Marius <marius.dan...@gmail.com> writes: > On Feb 26, 11:50 am, Jeppe Nejsum Madsen <je...@ingolfs.dk> wrote: >> Hi, >> >> I need to create a response that downloads a file. The file is >> generated by a 3rd party api that takes an output stream as the target >> for the file. As the file can be rather large, I would like to stream >> this file directly to the client. >> >> I've looked at StreamingResponse, but this seem to require something >> akin to an input stream. >> >> As there a way to generate a response with direct access to the output >> stream? > > > No. IMO this would bring serious problems related with "committed > response" if people will start writing directly into servlet's > response output stream.
Normally, yes. But I think there are special cases that may warrant this and I tend to think this is one of them :-) > But you should be able to bridge the outputstream needed by that > library and the "inputstream" from the StreamingResponse ( which takes > a structural type not really an InputStream) through mechanisms > similar with Pipes. But unless I create a new thread, I'll still end up with the entire file in memory. Ie the call to the library's write method must return before the streaming response can be created and thus the file contents must be stored somewhere. > You could also build your own OutputStream that also has def read(buf: > Array[Byte]): Int. Thus your library will write stuff in your > OutputStream, you would then buffer the data and wait for that data to > be drained by the servlet's input stream. A simple producer/consumer > approach. If I create a new thread I could probably use PipedOutputStream which does this already. But still the file contents will be copied twice: 1) >From pipe output to pipe input, 2) from pipe input to response output So the thread creation/scheduling and the two times file copying could be avoided by writing directly to the output stream. But I agree this would have to be special cased somehow. It's not an urgent issue atm, but I'll try to see if some clean solution can be implemented. /Jeppe -- You received this message because you are subscribed to the Google Groups "Lift" group. To post to this group, send email to lift...@googlegroups.com. To unsubscribe from this group, send email to liftweb+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/liftweb?hl=en.
