Nodejs保存JSON文件

Question

1. 说我有这个<input type="file" id="theFile">

2. 我使用 myVar = document.getElementById('theFile').value 访问所选文件

3. 输出为console.log(myVar); // C:\fakepath\xxx.txt

然后我做一个简单的 POST，做一个 POST 的方法有很多，但一个基本的 JavaScript 方法是：

var http = new XMLHttpRequest();
http.onreadystatechange = function() { 
http.open("POST", "http://localhost:port/upload-test");
http.setRequestHeader('Content-type', 'application/json');
var body = {
    file: document.getElementById('theFile').value
}
http.send(JSON.stringify(body));

然后在我的Nodejs Express 服务中我这样做：

app.post('/upload-test', (request, response) => {
    console.log(request.body); // { file: 'C:\\fakepath\\xxx.txt' }
});

现在如何将该文件保存到运行服务的电脑上？

我知道其他解决方案，例如https://www.w3schools.com/nodejs/nodejs_uploadfiles.asp，但这需要用户使用<form>，这不是我想要的。我想使用基本的 POST 和 JSON 方法上传文件。

Answer 1

请求的内容类型应该是multipart/form-data，因为您正在上传文件。 您可以使用 multerjs 进行 nodejs 上传

var express = require('express')
var multer  = require('multer')
var upload = multer({ dest: 'uploads/' })

var app = express()

app.post('/upload-test', upload.single('avatar'), function (req, res, next) {
  // req.file is the `avatar` file
  // req.body will hold the text fields, if there were any
})

Answer 2

客户端 首先，您需要将文件内容“读取”到变量中。您不能直接上传文件，如此处其他地方所述。

我不确定您使用的是什么客户端。例如。 React、Angular 或纯 Javascript。因此，这里有一个关于 SO 的另一篇文章的链接，该文章介绍了如何选择客户端文件并将其内容读入 var。 Read Client-Side file

在 var 中获得文件内容后，您可以“发布”它。例如

// Build the Headers object.
let headers = new Headers();
headers.append("Content-Type","application/json");

// Build the body object.
let body = {
    fileName: varContainingFileName,
    fileContent: varContianingContentsOfFile
};

// Build the request
const response = await fetch(URL, {method: 'POST',
                                    headers:headers, 
                                    body:JSON.stringify(body)});

// See what we get back from the service.  Note, for the await to work,
// Needs to be wrapped in async method.
console.log(response);

服务器端 我假设你已经为 API 设置了路由，所以直接进入......

const fs = require('fs');

uploadFile(req, res) {

    const requestBody = JSON.parse(req.body);

    log.info("Received File Upload request.  File " + requestBody.fileName);

    // If one doesn't exist, create a folder for the file
    fs.existsSync("./SomeFolder/") || fs.mkdirSync("./SomeFolder/");

    // Using method.then(otherMethod) with promises.
    writeSourceDataToFile (requestBody.fileName,
                            "./SomeFolder/",
                            requestBody.fileContent)
      .then(v => finalMethod(v, requestBody.fileName, "./SomeFolder/", res))
      .catch(err => returnError(res, err) );

}

function writeSourceDataToFile (fileName, path, content) {

    return new Promise((resolve, reject) => {

        // User fs write stream to stream the file content var to file.
        let writeSource = fs.createWriteStream(path + fileName)
            .on('end', function () {
                log.info("File wrote to disk - End event");
                resolve (true);
            })
           .on('finish', function () {
               log.info("File wrote to disk - Finish event");
               resolve (true);
            })
           .on('error', function (err) {
               log.info('Error whilst writing file - ' + fileName);
               reject (err);
           });

        writeSource.write(content);

        writeSource.end();

    });
}

function finalMethod(v, fileName, path, res) {

    // Final method just wraps things up and sends some message back to 
    // client.

    log.info(fileName + " File Upload Process Completed.");
    res.write("File Upload Process Completed.\n");

    res.status(200).end();

}

// Something went wrong, log it and tell the client.
function returnError(res, err) {
  log.error(err);
  res.status(500).send(err);
}

Answer 3

您可以使用 Multer 模块进行文件上传

const multer = require('multer');

现在设置destinatoin文件夹来保存上传的文件

const upload = multer({ dest: './uploads/' });

最后使用upload.single() 上传单个文件或使用upload.array() 上传多个文件

app.post('/upload-test',upload.single('myFile'),(request, response) => {
    console.log(request.body);
});