如何使用 API 路由在 Next.js 上下载文件

Question

我正在使用 next.js。我有一个第三方服务，我需要从中检索 PDF 文件。该服务需要一个 API 密钥，我不想在客户端公开该密钥。

这是我的文件

/api/getPDFFile.js ...

  const options = {
    method: 'GET',
    encoding: 'binary',
    headers: {
      'Subscription-Key': process.env.GUIDE_STAR_CHARITY_CHECK_API_PDF_KEY,
      'Content-Type': 'application/json',
    },
    rejectUnauthorized: false,
  };

  const binaryStream = await fetch(
    'https://apidata.guidestar.org/charitycheckpdf/v1/pdf/26-4775012',
    options
  );
  
  return res.status(200).send({body: { data: binaryStream}});

pages/getPDF.js

   <button type="button" onClick={() => {
  fetch('http://localhost:3000/api/guidestar/charitycheckpdf',
    {
      method: 'GET',
      encoding: 'binary',
      responseType: 'blob',
    }).then(response => {
      if (response.status !== 200) {
        throw new Error('Sorry, I could not find that file.');
      }
      return response.blob();
    }).then(blob => {
      const url = window.URL.createObjectURL(blob);
      const a = document.createElement('a');
      a.style.display = 'none';
      a.href = url;
      a.setAttribute('download', 'test.pdf');
      document.body.appendChild(a);
      a.click();
      window.URL.revokeObjectURL(url);
    })}}>Click to Download</button>

点击按钮下载一个文件，但当我打开它时，我看到错误消息，“无法加载 PDF 文档。”

Answer 1

您似乎在使用 node-fetch。所以，你可以这样做：

// /pages/api/getAPI.js

import stream from 'stream';
import { promisify } from 'util';
import fetch from 'node-fetch';

const pipeline = promisify(stream.pipeline);
const url = 'https://w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf';

const handler = async (req, res) => {
  const response = await fetch(url); // replace this with your API call & options
  if (!response.ok) throw new Error(`unexpected response ${response.statusText}`);

  res.setHeader('Content-Type', 'application/pdf');
  res.setHeader('Content-Disposition', 'attachment; filename=dummy.pdf');
  await pipeline(response.body, res);
};

export default handler;

然后来自客户：

// /pages/index.js

const IndexPage = () => <a href="/api/getPDF">Download PDF</a>;
export default IndexPage;

CodeSandbox Link (open the deployed URL 在新标签页中查看它是否有效）

参考文献：

PS：我认为在这种情况下不需要太多的错误处理。如果您希望为您的用户提供更多信息，您可以。但是这么多代码也可以正常工作。如果出现错误，文件下载将失败并显示“服务器错误”。另外，我认为没有必要先创建 blob URL。您可以直接在您的应用程序中下载它，因为 API 同源。

早些时候 I had used request，也张贴在这里以备不时之需：

import request from 'request';
const url = 'https://w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf';
export default (_, res) => { request.get(url).pipe(res); };

Answer 2

@brc-dd 在这个问题上救了我。我必须添加的其中一件事是动态生成的 link 元素（请参阅代码中的 var link），一旦我们从 API 获得文件数据，它就会自行点击。这对于获得一致的下载非常重要（我之前没有得到）。

我创建 link 以下载文件的页面代码如下所示：

// the fileProps variable used below looks like {"file_name":"test.png", "file_type":"image/png", "file_size": 748833}
import Button from 'react-bootstrap/Button'
import { toast } from 'react-toastify';

const DataGridCell = ({ filename, filetype, filesize }) => {
    const [objFileState, setFileDownload] = useState({})

    // handle POST request here
    useEffect(() => {
        async function retrieveFileBlob() {
            try {
                const ftch = await fetch( // this will request the file information for the download (whether an image, PDF, etc.)
                    `/api/request-file`,
                    {
                        method: "POST",
                        headers: {
                            "Content-type": "application/json"
                        },
                        body: JSON.stringify(objFileState)
                    },
                )
                const fileBlob = await ftch.blob()

                // this works and prompts for download
                var link = document.createElement('a')  // once we have the file buffer BLOB from the post request we simply need to send a GET request to retrieve the file data
                link.href = window.URL.createObjectURL(fileBlob)
                link.download = objFileState.strFileName
                link.click()
                link.remove();  //afterwards we remove the element  
            } catch (e) {
                console.log({ "message": e, status: 400 })  // handle error
            }
        }

        if (objFileState !== {} && objFileState.strFileId) retrieveFileBlob()   // request the file from our file server

    }, [objFileState])

    // NOTE: it is important that the objFile is properly formatted otherwise the useEffect will just start firing off without warning
    const objFile = {
        "objFileProps": { "file_name": filename, "file_type": filetype, "file_size": filesize }
    }
    return <Button onClick={() => {toast("File download started"); setFileDownload(objFile) }} className="btn btn-primary m-2">Download {filename}</Button>

}

link 调用的我的本地 NextJs API 端点 (/api/qualtrics/retrieve-file) 看起来像：

/**
 * @abstract This API endpoint requests an uploaded file from a Qualtrics response
 * (see Qualtrics API reference for more info: 
https://api.qualtrics.com/guides/reference/singleResponses.json/paths/~1surveys~1%7BsurveyId%7D~1responses~1%7BresponseId%7D~1uploaded-files~1%7BfileId%7D/get)

 * For this API endpoint the parameters we will be:
 * Param 0 = Survey ID
 * Param 1 = Response ID
 * Param 2 = File ID
 * Param 3 = Header object (properties of the file needed to return the file to the client)
 *
 */
// This is a protected API route
import { getSession } from 'next-auth/client'

export default async function API(req, res) {
    // parse the API query
    const { params } = await req.query  // NOTE: we must await the assignment of params from the request query
    const session = await getSession({ req })
    const strSurveyId = await params[0]
    const strResponseId = await params[1]
    const strFileId = await params[2]
    const objFileProps = JSON.parse(decodeURIComponent(await params[3]))    // file properties
    // this if condition simply checks that a user is logged into the app in order to get data from this API
    if (session) {
        // ****** IMPORTANT: wrap your fetch to Qualtrics in a try statement to help prevent errors of headers already set **************
        try {
            const response = await fetch(
                `${process.env.QUALTRICS_SERVER_URL}/API/v3/surveys/${strSurveyId}/responses/${strResponseId}/uploaded-files/${strFileId}`,
                {
                    method: "get",
                    headers: {
                        "X-API-TOKEN": process.env.QUALTRICS_API_TOKEN
                    }
                }
            );

            // get the file information from the external API
            const resBlob = await response.blob();
            const resBufferArray = await resBlob.arrayBuffer();
            const resBuffer = Buffer.from(resBufferArray);
            if (!response.ok) throw new Error(`unexpected response ${response.statusText}`);

            // write the file to the response (should prompt user to download or open the file)
            res.setHeader('Content-Type', objFileProps.file_type);
            res.setHeader('Content-Length', objFileProps.file_size);
            res.setHeader('Content-Disposition', `attachment; filename=${objFileProps.file_name}`);
            res.write(resBuffer, 'binary');
            res.end();
        } catch (error) {
            return res.send({ error: `You made an invalid request to download a file ${error}`, status: 400 })
        }

    } else {
        return res.send({ error: 'You must sign in to view the protected content on this page...', status: 401 })
    }
}

如何使用 API 路由在 Next.js 上下载文件

How to download a file on Next.js using an API route

download

node.js

next.js