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From "Mann Du (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-1636) C++ JsonDecoder expects json object to be ordered
Date Thu, 29 Jan 2015 17:40:35 GMT

    [ https://issues.apache.org/jira/browse/AVRO-1636?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14297206#comment-14297206
] 

Mann Du commented on AVRO-1636:
-------------------------------

Did I mention that I confirmed the same behavior in Avro c++ 1.7.7? Thanks.  -Mann

> C++ JsonDecoder expects json object to be ordered
> -------------------------------------------------
>
>                 Key: AVRO-1636
>                 URL: https://issues.apache.org/jira/browse/AVRO-1636
>             Project: Avro
>          Issue Type: Bug
>          Components: c++
>    Affects Versions: 1.7.7
>            Reporter: Mann Du
>
> I am using  Shafquat Rahman's original post for this problem reported in Avro user mailing
list in last May for the description - ( Thiru provided a fix for the exact problem for Java
in Oct. 2011 with Avro-895.)
> I have been experimenting with avro in C++ (version 1.7.5) and ran into an issue with
the json decoder which expects ordered json objects. The problem I am seeing appears similar
to this post I found for an older avro java library:
> http://search-hadoop.com/m/7WG37aVaBd/v=plain
> I have a simple record:
> {
>     "name" : "SimpleRecord",
>     "type" : "record",
>     "fields" :[ 
>         { "name" : "A", "type" : "int"},
>         { "name" : "B", "type" : "int"}
>     ]
> }
> I generate the C++ header using avrogencpp. The generated  code has codec_traits specialization
for SimpleRecord that fixes the order for the JsonEncoder and JsonDecoder.
> ...snip...
> namespace avro {
> template<> struct codec_traits<SimpleRecord> {
>     static void encode(Encoder& e, const SimpleRecord& v) {
>         avro::encode(e, v.A);
>         avro::encode(e, v.B);
>     }
>     static void decode(Decoder& d, SimpleRecord& v) {
>         avro::decode(d, v.A);
>         avro::decode(d, v.B);
>     }
> };
> ...snip...
> The JsonDecoder successfully decodes json objects of the form{"A" : 1, "B" : 2} into
SimpleRecord. But if I try to decode {"B" : 2, "A" : 1} it throws 'avro::Exception' with "Incorrect
field" from impl/parsing/JsonCodec.cc:182 in the following method:
> JsonDecoderHandler(JsonParser& p) : in_(p) { }
>     size_t handle(const Symbol& s) {
>         switch (s.kind()) {
>         case Symbol::sRecordStart:
>             expectToken(in_, JsonParser::tkObjectStart);
>             break;
>         case Symbol::sRecordEnd:
>             expectToken(in_, JsonParser::tkObjectEnd);
>             break;
>         case Symbol::sField:
>             expectToken(in_, JsonParser::tkString);
>             if (s.extra<string>() != in_.stringValue()) {
>                 throw Exception("Incorrect field");
>             }
>             break;
>         default:
>             break;
>         }
>         return 0;
>     }
> The stack shows that avro::decode(d, v.A) is  the call the eventually causes the exception.
> According to the json spec the fields in a json object are unordered. ...



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