InputStream is = request.getSession().getServletContext().getResourceAsStream("/WEB-INF/swdjzbg.png");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
int len = 1024;
byte tmp [] = new byte[len];
int i ;
while((i=is.read(tmp, 0, len))>0){
baos.write(tmp, 0, i);
}
byte imgs[] = baos.toByteArray();