如何使用Node.js 0.10中的读取流立即链接写入流?

时间:2013-06-13 22:40:02

标签: node.js stream mongoose pipe gridfs

以下行将从指定的url变量下载图像文件:

var filename = path.join(__dirname, url.replace(/^.*[\\\/]/, ''));
request(url).pipe(fs.createWriteStream(filename));

这些行将获取该图像并保存到MongoDB GridFS:

 var gfs = Grid(mongoose.connection.db, mongoose.mongo);
 var writestream = gfs.createWriteStream({ filename: filename });
 fs.createReadStream(filename).pipe(writestream);

像这样链接pipe会抛出 错误:500无法管道。不可管理。

request(url).pipe(fs.createWriteStream(filename)).pipe(writestream);

这是因为图像文件尚未准备好读取,对吧?我该怎么做才能解决这个问题?错误:500无法管道。不可管理。

使用以下内容: Node.js 0.10.10 mongoose 请求 gridfs-stream

3 个答案:

答案 0 :(得分:11)

request(url).pipe(fs.createWriteStream(filename)).pipe(writestream);

与此相同:

var fileStream = fs.createWriteStream(filename);
request(url).pipe(fileStream);
fileStream.pipe(writestream);

所以问题在于您尝试将.pipe一个WriteStream转换为另一个WriteStream

答案 1 :(得分:8)

// create 'fs' module variable
var fs = require("fs");

// open the streams
var readerStream = fs.createReadStream('inputfile.txt');
var writerStream = fs.createWriteStream('outputfile.txt');

// pipe the read and write operations
// read input file and write data to output file
readerStream.pipe(writerStream);

答案 2 :(得分:3)

我认为链接管道的混乱是由于管道方法隐含地“自行选择”返回管道而引起的。那就是:

readableStream.pipe(writableStream) // Returns writable stream
readableStream.pipe(duplexStream) // Returns readable stream

但是一般规则说“你只能将可写流传输到可读流”。换句话说,只有可读流具有pipe()方法。