使用Anorm（Scala / PlayFramework 2）在Postgres中保存/加载图像

Question

I think I'm saving the image to Postgres correctly, but get unexpected results trying to load the image. I don't really know if the error is in save or load.

Here is my Anorm code for saving the image:

def storeBadgeImage(badgeHandle: String, imgFile: File) = {
   val cmd = """
        |update badge
        |set img={imgBytes}
        |where handle = {badgeHandle}
  """
  var fis = new FileInputStream(imgFile)
  var imgBytes: Array[Byte] = Resource.fromInputStream(fis).byteArray
  // at this point I see the image in my browser if I return the imgBytes in the HTTP response, so I'm good so far.
  DB.withConnection { implicit c =>
  {
    try {
      SQL(cmd stripMargin).on("badgeHandle" -> badgeHandle, "imgBytes" -> imgBytes).executeUpdate() match {
        case 0 => "update failed for badge " + badgeHandle + ", image " + imgFile.getCanonicalPath
        case _ => "Update Successful"
      }
    } catch {
      case e: SQLException => e.toString()
    }
  }
}

}

...I get "update succesful", so I presume the save is working (I could be wrong). Here is my code for loading the image:

def fetchBadgeImage(badgeHandle: String) = {
    val cmd = """
        |select img from badge
        |where handle = {badgeHandle}
  """
  DB.withConnection { implicit c =>
    SQL(cmd stripMargin).on("badgeHandle" -> badgeHandle)().map {
      case Row(image: Array[Byte]) => {
        "image = " + image
      }
      case Row(Some(unknown: Any)) => {
        println(unknown + " unknown type is " + unknown.getClass.getName)  //[B@11be1c6 unknown type is [B
        "unknown"
      }
  }
}

}

...rather than going into the case "Row(image: Array[Byte])" as hoped, it goes into the "Row(Some(unknown: Any))" case. My println outputs "[B@11be1c6 unknown type is [B"

I don't know what type [B is or where I may have gone wrong...

Answer 1

It's an array of byte in Java(byte[]). > "I don't know what type [B".

And You can write match { case Row(Some(image: Array[Byte])) => } too in this case and that might be better.

Or you might be able to do that as follows.

val results: Stream[Array[Byte]] = SQL(cmd stripMargin)
  .on("badgeHandle" -> "name")().map { row => row[Array[Byte]]("img") }

...Oops, got the following compile error.

<console>:43: error: could not find implicit value for parameter c: anorm.Column[Array[Byte]]
          val res: Stream[Array[Byte]] = SQL(cmd stripMargin).on("badgeHandle" -> "name")().map { row => row[Array[Byte]]("img") }

Unfortunately, scala.Array is not supported by default. If you imitate the way of other types, It works.

implicit def rowToByteArray: Column[Array[Byte]] = {
  Column.nonNull[Array[Byte]] { (value, meta) =>
    val MetaDataItem(qualified, nullable, clazz) = meta
    value match {
      case bytes: Array[Byte] => Right(bytes)
      case _ => Left(TypeDoesNotMatch("..."))
    }
  }
}
val results: Stream[Array[Byte]] = SQL(cmd stripMargin)
  .on("badgeHandle" -> "name")().map { row => row[Array[Byte]]("img") }

https://github.com/playframework/Play20/blob/master/framework/src/anorm/src/main/scala/anorm/Anorm.scala