How to convert a InputStream to ZIP format?

Question

I am having a InputStream Object which is actually a zip file. I want to change it back to zip file and save it. I am using DWR's FileTransfer class object to receive the uploaded data from client.

FileTransfer have 3 methods, getInputStream() is one of them. It returns InputStream from FileTransfer object.

In my case, fileTransfer object holds zip file and as well as InputStream object too. I have done, lot of searches in google. But i am not able to find one example, that illustrates InputStream to zip conversion.

Update

String zipName = file.getName();
String zipType = file.getMimeType();
InputStream zipStream = file.getInputStream();
ZipInputStream zis = new ZipInputStream(zipStream);
System.out.println("File Name: "+zipName+"\n"+"File Type: "+zipType);
int c;
File f2 = new File(DATA_STORE_LOC+dat+".zip");
path.setPath2(DATA_STORE_LOC+dat+".zip");
FileOutputStream fos = new FileOutputStream(f2);
ZipOutputStream zos = new ZipOutputStream(fos);
c = zis.read();
System.out.println(c);
while ((c = zis.read(BUFFER)) != -1) {
zos.write(BUFFER, 0, c);
}
zos.close();
zis.close();

I tried this code, by thought of a typical file copy program. I know it is false, just tried. It gives me java.util.zip.ZipException: ZIP file must have at least one entry.

Any suggestion would be really appreciative!!!!!

Answer 1

If your input is a an InputStream from a zip file and your desired output is still a zip file with the same contents, you're just doing a file copy operation and shouldn't have to worry about zip at all. You just need to read from the InputStream and write to a FileOutputStream, more or less as you're doing, but without worrying about wrapping either stream in a zip-aware stream.

ZipInputStream is useful if you have to extract the contents of the zip file as separate files, i.e., to programmatically unzip. And on the other side, ZipOutputStream is used if your have the contents and need to combine them into a zip file.