Problem in creating zip file on weblogic server

When i run following code on a tomcat server on local machine it rus fine & gives a correct zip file but when I run this on weblogic server then it gives error as

error:[c:\Documents & settings\mt1\local settings\temporary internet files\myzipfile[1].zip]": start of central directory not found. Zip file corrupt.
Possible error: Zip file error

Can anybody please help me in this?

That will probably already solve your problem. When read(byte[]) returns 0 that doesn't mean all data is read. It means there's currently no data available. -1 is the only value that indicates that you're done reading.

Also, you can remove this line:
reader.read(buffer) will re-fill the existing array. It's possible (likely even) that one or more reads do not overwrite all old data, but you know that all values from 0 to bytesRead (exclusive) are filled with new data, and this is exactly the portion you then write. In other words, all you're doing is create another array where no new array is necessary.

I did above changes. its still not working. It seems there is problem with the header of the zip file. Can anybody help to resolve exactly?

If this is a JSP, make sure that absolutely no output is sent to the response before you use your code. That includes line breaks outside of JSP directives / tags. Even enters between your import directives will already be sent to the response.