Reading file contents with casbah gridfs throws MalformedInputException - scala

Question

Consider the following sample code: it writes a file to mongodb and then tries to reread it
import com.mongodb.casbah.Imports._
import com.mongodb.casbah.gridfs.Imports._
object TestGridFS{
def main(args: Array[String]){
val mongoConn = MongoConnection()
val mongoDB = mongoConn("gridfs_test")
val gridfs = GridFS(mongoDB) // creates a GridFS handle on ``fs``
val xls = new java.io.FileInputStream("ok.xls")
val savedFile=gridfs.createFile(xls)
savedFile.filename="ok.xls"
savedFile.save
println("savedfile id: %s".format(savedFile._id.get))
val file=gridfs.findOne(savedFile._id.get)
val bytes=file.get.source.map(_.toByte).toArray
println(bytes)
}
}
this yields
gridfs $ sbt run
[info] Loading global plugins from /Users/jean/.sbt/plugins
[info] Set current project to gridfs-test (in build file:/Users/jean/dev/sdev/src/perso/gridfs/)
[info] Running TestGridFS
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
savedfile id: 504c8cce0364a7cd145d5dc1
[error] (run-main) java.nio.charset.MalformedInputException: Input length = 1
java.nio.charset.MalformedInputException: Input length = 1
at java.nio.charset.CoderResult.throwException(CoderResult.java:260)
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:319)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158)
at java.io.InputStreamReader.read(InputStreamReader.java:167)
at java.io.BufferedReader.fill(BufferedReader.java:136)
at java.io.BufferedReader.read(BufferedReader.java:157)
at scala.io.BufferedSource$$anonfun$iter$1$$anonfun$apply$mcI$sp$1.apply$mcI$sp(BufferedSource.scala:38)
at scala.io.Codec.wrap(Codec.scala:64)
at scala.io.BufferedSource$$anonfun$iter$1.apply(BufferedSource.scala:38)
at scala.io.BufferedSource$$anonfun$iter$1.apply(BufferedSource.scala:38)
at scala.collection.Iterator$$anon$14.next(Iterator.scala:148)
at scala.collection.Iterator$$anon$25.hasNext(Iterator.scala:463)
at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
at scala.io.Source.hasNext(Source.scala:238)
at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
at scala.collection.Iterator$class.foreach(Iterator.scala:660)
at scala.collection.Iterator$$anon$19.foreach(Iterator.scala:333)
at scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:48)
at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:99)
at scala.collection.TraversableOnce$class.toBuffer(TraversableOnce.scala:250)
at scala.collection.Iterator$$anon$19.toBuffer(Iterator.scala:333)
at scala.collection.TraversableOnce$class.toArray(TraversableOnce.scala:237)
at scala.collection.Iterator$$anon$19.toArray(Iterator.scala:333)
at TestGridFS$.main(test.scala:15)
at TestGridFS.main(test.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
java.lang.RuntimeException: Nonzero exit code: 1
at scala.sys.package$.error(package.scala:27)
[error] {file:/Users/jean/dev/sdev/src/perso/gridfs/}default-b6ab90/compile:run: Nonzero exit code: 1
[error] Total time: 1 s, completed 9 sept. 2012 14:34:22
I don't understand what the charset problem can be, I just wrote the file to the database. when querying the base I DO see the files and chunks in there, but can't seem to be able to read them.
I tried this with mongo 2.0 and 2.2, casbah 2.4 and 3.0.0-M2 to no avail, and don't see what I could do to get the bytes, on mac OSX mountain lion.
PS: To run the test, you can use the following build.sbt
name := "gridfs-test"
version := "1.0"
scalaVersion := "2.9.1"
libraryDependencies += "org.mongodb" %% "casbah" % "2.4.1"
libraryDependencies += "org.mongodb" %% "casbah-gridfs" % "2.4.1"
resolvers ++= Seq("Typesafe Releases" at "http://repo.typesafe.com/typesafe/releases/",
"sonatype release" at "https://oss.sonatype.org/content/repositories/releases",
"OSS Snapshots" at "https://oss.sonatype.org/content/repositories/snapshots/")
Here is the stacktrace I get :

Answer 1

I found a way to read the file contents back from mongodb. The source method relies on underlying.inpustream which is defined in GridFSDBFile.
Every test I did which uses underlying.inpustream failed with the same error.
However, the API proposes another way to access the files : writeTo. writeTo does not use underlying.inpustream.
Here is the "fixed" code from the question :
import com.mongodb.casbah.Imports._
import com.mongodb.casbah.gridfs.Imports._
object TestGridFS{
def main(args: Array[String]){
val mongoConn = MongoConnection()
val mongoDB = mongoConn("gridfs_test")
val gridfs = GridFS(mongoDB) // creates a GridFS handle on ``fs``
val xls = new java.io.File("ok.xls")
val savedFile=gridfs.createFile(xls)
savedFile.filename="ok.xls"
savedFile.save
println("savedfile id: %s".format(savedFile._id.get))
val file=gridfs.findOne(savedFile._id.get)
val byteArrayOutputStream = new java.io.ByteArrayOutputStream()
file.map(_.writeTo(byteArrayOutputStream))
byteArrayOutputStream.toByteArray
}
}
the last line, byteArrayOutputStream.toByteArray gives you an array of bytes which can then be used however you see fit.