我目前正在学习Graphql(apollo)并使用Node.js作为后端。
我在查询和突变方面取得了一些进展，但我在订阅方面停滞不前。我看过几个视频，读过一些博客，但我很难掌握它，因为他们使用前端框架，如react，我不熟悉react或任何其他前端javascript框架。
我只对后端学习它感兴趣。
有谁能帮我做这件事吗?我有三个独立的查询(或不管他们叫什么)，我正在工作。用户,邮报》和评论
现在我想在有人添加新评论或创建新帖子时生成订阅。对于用户、评论和帖子，我已经有了添加、更新和删除的突变。
当前没有身份验证或授权。
你的问题更多的是为了帮助我实现这个，而不是实际上问一个问题或问题，你在尝试了一系列的顺序后遇到的一些步骤。
这可能有助于您学习和实现GraphQL订阅;
- https://www.apollographql.com/docs/apollo-server/data/subscriptions/
- https://www.youtube.com/watch?v=R2IrBI4-7Kg& t = 698年代
如果你已经尝试了一些东西，面对一堵墙，请添加你的代码和你所做的，所以我可以帮助你在哪里你错了，或者你可以做什么希望。欢呼。
我提供的解决方案是在@apollo/server v.4上精心制作的，expressMiddleware and mongodb/mongoose在后端，subscribeToMore与updateQuery在客户端，而不是useSubscription钩子。
不再支持graphql-transport-ws传输库;请使用graphql-ws。
的实现区分了三个主要集合:User、Post和Comment，以及订阅对于post creation,post modification和用户authentication，
同样，从12.2022开始，应用以下设置和配置。
后端订阅:
安装下列依赖项:
$ npm i @apollo/server @graphql-tools/schema graphql-subscriptions graphql-ws ws cors body-parser mongoose graphql express
我假设你已经配置了你的MongoDB模型;如果没有，你可能想看看这个repo的基本设置。
设置模式类型和解析器，如下所示。
// typeDefs.js
const typeDefs = `#graphql
type User {
id: ID!
email: String!
posts: [Post]!
commentsMade: [Comment]!
}
type Token {
value: String!
}
input UpdatePostInput {
title: String!
}
type Post {
id: ID!
title: String!
postedBy: User
comments: [Comment]!
}
input CommentInput {
text: String!
}
type Comment {
id: ID!
text: String!
commenter: User!
commentFor: Post!
}
type Query {
users: [User]!
user(id: ID!): User!
posts: [Post!]!
post(id: ID!): Post!
comment(id: ID!): Comment!
comments: [Comment!]!
}
type Mutation {
signup(email: String!, password: String!): User
signin(email: String!, password: String!): Token
createPost(title: String): Post
createComment(postId: String!, commentInput: CommentInput!): Comment
updatePost(postId: ID!, updatePostInput: UpdatePostInput!): Post
}
type Subscription {
postAdded: Post
commentAdded: Comment
postUpdated: Post
}
`
export default typeDefs
// resolvers.js
import dotenv from 'dotenv'
import { PubSub } from 'graphql-subscriptions'
import mongoose from 'mongoose'
import { GraphQLError } from 'graphql'
import bcrypt from 'bcrypt'
import UserModel from '../models/User.js'
import PostModel from '../models/Post.js'
import CommentModel from '../models/Comment.js'
dotenv.config()
...
const pubsub = new PubSub()
const User = UserModel
const Post = PostModel
const Comment = CommentModel
const secret = process.env.TOKEN_SECRET
const resolvers = {
Query: {...},
Mutation: {
...
createPost: async (_, args, contextValue) => {
const authUser = contextValue.authUser
if (!authUser) {
throw new GraphQLError('User is not authenticated', {
extensions: {
code: 'UNAUTHENTICATED',
http: { status: 401 },
},
})
}
const post = new Post({
...args,
postedBy: mongoose.Types.ObjectId(authUser.id),
})
try {
const savedPost = await post.save()
authUser.posts = authUser.posts.concat(post._id)
await authUser.save()
const addedPost = {
id: savedPost.id,
title: savedPost.title,
postedBy: savedPost.postedBy,
comments: savedPost.comments,
}
// subscription postAdded with object iterator POST_ADDED
pubsub.publish('POST_ADDED', { postAdded: addedPost })
return post
} catch (error) {
throw new GraphQLError(`Error: ${error.message}`, {
extensions: {
code: 'BAD_USER_INPUT',
http: { status: 400 },
argumentName: args,
},
})
}
},
updatePost: async (_, args, contextValue) => {
const authUser = contextValue.authUser
if (!authUser) {
throw new GraphQLError('User is not authenticated', {
extensions: {
code: 'UNAUTHENTICATED',
http: { status: 401 },
},
})
}
try {
const post = await Post.findByIdAndUpdate(
args.postId,
args.updatePostInput,
{ new: true }
)
.populate('comments')
.populate('postedBy')
const updatedPost = {
id: post.id,
title: post.title,
postedBy: post.postedBy,
comments: post.comments,
}
// subscription postUpdated with object iterator POST_UPDATED
pubsub.publish('POST_UPDATED', { postUpdated: updatedPost })
return post
} catch (error) {
throw new GraphQLError(`Error: ${error.message}`, {
extensions: {
code: 'BAD_REQUEST',
http: { status: 400 },
argumentName: args,
},
})
}
},
},
// resolvers for post addition and post modification using subscribe function
Subscription: {
postAdded: {
subscribe: () => pubsub.asyncIterator('POST_ADDED'),
},
commentAdded: {
subscribe: () => pubsub.asyncIterator('COMMENT_ADDED'),
},
postUpdated: {
subscribe: () => pubsub.asyncIterator('POST_UPDATED'),
},
},
//Hard-coding the default resolvers is appropriate in some cases,
// but I think it is required in fields with references to other
//database models to avoid returning null field values.
