Throwing NoContentException when InputStream is empty

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."

Signed-off-by: Markus KARG <markus@headcrashing.eu>

media/json-binding/src/main/java/org/glassfish/jersey/jsonb/internal/JsonBindingProvider.java

@@ -19,6 +19,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.io.PushbackInputStream;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Type;
 
@@ -29,6 +30,7 @@
 import javax.ws.rs.core.Context;
 import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.MultivaluedMap;
+import javax.ws.rs.core.NoContentException;
 import javax.ws.rs.ext.ContextResolver;
 import javax.ws.rs.ext.Provider;
 import javax.ws.rs.ext.Providers;
@@ -70,7 +72,24 @@ public Object readFrom(Class<Object> type, Type genericType,
                            MediaType mediaType,
                            MultivaluedMap<String, String> httpHeaders,
                            InputStream entityStream) throws IOException, WebApplicationException {
+        if (entityStream.markSupported()) {
+            entityStream.mark(1);
+            if (entityStream.read() == -1) {
+                throw new NoContentException("JSON-B cannot process empty input stream");
+            }
+            entityStream.reset();
+        } else {
+            final PushbackInputStream buffer = new PushbackInputStream(entityStream);
+            final int firstByte = buffer.read();
+            if (firstByte == -1) {
+                throw new NoContentException("JSON-B cannot process empty input stream");
+            }
+            buffer.unread(firstByte);
+            entityStream = buffer;
+        }
+
         Jsonb jsonb = getJsonb(type);
+
         try {
             return jsonb.fromJson(entityStream, genericType);
         } catch (JsonbException e) {