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Posted to commits@fory.apache.org by "pferraro (via GitHub)" <gi...@apache.org> on 2026/08/21 21:48:49 UTC

[I] Access ordered LinkedHashMap not preserved following deserialisation. [fory]

pferraro opened a new issue, #3965:
URL: https://github.com/apache/fory/issues/3965

   ### Search before asking
   
   - [x] I had searched in the [issues](https://github.com/apache/fory/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
   
   ```java
   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!


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Re: [I] Access ordered LinkedHashMap not preserved following deserialisation. [fory]

Posted by "mohithvardhan002 (via GitHub)" <gi...@apache.org>.
mohithvardhan002 commented on issue #3965:
URL: https://github.com/apache/fory/issues/3965#issuecomment-6021445916

   Hi @chaokunyang, I’d like to work on this issue and submit a PR for it.
   
   I understand that preserving `LinkedHashMap` access order requires updating the wire format for Fory 2.0, as discussed above. I’ll first inspect the existing `MapSerializer`/`LinkedHashMap` serialization path and add regression tests before implementing the fix.
   
   Please let me know if there are any additional considerations I should keep in mind.


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Re: [I] Access ordered LinkedHashMap not preserved following deserialisation. [fory]

Posted by "chaokunyang (via GitHub)" <gi...@apache.org>.
chaokunyang commented on issue #3965:
URL: https://github.com/apache/fory/issues/3965#issuecomment-5384202417

   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:
   
   ```java
   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);
     }
   }
   ```


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Re: [I] Access ordered LinkedHashMap not preserved following deserialisation. [fory]

Posted by "chaokunyang (via GitHub)" <gi...@apache.org>.
chaokunyang commented on issue #3965:
URL: https://github.com/apache/fory/issues/3965#issuecomment-5384208798

   We will update the wire format for this in fory 2.0


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