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Can anyone recommend a JSON library for Java which allows me to give it chunks of data as they come in, in a non-blocking fashion? I have read through A better Java JSON library and similar questions, and haven't found precisely what I'd like.

Essentially, what I'd like is a library which allows me to do something like the following:

String jsonString1 = "{ \"A broken";
String jsonString2 = " json object\" : true }";

JSONParser p = new JSONParser(...);
p.parse(jsonString1);
p.isComplete(); // returns false
p.parse(jsonString2);
p.isComplete(); // returns true
Object o = p.getResult();

Notice the actual key name ("A broken json object") is split between pieces.

The closest I've found is this async-json-library which does almost exactly what I'd like, except it cannot recover objects where actual strings or other data values are split between pieces.

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Tim C
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3 Answers3

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There are a few blocking streaming/incemental JSON parsers (as per Is there a streaming API for JSON?); but for async nothing yet that I am aware of. The lib you refer to seems badly named; it does not seem to do real asynchronous processing, but merely allow one to parse sequence of JSON documents (which multiple other libs allow doing as well)

If there were people who really wanted this, writing one is not impossible -- for XML there is Aalto, and handling JSON is quite a bit simpler than XML. For what it is worth, there is actually this feature request to add non-blocking parsing mode for Jackson; but very few users have expressed interest in getting that done (via voting for the feature request).

EDIT: (2016-01) while not async, Jackson ObjectMapper allows for convenient sub-tree by sub-tree binding of parts of the stream as well -- see ObjectReader.readValues() (ObjectReader created from ObjectMapper), or short-cut versions of ObjectMapper.readValues(...). Note the trailing s in there, which implies a stream of Objects, not just a single one.

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StaxMan
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0

Google Gson can incrementally parse Json from an InputStream https://sites.google.com/site/gson/streaming

Andrejs
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I wrote such a parser: JsonParser.java. See examples how to use it:JsonParserTest.java.

Alexei Kaigorodov
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