Calling jcrSession.getValueFactory().createBinary(is)) to upload a text file causes:

java.nio.channels.ClosedChannelException
at sun.nio.ch.FileChannelImpl.ensureOpen(FileChannelImpl.java:88)
at sun.nio.ch.FileChannelImpl.size(FileChannelImpl.java:289)
at org.modeshape.graph.property.basic.FileInputStreamBinary.getSize(FileInputStreamBinary.java:81)
at org.modeshape.connector.store.jpa.util.Serializer.serializeProperty(Serializer.java:315)
at org.modeshape.connector.store.jpa.util.Serializer.serializeProperties(Serializer.java:186)
at org.modeshape.connector.store.jpa.model.simple.SimpleJpaRepository$JpaNode.serializeProperties(SimpleJpaRepository.java:650)
at org.modeshape.connector.store.jpa.model.simple.SimpleJpaRepository$JpaNode.setProperty(SimpleJpaRepository.java:784)
at org.modeshape.graph.connector.map.MapRequestProcessor.process(MapRequestProcessor.java:397)

It appears the stream is being closed at: org.modeshape.connector.store.jpa.util.Serializer.serializeProperty(Serializer.java:315)