Storing a Leap Frame

We are able to save and load a leap frame using several different serialization strategies. The provided formats are:

  1. JSON
  2. Avro
  3. Binary

It is also possible to create your own serialization formats if these do not suit your usage needs.

Sample Leap Frame

All serialization examples will use this leap frame.

val schema = StructType(StructField("features", TensorType(BasicType.Double)),
  StructField("name", ScalarType.String),
  StructField("list_data", ListType(BasicType.String)),
  StructField("nullable_double", ScalarType(BasicType.Double, true)),
  StructField("float", ScalarType.Float),
  StructField("byte_tensor", TensorType(BasicType.Byte)),
  StructField("short_list", ListType(BasicType.Short)),
  StructField("nullable_string", ScalarType(BasicType.String, true))).get
val dataset = Seq(Row(Tensor.denseVector(Array(20.0, 10.0, 5.0)),
  "hello", Seq("hello", "there"),
  Option(56.7d), 32.4f,
  Tensor.denseVector(Array[Byte](1, 2, 3, 4)),
  Seq[Short](99, 12, 45),
val frame = DefaultLeapFrame(schema, dataset)


// Store Leap Frame
for(bytes <- frame.writer("ml.combust.mleap.json").toBytes();
    frame2 <- FrameReader("ml.combust.mleap.json").fromBytes(bytes)) {
  println(new String(bytes)) // print the JSON bytes
  assert(frame == frame2)


// Store Leap Frame
for(bytes <- frame.writer("ml.combust.mleap.avro").toBytes();
    frame2 <- FrameReader("ml.combust.mleap.avro").fromBytes(bytes)) {
  println(new String(bytes)) // print the Avro bytes
  assert(frame == frame2)


Most efficient storage, uses data input/output streams to serialize the leap frame data.

// Store Leap Frame
for(bytes <- frame.writer("ml.combust.mleap.binary").toBytes();
    frame2 <- FrameReader("ml.combust.mleap.binary").fromBytes(bytes)) {
  println(new String(bytes)) // print the binary bytes
  assert(frame == frame2)


It is possible to create custom serializers for leap frames.

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