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Streaming audio file directly from blob

So I am working on this project where I want to store an audio file in a LARGEBLOB on a database, the size of the file is limited to about 10MB, and be able to load the data through a java servlet that allows for playing of the media file.
Most of the sources I have been able to find suggests storing it locally, however, I want to avoid this solution based on the fact that I'd like to rebuild the website somewhere completely different and not have to rely on the folder structure to be the same.
The issues that I am encountering area mainly that the web browser misinterprets the binary data provided by the servlet. It manages to retrieve that it is an audio file of some sort, however; it is unable to determine the type of audio file, which leads me to believe that the servlet is either not providing enough data, or that I am not doing enough to instruct the web browser on how to play the file.
For example, if I have a file audio.mp3 which I have uploaded to the database into a table Tracks and stored in a column TrackFile. Assuming the query of selecting the right song from the table, what data would the servlet need to provide in order for the browser to play the file when accessing the servlet. Currently when I load the servlet, the browser seems to assume that the type is audio/mpeg instead of audio/mp3. The content currently delivered by the servlet also looks something like this:
response.setHeader("Content-Type", this.getServletContext().getMimeType(t.getTrackName() + '.' + t.getFileType()));
response.setHeader("Content-Length", String.valueOf(t.getTrackData().length));
response.setHeader("Content-Disposition", "inline; filename=\"" + t.getTrackName() + '.' + t.getFileType() + "\"");
response.getOutputStream().write(t.getTrackData());
where t is an object which holds all the data which can be retrieved from the database table about a specific track. The method getTrackData() returns a byte[] with contents of the column TrackFile in it. The source of this method is: link, although I adapted it in order to make it work with audio files, although it doesn't.
Are there any obvious things that I should have caught onto based on the fact that I can't get it to play back the file or is what I want to achieve generally impossible so to say?

SDMX-ML: SAS libname XML

Eurostat data can be downloaded via a REST API. The response format of the API is a XML file formatted according to the SDMX-ML standard. With SAS, very conveniently, one can access XML files with the libname statement and the XML or XMLv2 engine.
Currently, I am using the xmlv2 engine together with the automap= option to generate an xmlmap to access the data. It works. But the resulting SAS data sets are very unstructured, and for another data set to be downloaded the data structure might change. Also the request might depend on the DSD-file that Eurostat provides for each database item within a different XML file.
Here comes the code:
%let path = /your/working/directory/;
filename map "&path.map.txt";
filename resp "&path.resp.txt";
proc http
URL="http://ec.europa.eu/eurostat/SDMX/diss-web/rest/data/cdh_e_fos/..PC.FOS1.BE/?startperiod=2005&endPeriod=2011"
METHOD="GET"
OUT=resp;
run;quit;
libname resp XMLv2 automap=REPLACE xmlmap=map;
proc datasets;
copy out=WORK in=resp;
run;quit;
With the code above, you can view all downloaded data in your WORK library. Its a mess.
To download another time series change parameters of the URL according to Eurostat's description.
So here is my question
Is there a way to easily generate a xmlmap from a call to the DSD file so that the data are stored in a well structured way?
As the SDMX-ML standard is widely used in public institutions such as the ECB, Eurostat, OECD... I am wondering if somebody has implemented requests to the databases, already. I know about the tool from Banca Italia which uses a javaObject. However, I was wondering if there might be a solution without the javaObject.

Capture generated output file path and name using CSSDK

We are in the process of converting over to using the XSLT compiler for page generation. I have a Xalan Java extention to exploit the CSSDK and capture some meta data we have stored in the Extended Attributes for output to the page. No problems in getting the EA's rendered to the output file.
The problem is that I don't know how to dynamically capture the file path and name of the output file.
So just as POC, I have the CSVPath hard coded to the output file in my Java extension. Here's a code sample:
CSSimpleFile sourceFile = (CSSimpleFile)client.getFile(new CSVPath("/some-path-to-the-output.jsp"));
Can someone point me in the CSSDK to where I could capture the output file?

I found the answer.
First, get or create your CSClient. You can use the examples provided in the cssdk/samples. I tweaked one so that I captured the CSClient in the method getClientForCurrentUser(). Watch out for SOAP vs Java connections. In development, I was using a SOAP connection and for the make_toolkit build, the Java connection was required for our purposes.
Check the following snippet. The request CSClient is captured in the static variable client.
CSSimpleFile sourceFile = (CSSimpleFile)client.getFile(new CSVPath(XSLTExtensionContext.getContext().getOutputDirectory().toString() + "/" + XSLTExtensionContext.getContext().getOutputFileName()));

Writing to a PDF from inside a GAE app

I need to read several megabytes (raw text strings) out of my GAE Datastore and then write them all to a new PDF file, and then make the PDF file available for the user to download.
I am well aware of the sandbox restrictions that prevent you from writing to the file system. I am wondering if there is a crafty way of creating a PDF in-memory (or a combo of memory and the blobstore) and then storing it somehow so that the client-side (browser) can actually pull it down as a file and save it locally.
This is probably a huge stretch, but my only other option is to farm this task out to a non-GAE server, which I would like to avoid at all cost, even if it takes a lot of extra development on my end. Thanks in advance.

You can definitely achieve your use case using GAE itself. Here are the steps that you should follow at a high level:
Download the excellent iText library, which is a Java library to work with PDFs. First build out your Java code to generate the PDF content. Check out various examples at : http://itextpdf.com/book/toc.php
Since you cannot write to a file directly, you need to generate your PDF content in bytes and then write a Servlet which will act as a Download Servlet. The Servlet will use the Response object to open a stream, manipulate the Mime Headers (filename, filetype) and write the PDF contents to the stream. A browser will automatically present a download option when you do that.
Your Download Servlet will have high level code that looks like this:
public class DownloadPDF extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
//Extract some request parameters, fetch your data and generate your document
String fileName = "<SomeFileName>.pdf";
res.setContentType("application/pdf");
res.setHeader("Content-Disposition", "attachment;filename=\"" + fileName + "\"");
writePDF(<SomeObjectData>, res.getOutputStream());
}
}
}
Remember the writePDF method above is your own method, where you use iText libraries Document and other classes to generate the data and write it ot the outputstream that you have passed in the second parameter.

While I'm not aware of the PDF generation on Google App Engine and especially in Java, but once you have it you can definitely store it and later serve it.
I suppose the generation of the PDF will take more than 30 seconds so you will have to consider using Task Queue Java API for this process.
After you have the file in memory you can simply write it to the Blobstore and later serve it as a regular blob. In the overview you will find a fully functional example on how to upload, write and serve your binary data (blobs) on Google App Engine.

I found a couple of solutions by googling. Please note that I have not actually tried these libraries, but hopefully they will be of help.
PDFJet (commercial)
Write a Google Drive document and export to PDF

jaudiotagger library - creating m4a tag reading file

I'm new to Java enviroment, recently I've been trying to create a simple mp3 tag reading file. Everything went ok until I tried to read tags from m4a file. After reading all API documentation and examples sadly I have still no idea how to scrypt m4a tag reading method. Could you please give me an example of working m4a tag reading method, so I could learn from it, with some simple clarification. I'd be very pleased.

Something like this:
AudioFile f = AudioFileIO.read("test.mp4");
Tag tag = f.getTag();
Iterator<TagField> i = tag.getFields()
while(i.hasNext()) {
System.out.println(i.next());
}
The problem you might be having is that mp3 can be read either using the generic interface which is the same for all formats (the above code is using that) or using the mp3 specific interface that deals with ID3 frames. So if you did mp3s using that interface then the code for the other formats is very different.