Access ordered LinkedHashMap not preserved following deserialisation.

[pferraro]

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• I had searched in the issues and found no similar issues.

Version

A serialised LinkedHashMap that was constructed to use access order (as opposed to insertion order), will lose this characteristic following deserialisation.

Component(s)

Java

Minimal reproduce step

Fory fory = Fory.builder().withLanguage(Language.JAVA).build();
LinkedHashMap<Integer, Integer> map = new LinkedHashMap<>(16, 0.75, true);
map.put(1, 1);
map.put(2, ");
map.put(3, 3);
map.put(4, 4);
LinkedHashMap<Integer, Integer> deserialised = (LinkedHashMap<Integer, Integer>) fory.deserialize(fory.serialize(map));

// This passes, as expected
assertEquals(map, deserialised);

// Modify access order
assertEquals(2, map.get(2));
assertEquals(4, map.get(4));
assertEquals(1, map.get(1));
assertEquals(3, map.get(3));

assertEquals(2, deserialised.get(2));
assertEquals(4, deserialised.get(4));
assertEquals(1, deserialised.get(1));
assertEquals(3, deserialised.get(3));

// This fails, since access order was not preserved
assertEquals(deserialised.values().iterator().next(), map.values().iterator().next());

What did you expect to see?

The last assertion should have succeeded (as it would when following Java serialization).

What did you see instead?

The last assertion fails.

Anything Else?

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!

[chaokunyang]

Thanks for reporting this issue, the fix is not complex, but it will break exising wire format.

Currently, you can register a serializer for LinkedHashMap by:

public static final class LinkedHashMapSerializer extends MapSerializer<LinkedHashMap> {
  private static final FieldAccessor ACCESS_ORDER_ACCESSOR =
      FieldAccessor.createAccessor(
          ReflectionUtils.getDeclaredField(LinkedHashMap.class, "accessOrder"));

  public LinkedHashMapSerializer(TypeResolver typeResolver) {
    super(typeResolver, LinkedHashMap.class, true);
  }

  @Override
  public Map onMapWrite(WriteContext writeContext, LinkedHashMap value) {
    Map map = super.onMapWrite(writeContext, value);
    if (!config.isXlang()) {
      writeContext.getBuffer().writeBoolean(ACCESS_ORDER_ACCESSOR.getBoolean(value));
    }
    return map;
  }

  @Override
  public LinkedHashMap newMap(
      ReadContext readContext, boolean entryReadAlwaysAdvances) {
    MemoryBuffer buffer = readContext.getBuffer();
    int numElements = readMapSize(readContext, buffer, entryReadAlwaysAdvances);
    setNumElements(numElements);

    boolean accessOrder = !config.isXlang() && buffer.readBoolean();
    LinkedHashMap hashMap = new LinkedHashMap(numElements, 0.75f, accessOrder);
    readContext.reference(hashMap);
    return hashMap;
  }

  @Override
  public Map newMap(Map map) {
    boolean accessOrder = ACCESS_ORDER_ACCESSOR.getBoolean(map);
    return new LinkedHashMap(map.size(), 0.75f, accessOrder);
  }
}

Then register it: fory.registerSerializer(LinkedHashMap.class, LinkedHashMapSerializer.class)

[chaokunyang]

We will update the wire format for this in fory 2.0