为什么当我使用 apollo-server 上传文件时，文件已上传但文件为 0kb？答案

【问题标题】：Why when I upload file with apollo-server the file is uploaded but the file is 0kb?为什么当我使用 apollo-server 上传文件时，文件已上传但文件为 0kb？
【发布时间】：2021-05-01 03:13:02
【问题描述】：

我试图解决这个问题，但我不明白为什么文件被上传但他的大小是 0Kb。我在教程中看到了这段代码，但他在那个教程上工作，但对我不起作用

const { ApolloServer, gql } = require('apollo-server');
const path = require('path');
const fs = require('fs');

const typeDefs = gql`
  type File {
    url: String!
  }

  type Query {
    hello: String!
  }

  type Mutation {
    fileUpload(file: Upload!): File!
  }
`;

const resolvers = {
  Query: {
    hello: () => 'Hello world!',
  },
  Mutation: {
    fileUpload: async (_, { file }) => {
      const { createReadStream, filename, mimetype, encoding } = await file;
      const stream = createReadStream();
      const pathName = path.join(__dirname, `/public/images/${filename}`);
      await stream.pipe(fs.createWriteStream(pathName));

      return {
        url: `http://localhost:4000/images/${filename}`,
      };
    },
  },
};

const server = new ApolloServer({
  typeDefs,
  resolvers,
});

server.listen().then(({ url }) => {
  console.log(`???? Server ready at ${url}`);
});

那么当我上传文件时，它是上传的，但是文件是0kb

like this

【问题讨论】：

标签： file-upload graphql apollo apollo-server apollostack

【解决方案1】：

发生的情况是解析器在文件上传之前返回，导致服务器在客户端完成上传之前做出响应。您需要在解析器中承诺并等待文件上传流事件。

这是一个例子：

https://github.com/jaydenseric/apollo-upload-examples/blob/c456f86b58ead10ea45137628f0a98951f63e239/api/server.js#L40-L41

在你的情况下：

const resolvers = {
  Query: {
    hello: () => "Hello world!",
  },
  Mutation: {
    fileUpload: async (_, { file }) => {
      const { createReadStream, filename } = await file;
      const stream = createReadStream();
      const path = path.join(__dirname, `/public/images/${filename}`);

      // Store the file in the filesystem.
      await new Promise((resolve, reject) => {
        // Create a stream to which the upload will be written.
        const writeStream = createWriteStream(path);

        // When the upload is fully written, resolve the promise.
        writeStream.on("finish", resolve);

        // If there's an error writing the file, remove the partially written
        // file and reject the promise.
        writeStream.on("error", (error) => {
          unlink(path, () => {
            reject(error);
          });
        });

        // In Node.js <= v13, errors are not automatically propagated between
        // piped streams. If there is an error receiving the upload, destroy the
        // write stream with the corresponding error.
        stream.on("error", (error) => writeStream.destroy(error));

        // Pipe the upload into the write stream.
        stream.pipe(writeStream);
      });

      return {
        url: `http://localhost:4000/images/${filename}`,
      };
    },
  },
};

请注意，使用这样的文件名来存储上传的文件可能不是一个好主意，因为以后使用相同文件名的上传会覆盖之前的文件。我不确定如果两个客户端同时上传两个同名文件会发生什么。

【讨论】：