问题
I am sending an image in base64 format in a json message
image:["data:image/png;base64,iVBORw...","data:image/png;base64,idfsd..."]
I want to store this image in Cassandra. This json maps to my model as an Array[String] -
case class ImageArray(
image: Array[String]
}
I have read that to store images in cassandra, I need ByteBuffer. So I use ByteBuffer.wrap() to convert the array different indexes of the array into ByteBuffer.
ByteBuffer.wrap(model.image(0).getBytes()) //for the moment, I am taking only 1 image
I am unable to figure out how to conovert the ByteBuffer back into a String. I can retrieve the bytes from Cassandra like follows
(row.getBytes("image"))
The above gives me a ByteBuffer. How do I convert this into a String which I could use later to create an Array[String]
回答1:
Though I was able to solve it, the method was very slow so I dropped the idea of storing images as bytes and kept them as string (base64) as that is what I am getting from the server.
Coming to the original issue, to solve the problem, I made a few changes.
Changed Array to List in the model as Cassandra understand Lists
case class ImageArray(
image: List[String]
}
The json array or images mapped to image list by creating a custom Reads - (JsPath \ "image").read[List[String]]
In cassandra, the table schema for storing the image arrays was image list<blob>,
Once I had the List in the model, I converted it into List of String into List of Byte using .value("image",seqAsJavaList(((ByteBuffer.wrap(model.image(0).getBytes())).array().toList):::((ByteBuffer.wrap(model.image(1).getBytes())).array().toList)))
Above, I took the first element of image list (a string which is base64 representation of image at index 0), convert it into byte using ByteBuffer.wrap, then converted ByteBuffer to Array and then converted it to List. This gave me List[Byte] for 1st image. I repeat it for image(1) and then join the two images using :::. Then I convert this Scala List to Java using seqAsJavaList.
Note: As the above method required multiple conversions, it isn't a optimal way. I instead decided to store the image as List[String]
来源：https://stackoverflow.com/questions/51844961/how-to-store-and-retrieve-base64-encoded-image-in-cassandra