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Graphql实战系列(下)

前情介绍
在《Graphql 实战系列(上)》中我们已经完成技术选型,并将 graphql 桥接到凝胶 gels 项目中,并动态手写了 schema,可以通过 http://localhost:5000/graphql 查看效果。这一节,我们根据数据库表来自动生成基本的查询与更新 schema,并能方便的扩展 schema,实现我们想来的业务逻辑。
设计思路
对象定义在 apollo-server 中是用字符串来做的,而 Query 与 Mutation 只能有一个,而我们的定义又会分散在多个文件中,因此只能先以一定的形式把它们存入数组中,在生成 schema 前一刻再组合。
业务逻辑模块模板设计:
const customDefs = {
textDefs: `
type ReviseResult {
id: Int
affectedRows: Int
status: Int
message: String
},
queryDefs: [],
mutationDefs: []
}

const customResolvers = {
Query: {
},
Mutation: {
}
}
export {customDefs, customResolvers}
schema 合并算法
let typeDefs = []
let dirGraphql = requireDir(‘../../graphql’) // 从手写 schema 业务模块目录读入文件
G.L.each(dirGraphql, (item, name) => {
if (item && item.customDefs && item.customResolvers) {
typeDefs.push(item.customDefs.textDefs || ”) // 合并文本对象定义
typeDefObj.query = typeDefObj.query.concat(item.customDefs.queryDefs || []) // 合并 Query
typeDefObj.mutation = typeDefObj.mutation.concat(item.customDefs.mutationDefs || []) // 合并 Matation
let {Query, Mutation, …Other} = item.customResolvers
Object.assign(resolvers.Query, Query) // 合并 resolvers.Query
Object.assign(resolvers.Mutation, Mutation) // 合并 resolvers.Mutation
Object.assign(resolvers, Other) // 合并其它 resolvers
}
})
// 将 query 与 matation 查询更新对象由自定义的数组转化成为文本形式
typeDefs.push(Object.entries(typeDefObj).reduce((total, cur) => {
return total += `
type ${G.tools.bigCamelCase(cur[0])} {
${cur[1].join(”)}
}
`
}, ”))
从数据库表动态生成 schema
自动生成内容:

一个表一个对象;
每个表有两个 Query,一是单条查询,二是列表查询;
三个 Mutation,一是新增,二是更新,三是删除;
关联表以上篇中的 Book 与 Author 为例,Book 中有 author_id,会生成一个 Author 对象;而 Author 表中会生成一个对象列表 [Book]

