The multipart provider should allow a the temporary path for the ThresholdStorageProvider to be defined. This currently uses the java.io.tmpdir setting.

A new property, dev.resteasy.entity.tmp.dir or something similar, should be added to org.jboss.resteasy.spi.config.Options which would allow this to be overridden. This should also work in the org.jboss.resteasy.spi.EntityOutputStream.

The change would need to be in the org.jboss.resteasy.plugins.providers.multipart.Mime4JWorkaround.