Has anyone tried Servlets 3.1 non blocking technique on tomcat?
The request from the browser seems to be waiting forever but when I run the server in debug mode, the call returns but still I don't see "Data read.." and "Data written.." in the logs.
Servlet:
@WebServlet(urlPatterns = "/asyncn", asyncSupported = true)
public class AsyncN extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void service(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException {
println("Before starting job");
final AsyncContext actx = request.startAsync();
actx.setTimeout(Long.MAX_VALUE);
actx.start(new HeavyTask(actx));
println("After starting job");
}
class HeavyTask implements Runnable {
AsyncContext actx;
HeavyTask(AsyncContext actx) {
this.actx = actx;
}
@Override
public void run() {
try {
Thread.currentThread().setName("Job-Thread-" + actx.getRequest().getParameter("job"));
// set up ReadListener to read data for processing
ServletInputStream input = actx.getRequest().getInputStream();
ReadListener readListener = new ReadListenerImpl(input, actx);
input.setReadListener(readListener);
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public static void println(String output) {
System.out.println("[" + Thread.currentThread().getName() + "]" + output);
}
}
Listeners:
public class ReadListenerImpl implements ReadListener {
private ServletInputStream input = null;
private AsyncContext actx = null;
// store the processed data to be sent back to client later
private Queue<String> queue = new LinkedBlockingQueue<>();
ReadListenerImpl(ServletInputStream input, AsyncContext actx) {
this.input = input;
this.actx = actx;
}
@Override
public void onDataAvailable() throws IOException {
println("Data is now available, starting to read");
StringBuilder sb = new StringBuilder();
int len = -1;
byte b[] = new byte[8];
// We need to check input#isReady before reading data.
// The ReadListener will be invoked again when
// the input#isReady is changed from false to true
while (input.isReady() && (len = input.read(b)) != -1) {
String data = new String(b, 0, len);
sb.append(data);
}
println("Data read: "+sb.toString());
queue.add(sb.toString());
}
@Override
public void onAllDataRead() throws IOException {
println("All Data read, now invoking write listener");
// now all data are read, set up a WriteListener to write
ServletOutputStream output = actx.getResponse().getOutputStream();
WriteListener writeListener = new WriteListenerImpl(output, queue, actx);
output.setWriteListener(writeListener);
}
@Override
public void onError(Throwable throwable) {
println("onError");
actx.complete();
throwable.printStackTrace();
}
public static void println(String output) {
System.out.println("[" + Thread.currentThread().getName() + "]" + output);
}
}
public class WriteListenerImpl implements WriteListener {
private ServletOutputStream output = null;
private Queue<String> queue = null;
private AsyncContext actx = null;
WriteListenerImpl(ServletOutputStream output, Queue<String> queue, AsyncContext actx) {
this.output = output;
this.queue = queue;
this.actx = actx;
}
@Override
public void onWritePossible() throws IOException {
println("Ready to write, writing data");
// write while there is data and is ready to write
while (queue.peek() != null && output.isReady()) {
String data = queue.poll();
//do some processing here with the data
try {
data = data.toUpperCase();
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
println("Data written: "+data);
output.print(data);
}
// complete the async process when there is no more data to write
if (queue.peek() == null) {
actx.complete();
}
}
@Override
public void onError(Throwable throwable) {
println("onError");
actx.complete();
throwable.printStackTrace();
}
public static void println(String output) {
System.out.println("[" + Thread.currentThread().getName() + "]" + output);
}
}
Sysout logs:
[http-nio-8080-exec-4]Before starting job
[http-nio-8080-exec-4]After starting job
Sysout logs (when I run the server in debug mode):
[http-nio-8080-exec-6]Before starting job
[http-nio-8080-exec-6]After starting job
[http-nio-8080-exec-6]All Data read, now invoking write listener
[http-nio-8080-exec-6]Ready to write, writing data
