Throwing NoContentException when InputStream is empty

[mkarg]

Since JAX-RS 2.1 an MBR must react upon an empty stream either with an empty instance or with NoContentException, but Jersey's JSON-B MBR does neither - it simply throws ProcessingException:

"In case the entity input stream is empty, the reader is expected to either return a Java representation of a zero-length entity or throw a javax.ws.rs.core.NoContentException in case no zero-length entity representation is defined for the supported Java type."

[mkarg]

This PR proposes a solution which reconstitutes compliance with JAX-RS 2.1 with a two-step approach to detect an empty input stream:

• First it tries to use mark/reset as this is very fast, but not guaranteed to be supported by all kinds of input streams.
• If this is not possible, then it will actively buffer the first byte, which is rather slow, but will work with all kinds of input stream.

As long as we allow this MBR to be used with other JAX-RS implementations (not just Jersey), we need this PR, and we need this two-step approach. An alternative solution could be to clearly restrict this MBR to work on Jersey only (e. g. by documentation or even technical checks), in which case we could leave out one of the two steps as we then know for sure the type of input stream Jersey will run this MBR with.

[mkarg]

Please see also jakartaee/rest#795.

[mkarg]

@spericas @chkal I assume this is the code location where you want the topic discussed in jakartaee/rest#795 to be handled (rather than the JAX-RS spec). :-)

[jansupol]

Is it possible to add a test checking the behaviour for an empty stream?

[mkarg]

Is it possible to add a test checking the behaviour for an empty stream?

Added unit test covering this issue with 4c6b2ac.

[senivam]

just another thought... previous comment was wrong :)
modify main method this way:

@Override
    public Object readFrom(Class<Object> type, Type genericType,
                           Annotation[] annotations,
                           MediaType mediaType,
                           MultivaluedMap<String, String> httpHeaders,
                           InputStream entityStream) throws IOException, WebApplicationException {

        final EntityInputStream streamWithMark =  new EntityInputStream(entityStream);
        entityStream = streamWithMark;
        if (streamWithMark.isEmpty()) {
            throw new NoContentException(LocalizationMessages.ERROR_JSONB_EMPTYSTREAM());
        }

        Jsonb jsonb = getJsonb(type);

        try {
            return jsonb.fromJson(entityStream, genericType);
        } catch (JsonbException e) {
            throw new ProcessingException(LocalizationMessages.ERROR_JSONB_DESERIALIZATION(), e);
        }
    }

[mkarg]

just another thought... previous comment was wrong :)

Cool optimization! 😎 If you are sure it is as safe and as fast I would be happy to accept your PR ontop! 👍

[senivam]

@mkarg, OK, I've submitted a PR to your branch :)