Disqus question: (de-)serialize properties of type List, Set or Long[]?

[simerplaha]

Question posted on Disqus - Link

Quoting: "Any ideas how to (de-)serialize properties of type List, Set or Long[]?"

[simerplaha]

I'm assuming you are using Java since you mentioned Long[]. In general you should be able to serialise and de-serialise however you like.

I think we need to support some external serialisation library for Java so getting started is easier.

But here's an example using raw bytes.

You will see an output like the following:

Key: 1
Value: [1, 2, 3, 4]
Key: 2
Value: [5, 6, 7, 8]
Key: 3
Value: [9, 10, 11, 12]

Example

import swaydb.data.slice.Slice;
import swaydb.data.slice.SliceReader;
import swaydb.data.util.ByteOps;
import swaydb.java.Map;
import swaydb.java.memory.MemoryMap;
import swaydb.java.serializers.Serializer;

import java.util.Arrays;

import static swaydb.java.serializers.Default.intSerializer;

class SerialisingArrayExample {

  public static void main(String[] args) {
    Serializer<long[]> longArraySerializer = new Serializer<long[]>() {
      @Override
      public Slice<Byte> write(long[] data) {
        int requiredHeaderBytes = Integer.BYTES; //for storing the length of array
        int requiredDataBytes = data.length * Long.BYTES; //for storing actual data
        int totalBytesRequired = requiredHeaderBytes + requiredDataBytes; //total count
        Slice<Byte> slice = Slice.ofBytesJava(totalBytesRequired); //create a slice instance
        slice.addInt(data.length, ByteOps.Java()); //write the number of longs in the array
        for (Long longVal : data) { //write the long[] values
          slice.addLong(longVal, ByteOps.Java());
        }
        return slice; //return the slice
      }

      @Override
      public long[] read(Slice<Byte> slice) {
        SliceReader<Byte> reader = slice.createReader(ByteOps.Java()); //create reader from the slice
        int longCount = reader.readInt(); //read header: number of longs
        long[] longs = new long[longCount]; //create the long array to add to
        for (int i = 0; i < longCount; i++) {
          longs[i] = reader.readLong(); //read the long values and set it in the array
        }
        return longs; //return the long
      }
    };

    Map<Integer, long[], Void> map = MemoryMap.functionsOff(intSerializer(), longArraySerializer).get();

    //add some data
    map.put(1, new long[]{1L, 2L, 3L, 4L});
    map.put(2, new long[]{5L, 6L, 7L, 8L});
    map.put(3, new long[]{9L, 10L, 11L, 12L});

    //print out the key-values
    map.forEach(keyValue -> {
      System.out.println("Key: " + keyValue.key());
      System.out.println("Value: " + Arrays.toString(keyValue.value()));
    });
  }
}

[BePe2]

tnx a lot for the example (and yeah, I meant java). Very nice. Could you give another example where the long[] is a property of a class which also has int or String properties? I can't figure out the serializer.write-Method-Signature (especially the Generic of Slice.

I'd vote for 3rd party serializer libs(like kryo or similar). Why reinvent the wheel? ;-)

regards

[simerplaha]

Totally. Should support Kryo for sure.

I think what you are looking for in the master branch. There are heaps fo test-cases that create serialisers. Take a look at this which is similar to what you are asking for.