Question

I want to create and return a zip file from my server using JaxRS. I don’t think that I want to create an actual file on the server, if possible I would like to create the zip on the fly and pass that back to the client. If I create a huge zip file on the fly will I run out of memory if too many files are in the zip file?

Also I am not sure the most efficient way to do this. Here is what I was thinking but I am very rusty when it comes to input/output in java.

public Response getFiles() {

// These are the files to include in the ZIP file       
String[] filenames = // ... bunch of filenames

byte[] buf = new byte[1024];

try {
   // Create the ZIP file
   ByteArrayOutputStream baos= new ByteArrayOutputStream();
   ZipOutputStream out = new ZipOutputStream(new BufferedOutputStream(baos));

   // Compress the files
   for (String filename : filenames) {
       FileInputStream in = new FileInputStream(filename);

       // Add ZIP entry to output stream.
       out.putNextEntry(new ZipEntry(filename));

       // Transfer bytes from the file to the ZIP file
       int len;
       while ((len = in.read(buf)) > 0) {
         out.write(buf, 0, len);
       }
       // Complete the entry
       out.closeEntry();
       in.close();
   }

   // Complete the ZIP file
   out.close();

   ResponseBuilder response = Response.ok(out);  // Not a 100% sure this will work
   response.type(MediaType.APPLICATION_OCTET_STREAM);
   response.header("Content-Disposition", "attachment; filename=\"files.zip\"");
   return response.build();

} catch (IOException e) {       
}

}

Any help would be greatly appreciated.

Answer 1

There are two options:

1- Create ZIP in a temporal directory and then dump to client.

2- Use OutputStream from the Response to send zip directly to the client, when you are creating them.

But never use memory to create huge ZIP file.