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/gelscd gelsyarntsc -wnodemon 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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