使用node.js,mongoose,gridfs-stream读取文件 [英] Read file with node.js, mongoose, gridfs-stream
问题描述
我正在使用mongoose和gridfs-stream来存储和读取mongodb中的文件.我在这里遵循以下示例: https://github.com/aheckmann/gridfs-stream
I am using mongoose and gridfs-stream to store and read files from mongodb. I am following the example here: https://github.com/aheckmann/gridfs-stream
将文件写入db可以正常工作,但是读取文件时遇到了问题.
Writing files into db is working fine but I faced a problem to read files.
mongodb的外观(显示集合)
What the mongodb looks (show collections)
fs.chunks
fs.files
文件索引的外观(db.fs.files.find())
What the file index looks (db.fs.files.find())
{ "_id" : ObjectId("5140392659851df70b000001"),
"filename" : "cover",
"contentType" : "binary/octet-stream",
"length" : 85734,
"chunkSize" : 262144,
"uploadDate" : ISODate("2013-03-13T08:30:30.299Z"),
"aliases" : null,
"metadata" : null,
"md5" : "4476b26067daa0677978ba501308a35d" }
然后我使用此代码来获取名为"cover"的文件
Then I use this code to get file named "cover"
...
var gfs = Grid(mongoose.connection.db, mongoose.mongo)
var readstream = gfs.createReadStream('cover')
发生错误:
Error: cover does not exist
at self.collection.self.fileId (/mypath/node_modules/mongoose/node_modules/mongodb/lib/mongodb/gridfs/gridstore.js:198:26)
at Cursor.nextObject (/mypath/node_modules/mongoose/node_modules/mongodb/lib/mongodb/cursor.js:654:35)
at Cursor.close (/mypath/node_modules/mongoose/node_modules/mongodb/lib/mongodb/cursor.js:960:5)
at Cursor.nextObject (/mypath/node_modules/mongoose/node_modules/mongodb/lib/mongodb/cursor.js:654:17)
at Cursor.nextObject.commandHandler (/mypath/node_modules/mongoose/node_modules/mongodb/lib/mongodb/cursor.js:631:14)
at Db._executeQueryCommand (/mypath/node_modules/mongoose/node_modules/mongodb/lib/mongodb/db.js:1702:5)
at g (events.js:185:14)
at EventEmitter.emit (events.js:115:20)
at Server.Base._callHandler (/mypath/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/base.js:130:25)
at Server.connect.connectionPool.on.server._serverState (/mypath/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/server.js:517:20)
我搜索了它,发现了一些可能的相关链接:
I googled it and found some possible related links:
https://github.com/mongodb/node-mongodb-native /issues/621
为什么gridfs get不能仅通过文件名来处理文件ID(ObjectId)
推荐答案
GitHub上的示例代码有点误导;我最初收到与您相同的错误消息.就我而言,这是由于我试图在写入流完成之前读取文件.我通过在事件处理程序中进行"close"
的读取来解决了此问题:
The example code on GitHub was a little bit misleading; I initially received the same error message you did. In my case, it was due to the fact that I was attempting to read the file before the write stream had finished. I resolved this by doing the read inside the event handler for "close"
:
var fs = require("fs"),
mongo = require("mongodb"),
Grid = require("gridfs-stream"),
gridfs,
writeStream,
readStream,
buffer = "";
mongo.MongoClient.connect("mongodb://localhost/gridfs_test", function (err, db) {
"use strict";
gridfs = Grid(db, mongo);
// write file
writeStream = gridfs.createWriteStream({ filename: "test.txt" });
fs.createReadStream("test.txt").pipe(writeStream);
// after the write is finished
writeStream.on("close", function () {
// read file, buffering data as we go
readStream = gridfs.createReadStream({ filename: "test.txt" });
readStream.on("data", function (chunk) {
buffer += chunk;
});
// dump contents to console when complete
readStream.on("end", function () {
console.log("contents of file:\n\n", buffer);
});
});
});
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