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From Upayavira ...@upaya.co.uk>
Subject Re: Write binary data to output stream from flow
Date Fri, 18 Feb 2005 09:36:42 GMT
Bart Molenkamp wrote:
> 
>>-----Original Message-----
>>From: Upayavira [mailto:uv@upaya.co.uk]
>>Sent: Thursday, February 17, 2005 5:19 PM
>>To: dev@cocoon.apache.org
>>Subject: Re: Write binary data to output stream from flow
>>
>>Bart Molenkamp wrote:
>>
>>>Hi,
>>>
>>>Is it possible to write binary data to the HTTP response directly
> 
> from
> 
>>>the flow? I have an InputStream available in my flow, and I want to
>>>serve data from that stream directly to the HTTP response. E.g.
>>>
>>>cocoon.sendBinaryData(inputStream, "application/octet-stream");
>>>
>>>Or something similar.
>>>
>>>I solved it now by creating a SourceFactory and Source
> 
> implementation,
> 
>>>so that I can use a plain reader, but this feels a bit like
> 
> overkill.
> 
>>>The SourceFactory has to lookup the data from the database (that is
>>>where the data is for the input stream), and the URL contains the
>>>primary key to get the data from the database.
>>
>>To my knowledge there isn't a way to do this directly. But you could
>>place the inputstream into a request attribute or some such, and pick
>>that up from your source, rather than reading the database again.
>>
>>Am I understanding your question right?
>>
>>Regards, Upayavira
>  
> Hi Upayavira,
> 
> I don't know if I understood your answer. Maybe I'm not clear enough
> about my question, so I'll try again.
> 
> In my flowscript, I get a java.io.InputStream instance, and the content
> that I read from it can be sent to the user directly. The user thinks
> that it is downloading a file (which he is) but the source comes from a
> database (but the database is transparent due to OJB). In my case, I
> have a review object which can hold 0 or more downloaded files (files
> are evidence that support the result of the review):
> 
> ...
> review = ...; // get review from database trough OJB
> cocoon.sendPageAndWait("list-evidence.xml", 
>   {evidence: review.getEvidence()});
> 
> ...
> evidenceId = cocoon.request.get("evidenceId");
> evidence = review.getEvidenceById(evidenceId);
> evidenceDataStream = evidence.getInputStream();
> mimeType = evidence.getMimeType();
> 
> // now I want to serve the input stream to the user
> // e.g. something like
> cocoon.sendBinaryData(evidenceDataStream, mimeType);
> 
> How can I now read this input stream, and pass it's data to the output
> stream of a pipeline, in a simple way. Currently, I have an evidence
> source that I can lookup. The URL contains the ID of the review, and the
> ID of the evidence. Something like evidence://reviewid/evidenceid.txt

That is exactly what I took from what you were saying. And, as it 
currently stands, there is no way to send data other than via a 
pipeline. So, what I would say is:

cocoon.sendPage("my-binary-url", {"stream": evidenceDataStream, 
"mimeType": mimeType});

<map:match pattern="my-binary-url">
   <map:read src="evidence:"/>
</map:match>

Then, in your source, you can use o.a.c.components.flow.FlowHelper to 
get the stream and mimetype business objects, and have your source use 
them. I'm not up on this enough to give you exact details, but if I were 
to try to achieve this, this is probably how I would go about it.

Am I making sense now?

Regards, Upayavira

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