Streams but no IO allowed

[Leo Madrid]

Hi Guys,

I'm hoping some of you can help me with this issue which I've been trying to solve.
This is for a jsp-servlet web app using java 1.5. This is the scenario :

- I need to create 3 csv files
- I need to compress these 3 csv files into one zip file
- I need to return the zip file in the response back to the user

Here is the caveat, no writing-reading from the disk allowed. Meaning that the csv and zip files can't be stored or read from the disk. Everything must be created in memory at runtime(and of course disposed of when the servlet is done).

I know there are dozens of examples on line unfortunately almost all are disk read-write based. Any help would be appreciated.

[Jeff Verdegan]

Look into ByteArrayInputStream and ByteArrayOutputStream. Those let you read and write bytes against arrays in memory.

[Leo Madrid]

Thanks Jeff for your response.

But every example I've seen on ByteArrayOutputStream includes a file that already exists on the disk. Perhaps my question was too vague. Basically, I'd like to be able to do code snippet ONE without having to actually write "MyFileName" to the disk. Then I'd like to perform code snippet TWO and send "MyFileName" (which of course only exists in memory) in the response.

String text = "Wouldnt you like to be a pepper too?";
File MyFileName = new File("MyFile.txt");
Writer output = new BufferedWriter(new FileWriter(file));

InputStream inputStream = new FileInputStream(MyFileName);
        
byte[] buffer = new byte[8192];
ByteArrayOutputStream baos = new ByteArrayOutputStream(); 

int bytesRead;
while (  (bytesRead = inputStream.read(buffer)) != -1)
   baos.write(buffer, 0, bytesRead);

	    
response.setContentType("application/zip");
response.addHeader("Content-Disposition", "attachment; filename=Invoice.zip");
		
byte[] outBuf = baos.toByteArray();
ServletOutputStream stream = response.getOutputStream();
stream.write(outBuf);

[Jeff Verdegan]

Leo Madrid wrote:Thanks Jeff for your response.

But every example I've seen on ByteArrayOutputStream includes a file that already exists on the disk

You don't need a file

Writer output = new BufferedWriter(new OutputStreamWriter(new ByteArrayOutputStream(/* optional initial size */)));

[Rob Spoor]

Jeff Verdegan wrote:

ByteArrayOutputStream baos = new ByteArrayOutputStream(/* optional initial size */);
Writer output = new BufferedWriter(new OutputStreamWriter(baos));

Fixed that for you. Without a reference to the ByteArrayOutputStream, you can't retrieve its contents, now can you?

[Jeff Verdegan]

Rob Spoor wrote:

Jeff Verdegan wrote:

ByteArrayOutputStream baos = new ByteArrayOutputStream(/* optional initial size */);
Writer output = new BufferedWriter(new OutputStreamWriter(baos));

Fixed that for you. Without a reference to the ByteArrayOutputStream, you can't retrieve its contents, now can you?

I, um, did that on purpose to encourage the OP to read the docs. Yeah, that's it.

[Rob Spoor]