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[Java教程]Node.js使用fs.renameSync报cross


  在Node.js中,我们可以使用formidable模块来轻松地实现文件上传功能,代码如下:

var Q = require('q');var util = require('util');var fs = require('fs');var path = require('path');var moment = require('moment');var formidable = require('formidable');var imageUpload = function (){};imageUpload.prototype.useFormParseCallback = function(req){  var deferred = Q.defer();  var form = new formidable.IncomingForm();  form.parse(req, deferred.makeNodeResolver());  return deferred.promise;};// 确保目录存在// 如果指定的目录不存在则同步创建(多层次)imageUpload.prototype.ensureUploadPathExist = function(uploadPath, mode){  if (!fs.existsSync(uploadPath)){    var pathtmp;    uploadPath.split(path.sep).forEach(function(dirname) {      if (pathtmp) {        pathtmp = path.join(pathtmp, dirname);      }      else {        pathtmp = dirname;      }      if (!fs.existsSync(pathtmp)) {        if (!fs.mkdirSync(pathtmp, mode)) {          return false;        }      }    });  }  return true;};imageUpload.prototype.uploadImage = function(req){  var pathName = '/uploadImgs/';  var uploadPath = path.join(__dirname, '../../public', pathName);  this.ensureUploadPathExist(uploadPath);  return this.useFormParseCallback(req).then(function(files){    var file = files[1].imagefile;    var fileType = file.type.split('/')[1];    var newFileName = 'upload_' + moment().format('x') + Math.random().toString().substr(2, 10) + '.' + fileType;    fs.renameSync(file.path, uploadPath + newFileName);    return pathName + newFileName;  });};module.exports = imageUpload;

  上述代码中使用了模块q来处理Node.js中的回调处理,有关如何使用q可以自己上百度搜索下,这里不再赘述。函数ensureUploadPathExist()可以确保上传文件的目标目录是存在的,如果不存在它会逐级创建。文件被上传在/public/uploadImgs/目录下,并且按照指定的格式进行了重命名以防止文件被覆盖,有问题的地方在fs.renameSync()函数的调用。正常情况下如果上传的目录在本地,执行fs.renameSync()函数重命名文件是不会有问题的,但如果是跨分区重命名,例如在Linux中使用了NFS或者共享目录,则此处会报跨分区重命名的权限错误。解决办法是将fs.renameSync()函数替换为下面的代码:

var readStream = fs.createReadStream(file.path);var writeStream = fs.createWriteStream(uploadPath + newFileName); var deferred = Q.defer();util.pump(readStream, writeStream, deferred.makeNodeResolver());return deferred.promise.then(function() {  fs.unlinkSync(file.path);  return pathName + newFileName;});

  使用上述代码既可以实现本地文件的上传,也可以实现跨分区的文件上传。