AtomicInteger

Found this interesting class AtomicInteger that allows you to access primitives in a highly concurrent environment. I ran into an issue when I had to implement a throttling filter to allow only certain no of request in the app for a particular functionality to guarantee a certain level of QOS, my earlier code was

public class BackupThrottlingFilter implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        try {
            activeBackupRequests ++;
            if(activeBackupRequests > 50) {
                BackupFileUploadServlet.sendServiceUnavailableResponse((HttpServletResponse) response);
                return;
            }
            chain.doFilter(request, response);
        }
        finally {
            activeBackupRequests--;
        }
    }
    private static int activeBackupRequests;
}

Ran into an issue with this as its not synchronized so I had an option to use volatile or synchronized ,but synchronized is a killer as it would block but then I read about the new AtomicInteger class that allows you to abstract all this and allow highly concurrent operations on primitives


public class BackupThrottlingFilter implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        try {
            activeBackupRequests.incrementAndGet();
            if (activeBackupRequests.get() > 50) {
                BackupFileUploadServlet.sendServiceUnavailableResponse((HttpServletResponse) response);
                return;
            }
            chain.doFilter(request, response);
        } finally {
            activeBackupRequests.decrementAndGet();
        }
    }
    private static AtomicInteger activeBackupRequests = new AtomicInteger(0);
}