On Wed, Apr 17, 2019 at 6:34 PM Artashes Aghajanyan <[email protected]> wrote: > > I noticed the following behavior that feels like a bug to me, but I want to > confirm if it's not by design before opening an issue in github. > > jackson-databind-2.4.3 > > Consider the following code fragment: > > ByteBuf in = ... // a bytebuf containing multiple jsons, e.g. > {"ack":"a1"}{"ack":"b1"}{"ack":"b3"} > ByteBufInputStream inputStream = new ByteBufInputStream(in); > Map<String, String> ackMap = mapper.readValue(inputStream, Map.class); > > After this readValue() call, inputStream becomes empty (nothing left to read) > but only the first {"ack":"a1"} object is parsed and returned. I debugged it > a bit, here's what's happening: > > ObjectMapper.readValue(InputStream src, Class<T> valueType) calls > _jsonFactory.createParser(src) which calls > ByteSourceJsonBootstrapper.detectEncoding() which calls > ByteSourceJsonBootstrapper.ensureLoaded(4). > > ensureLoaded(4) basically tries to read 4k bytes from the stream. > > If the input stream contains multiple small (less than 4k?) json objects, it > reads everything from the stream, just to detect the encoding! > > The problem with this approach is that once the data is read from the stream > it is essentially lost for the user of object mapper, so if we have a stream > that contains a series of small json strings, it'll read all of it just to > detect the encoding but will only return the first json from readValue() call. > > Since ObjectMapper doesn't "own" the stream, one may expect that it won't > consume more data from the stream than is necessary to parse one json object. > > I've also tried this with the latest 2.9.8 release and the behavior is the > same. > > Is this a bug?
No, it is by design. Decoding is most efficient directly accessing byte[] for content, and overhead for reads from InputStream is non-trivial (depending on type of stream). Reads request buffer full of content, although if stream returns less whatever is available is consumed first before requesting more. If content buffered needs to be recovered for some reason it is available using one of 2 methods: releaseBuffered(OutputStream) releaseBuffered(Writer) which will then pass buffered but unused content, if any; method to call depends on kind of input source parser has been created with. -+ Tatu +- -- You received this message because you are subscribed to the Google Groups "jackson-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. For more options, visit https://groups.google.com/d/optout.
