   { id: '3', name: '444', email: '44', age: 10 },
//   { id: '4', name: '555', email: '336663', age: 10 },
// ]
// customer Type
const CustomerType = new GraphQLObjectType({
  name: 'Customer',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    email: { type: GraphQLString },
    age: { type: GraphQLInt },
  })
})
// Root Query
const RootQuery = new GraphQLObjectType({
  name: 'RootQueryType',
  fields: {
    customer: {
      type: CustomerType,
      args: {
        id: { type: GraphQLString }
      },
      resolve(parentValue, args) {
        // for (let i = 0; i < customers.length; i++) {
        //   if (customers[i].id == args.id) {
        //     return customers[i];
        //   }
        // }
        // 通过id查询
        return axios.get('http://localhost:3000/customers/' + args.id)
          .then(res => res.data)
      }
    },
    customers: {
      type: new GraphQLList(CustomerType),
      // 通过字段查询
      resolve(parentValue, args) {
        return axios.get('http://localhost:3000/customers')
          .then(res => res.data)
      }
    }
  }
});
// Mutaion
// 新增数据
const mutation = new GraphQLObjectType({
  name: 'Mutation',
  fields: {
    addCustomer:{
      type: CustomerType,
      args:{
        name: {type: new GraphQLNonNull(GraphQLString)},
        email: {type: new GraphQLNonNull(GraphQLString)},
        age: {type: new GraphQLNonNull(GraphQLInt)}
      },
      resolve(parentValue, args){
        return axios.post('http://localhost:3000/customers', {
          name: args.name,
          email: args.email,
          age: args.age
        })
        .then(res => res.data)
      }
    },
    deleteCustomer:{
      type: CustomerType,
      args:{
        id:{type:new GraphQLNonNull(GraphQLString)}
      },
      resolve(parentValue, args){
        return axios.delete('http://localhost:3000/customers/'+args.id)
        .then(res => res.data)
      }
    }
  }
})
module.exports = new GraphQLSchema({
  query: RootQuery,
  mutation
});

// 通过·id查询
// {
//   customer(id:"1"){
//     name,
//     age
//   }
  
// }
// 通过字段查询
// {
//   customers {
//     name,
//     email,
//     age
//   }
// }
// 新增一条数据
// mutation{
//   addCustomer(name:"22",email:"22",age:12){
//     name,
//     email,
//     age
//   }
// }
// 删除数据
// mutation{
//   deleteCustomer(id:"1"){
//     id
//   }
// }

修改数据

const axios = require('axios')
const {
  GraphQLObjectType,
  GraphQLString,
  GraphQLInt,
  GraphQLSchema,
  GraphQLList,
  GraphQLNonNull
} = require('graphql');
// 假数据
// const customers = [
//   { id: '1', name: 'eee', email: '333', age: 10 },
//   { id: '2', name: '222', email: '24r', age: 10 },
//   { id: '3', name: '444', email: '44', age: 10 },
//   { id: '4', name: '555', email: '336663', age: 10 },
// ]
// customer Type
const CustomerType = new GraphQLObjectType({
  name: 'Customer',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    email: { type: GraphQLString },
    age: { type: GraphQLInt },
  })
})
// Root Query
const RootQuery = new GraphQLObjectType({
  name: 'RootQueryType',
  fields: {
    customer: {
      type: CustomerType,
      args: {
        id: { type: GraphQLString }
      },
      resolve(parentValue, args) {
        // for (let i = 0; i < customers.length; i++) {
        //   if (customers[i].id == args.id) {
        //     return customers[i];
        //   }
        // }
        // 通过id查询
        return axios.get('http://localhost:3000/customers/' + args.id)
          .then(res => res.data)
      }
    },
    customers: {
      type: new GraphQLList(CustomerType),
      // 通过字段查询
      resolve(parentValue, args) {
        return axios.get('http://localhost:3000/customers')
          .then(res => res.data)
      }
    }
  }
});
// Mutaion
// 新增数据
const mutation = new GraphQLObjectType({
  name: 'Mutation',
  fields: {
    addCustomer:{
      type: CustomerType,
      args:{
        name: {type: new GraphQLNonNull(GraphQLString)},
        email: {type: new GraphQLNonNull(GraphQLString)},
        age: {type: new GraphQLNonNull(GraphQLInt)}
      },
      resolve(parentValue, args){
        return axios.post('http://localhost:3000/customers', {
          name: args.name,
          email: args.email,
          age: args.age
        })
        .then(res => res.data)
      }
    },
    deleteCustomer:{
      type: CustomerType,
      args:{
        id:{type:new GraphQLNonNull(GraphQLString)}
      },
      resolve(parentValue, args){
        return axios.delete('http://localhost:3000/customers/'+args.id)
        .then(res => res.data)
      }
    },
    editCustomer:{
      type: CustomerType,
      args:{
        id: {type: new GraphQLNonNull(GraphQLString)},
        name:{type:GraphQLString},
        email: {type: GraphQLString},
        age: {type: GraphQLInt}
      },
      resolve(parentValue, args){
        return axios.patch('http://localhost:3000/customers/'+args.id,args)
        .then(res => res.data)
      }
    }
  }
})
module.exports = new GraphQLSchema({
  query: RootQuery,
  mutation
});

// 通过·id查询
// {
//   customer(id:"1"){
//     name,
//     age
//   }
  
// }
// 通过字段查询
// {
//   customers {
//     name,
//     email,
//     age
//   }
// }
// 新增一条数据
// mutation{
//   addCustomer(name:"22",email:"22",age:12){
//     name,
//     email,
//     age
//   }
// }
// 删除数据
// mutation{
//   deleteCustomer(id:"1"){
//     id
//   }
// }
// 修改数据
// mutation{
//   editCustomer(id:"2",name:"2"){
//     age,
//     name,
//     email
//   }
// }

启动服务：npm run dev:server     npm run json:server