Jackson: Deserialize map with non String keys #244

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1. xerial

   added this to the v07 milestone on Jun 23, 2015
2. komamitsu

   closed this as completedin #271on Aug 9, 2015
3. komamitsu commented on Aug 9, 2015

   

   komamitsu

   on Aug 9, 2015

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   @fdinoff In #271, jackson-dataformat-msgpack supports Boolean, Integer and Float type key while byte array key seemed to work before the change.

   BTW, you tried to use Map<byte[], Integer> map but I don't think it's easy to use byte[] as a key of Map since byte[]#equals doesn't match other byte arrays which have the same values.

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4. simpleseeker commented on Aug 10, 2015

   

   simpleseeker

   on Aug 10, 2015

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   On Sunday, August 9, 2015, Mitsunori Komatsu notifications@github.com
   wrote:

   @fdinoff https://github.com/fdinoff In #271
   #271,
   jackson-dataformat-msgpack supports Boolean, Integer and Float type key
   while byte array key seemed to work before the change.

   BTW, you tried to use Map<byte[], Integer> map but I don't think it's
   easy to use byte[] as a key of Map since byte[]#equals doesn't match
   other byte arrays which have the same values.

   —
   Reply to this email directly or view it on GitHub
   #244 (comment)
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5. fdinoff commented on Aug 20, 2015

   

   fdinoff

   on Aug 20, 2015

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   @komamitsu Thanks for adding this.

   Would it be possible to get a Map<String, Integer> map back if byte[] was the key of the map? The user would have to provide the enocding (By passing a Charset) so that you could decode it properly.
6. komamitsu commented on Aug 21, 2015

   

   komamitsu

   on Aug 21, 2015

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   Map<String, Integer> can be obtained from Map<byte[], Integer> easily like this and I don't think this library doesn't need to provide it.

           Map<byte[], Integer> orig = new HashMap<>();
           orig.put("aa".getBytes(), 1111);
           orig.put("bb".getBytes(), 2222);
   
           Map<String, Integer> converted = orig.entrySet().stream().collect(
                   Collectors.toMap(e -> new String(e.getKey()), Map.Entry::getValue));
   
7. fdinoff commented on Aug 23, 2015

   

   fdinoff

   on Aug 23, 2015

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   @komamitsu Sorry, didn't realize that byte[] was a valid key now.

   The problem now is what happens if the bytes weren't valid utf8? is the conversion to String and back to a byte array lossless? The doc for String#getBytes() says its unspecified, so the conversion isn't lossless. Losing valid data would be undesirable.

   Also I don't think you can deserialize into an actual object. (Is there?)

   Example: You have the following class

   class SomeObject {
       public Integer hello;
   }

   I would expect something like the following to work (the byte array is utf16 encoded.

   ByteArrayOutputStream out = new ByteArrayOutputStream();
   MessagePacker messagePacker = MessagePack.newDefaultPacker(out).packMapHeader(1);
   byte[] bytes = "Hello".getBytes(StandardCharsets.UTF_16); 
   messagePacker.packBinaryHeader(bytes.length).writePayload(bytes);
   messagePacker.packInt(42);
   messagePacker.close();
   
   SomeObject o = objectMapper.readValue(out.toByteArray(), SomeObject.class);
   assertEquals(42, o.hello);