mysql 类型 => graphql 类型转化常量定义
定义一类型转换,不在定义中的默认为 String。
const TYPEFROMMYSQLTOGRAPHQL = {
int: ‘Int’,
smallint: ‘Int’,
tinyint: ‘Int’,
bigint: ‘Int’,
double: ‘Float’,
float: ‘Float’,
decimal: ‘Float’,
}
从数据库中读取数据表信息
let dao = new BaseDao()
let tables = await dao.querySql(‘select TABLE_NAME,TABLE_COMMENT from information_schema.`TABLES` ‘ +
‘ where TABLE_SCHEMA = ? and TABLE_TYPE = ? and substr(TABLE_NAME,1,2) <> ? order by ?’,
[G.CONFIGS.dbconfig.db_name, ‘BASE TABLE’, ‘t_’, ‘TABLE_NAME’])
从数据库中读取表字段信息
tables.data.forEach((table) => {
columnRs.push(dao.querySql(‘SELECT `COLUMNS`.COLUMN_NAME,`COLUMNS`.COLUMN_TYPE,`COLUMNS`.IS_NULLABLE,’ +
‘`COLUMNS`.CHARACTER_SET_NAME,`COLUMNS`.COLUMN_DEFAULT,`COLUMNS`.EXTRA,’ +
‘`COLUMNS`.COLUMN_KEY,`COLUMNS`.COLUMN_COMMENT,`STATISTICS`.TABLE_NAME,’ +
‘`STATISTICS`.INDEX_NAME,`STATISTICS`.SEQ_IN_INDEX,`STATISTICS`.NON_UNIQUE,’ +
‘`COLUMNS`.COLLATION_NAME ‘ +
‘FROM information_schema.`COLUMNS` ‘ +
‘LEFT JOIN information_schema.`STATISTICS` ON ‘ +
‘information_schema.`COLUMNS`.TABLE_NAME = `STATISTICS`.TABLE_NAME ‘ +
‘AND information_schema.`COLUMNS`.COLUMN_NAME = information_schema.`STATISTICS`.COLUMN_NAME ‘ +
‘AND information_schema.`STATISTICS`.table_schema = ? ‘ +
‘where information_schema.`COLUMNS`.TABLE_NAME = ? and `COLUMNS`.table_schema = ?’,
[G.CONFIGS.dbconfig.db_name, table.TABLE_NAME, G.CONFIGS.dbconfig.db_name]))
})
几个工具函数
取数据库表字段类型,去除圆括号与长度信息
getStartTillBracket(str: string) {
return str.indexOf(‘(‘) > -1 ? str.substr(0, str.indexOf(‘(‘)) : str
}
下划线分隔的表字段转化为 big camel-case
bigCamelCase(str: string) {
return str.split(‘_’).map((al) => {
if (al.length > 0) {
return al.substr(0, 1).toUpperCase() + al.substr(1).toLowerCase()
}
return al
}).join(”)
}
下划线分隔的表字段转化为 small camel-case
smallCamelCase(str: string) {
let strs = str.split(‘_’)
if (strs.length < 2) {
return str
} else {
let tail = strs.slice(1).map((al) => {
if (al.length > 0) {
return al.substr(0, 1).toUpperCase() + al.substr(1).toLowerCase()
}
return al
}).join(”)
return strs[0] + tail
}
}
字段是否以_id 结尾,是表关联的标志
不以_id 结尾,是正常字段, 判断是否为 null,处理必填
typeDefObj[table].unshift(`${col[‘COLUMN_NAME’]}: ${typeStr}${col[‘IS_NULLABLE’] === ‘NO’ ? ‘!’ : ”}\n`)
以_id 结尾,则需要处理关联关系
//Book 表以 author_id 关联单个 Author 实体
typeDefObj[table].unshift(`””” 关联的实体 ”””
${G.L.trimEnd(col[‘COLUMN_NAME’], ‘_id’)}: ${G.tools.bigCamelCase(G.L.trimEnd(col[‘COLUMN_NAME’], ‘_id’))}`)
resolvers[G.tools.bigCamelCase(table)] = {
[G.L.trimEnd(col[‘COLUMN_NAME’], ‘_id’)]: async (element) => {
let rs = await new BaseDao(G.L.trimEnd(col[‘COLUMN_NAME’], ‘_id’)).retrieve({id: element[col[‘COLUMN_NAME’]] })
return rs.data[0]
}
}
//Author 表关联 Book 列表
let fTable = G.L.trimEnd(col[‘COLUMN_NAME’], ‘_id’)
if (!typeDefObj[fTable]) {
typeDefObj[fTable] = []
}
if (typeDefObj[fTable].length >= 2)
typeDefObj[fTable].splice(typeDefObj[fTable].length – 2, 0, `””” 关联实体集合 ”””${table}s: [${G.tools.bigCamelCase(table)}]\n`)
else
typeDefObj[fTable].push(`${table}s: [${G.tools.bigCamelCase(table)}]\n`)
resolvers[G.tools.bigCamelCase(fTable)] = {
[`${table}s`]: async (element) => {
let rs = await new BaseDao(table).retrieve({[col[‘COLUMN_NAME’]]: element.id})
return rs.data
}
}
生成 Query 查询
单条查询
if (paramId.length > 0) {
typeDefObj[‘query’].push(`${G.tools.smallCamelCase(table)}(${paramId}!): ${G.tools.bigCamelCase(table)}\n`)
resolvers.Query[`${G.tools.smallCamelCase(table)}`] = async (_, { id}) => {
let rs = await new BaseDao(table).retrieve({id})
return rs.data[0]
}
} else {
G.logger.error(`Table [${table}] must have id field.`)
}
列表查询
let complex = table.endsWith(‘s’) ? (table.substr(0, table.length – 1) + ‘z’) : (table + ‘s’)
typeDefObj[‘query’].push(`${G.tools.smallCamelCase(complex)}(${paramStr.join(‘, ‘)}): [${G.tools.bigCamelCase(table)}]\n`)
resolvers.Query[`${G.tools.smallCamelCase(complex)}`] = async (_, args) => {
let rs = await new BaseDao(table).retrieve(args)
return rs.data
}
生成 Mutation 查询
typeDefObj[‘mutation’].push(`
create${G.tools.bigCamelCase(table)}(${paramForMutation.slice(1).join(‘, ‘)}):ReviseResult
update${G.tools.bigCamelCase(table)}(${paramForMutation.join(‘, ‘)}):ReviseResult
delete${G.tools.bigCamelCase(table)}(${paramId}!):ReviseResult
`)
resolvers.Mutation[`create${G.tools.bigCamelCase(table)}`] = async (_, args) => {
let rs = await new BaseDao(table).create(args)
return rs
}
resolvers.Mutation[`update${G.tools.bigCamelCase(table)}`] = async (_, args) => {
let rs = await new BaseDao(table).update(args)
return rs
}
resolvers.Mutation[`delete${G.tools.bigCamelCase(table)}`] = async (_, { id}) => {
let rs = await new BaseDao(table).delete({id})
return rs
}
项目地址
https://github.com/zhoutk/gels
使用方法
git clone https://github.com/zhoutk/gels
cd gels
yarn
tsc -w
nodemon dist/index.js
然后就可以用浏览器打开链接:http://localhost:5000/graphql 查看效果了。
小结
我只能把大概思路写出来,让大家有个整体的概念,若想很好的理解,得自己把项目跑起来,根据我提供的思想,慢慢的去理解。因为我在编写的过程中还是遇到了不少的难点,这块既要自动化,还要能方便的接受手动编写的 schema 模块,的确有点难度。

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