Post: {
id: async (parent, args, contextValue, info) => {
return parent.id
},
title: async (parent) => {
return parent.title
},
postedBy: async (parent) => {
const user = await User.findById(parent.postedBy)
.populate('posts', { id: 1, title: 1, comments: 1, postedBy: 1 })
.populate('commentsMade')
//console.log('id', user.id)
//console.log('email', user.email)
return user
},
comments: async (parent) => {
return parent.comments
},
},
Comment: {
id: async (parent, args, contextValue, info) => {
return parent.id
},
text: async (parent, args, contextValue, info) => {
return parent.text
},
commenter: async (parent, args, contextValue, info) => {
const user = await User.findById(parent.commenter)
.populate('posts')
.populate('commentsMade')
return user
},
commentFor: async (parent, args, contextValue, info) => {
const post = await Post.findById(parent.commentFor)
.populate('comments')
.populate('postedBy')
return post
},
},
...
}
export default resolvers
主入口服务器文件(例如index.js)中的代码可能看起来像这样，例如
import dotenv from 'dotenv'
import { ApolloServer } from '@apollo/server'
import { expressMiddleware } from '@apollo/server/express4'
import { ApolloServerPluginDrainHttpServer } from '@apollo/server/plugin/drainHttpServer'
import { makeExecutableSchema } from '@graphql-tools/schema'
import { WebSocketServer } from 'ws'
import { useServer } from 'graphql-ws/lib/use/ws'
import express from 'express'
import http from 'http'
import cors from 'cors'
import bodyParser from 'body-parser'
import jwt from 'jsonwebtoken'
import UserModel from './models/User.js'
import typeDefs from './tpeDefs.js'
import resolvers from './resolvers.js'
import mongoose from 'mongoose'
dotenv.config()
mongoose.set('strictQuery', false)
let db_uri
if (process.env.NODE_ENV === 'development') {
db_uri = process.env.MONGO_DEV
}
mongoose.connect(db_uri).then(
() => {
console.log('Database connected')
},
(err) => {
console.log(err)
}
)
const startGraphQLServer = async () => {
const app = express()
const httpServer = http.createServer(app)
const schema = makeExecutableSchema({ typeDefs, resolvers })
const wsServer = new WebSocketServer({
server: httpServer,
path: '/',
})
const serverCleanup = useServer({ schema }, wsServer)
const server = new ApolloServer({
schema,
context: async ({ req }) => {
const authHeader = req.headers['authorization']
const token = authHeader && authHeader.split(' ')[1]
if (token) {
const decoded = jwt.verify(token, process.env.TOKEN_SECRET)
const authUser = await UserModel.findById(decoded.id)
.populate('commentsMade')
.populate('posts')
return { authUser }
}
},
plugins: [
ApolloServerPluginDrainHttpServer({ httpServer }),
{
async serverWillStart() {
return {
async drainServer() {
await serverCleanup.dispose()
},
}
},
},
],
})
await server.start()
app.use(
'/',
cors(),
bodyParser.json(),
expressMiddleware(server, {
context: async ({ req }) => {
const authHeader = req.headers['authorization']
const token = authHeader && authHeader.split(' ')[1]
if (token) {
const decoded = jwt.verify(token, process.env.TOKEN_SECRET)
const authUser = await UserModel.findById(decoded.id)
.populate('commentsMade')
.populate('posts')
return { authUser }
}
},
})
)
const PORT = 4000
httpServer.listen(PORT, () =>
console.log(`Server is now running on http://localhost:${PORT}`)
)
}
startGraphQLServer()
结束。是时候在阿波罗探索者沙盒中运行一些测试和检查了。认真定义所需的默认解析器，以避免Apollo服务器以您的名义发送空值。
要查看代码和实现，请转到此存储库。
编码快乐!