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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package async;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;
import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import async.Stockticker.Stock;
import async.Stockticker.TickListener;
public class AsyncStockServlet extends HttpServlet implements TickListener, AsyncListener{
private static final long serialVersionUID = 1L;
private static final Log log = LogFactory.getLog(AsyncStockServlet.class);
private static final ConcurrentLinkedQueue<AsyncContext> clients =
new ConcurrentLinkedQueue<>();
private static final AtomicInteger clientcount = new AtomicInteger(0);
public AsyncStockServlet() {
log.info("AsyncStockServlet created");
}
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
if (req.isAsyncStarted()) {
req.getAsyncContext().complete();
} else if (req.isAsyncSupported()) {
AsyncContext actx = req.startAsync();
actx.addListener(this);
resp.setContentType("text/plain");
clients.add(actx);
if (clientcount.incrementAndGet()==1) {
Stockticker ticker = (Stockticker) req.getServletContext().getAttribute(
AsyncStockContextListener.STOCK_TICKER_KEY);
ticker.addTickListener(this);
}
} else {
new Exception("Async Not Supported").printStackTrace();
resp.sendError(400,"Async is not supported.");
}
}
@Override
public void tick(Stock stock) {
for (AsyncContext actx : clients) {
try {
writeStock(actx, stock);
} catch (Exception e) {
// Ignore. The async error handling will deal with this.
}
}
}
public void writeStock(AsyncContext actx, Stock stock) throws IOException {
HttpServletResponse response = (HttpServletResponse)actx.getResponse();
PrintWriter writer = response.getWriter();
writer.write("STOCK#");//make client parsing easier
writer.write(stock.getSymbol());
writer.write("#");
writer.write(stock.getValueAsString());
writer.write("#");
writer.write(stock.getLastChangeAsString());
writer.write("#");
writer.write(String.valueOf(stock.getCnt()));
writer.write("\n");
writer.flush();
response.flushBuffer();
}
@Override
public void shutdown() {
// The web application is shutting down. Complete any AsyncContexts
// associated with an active client.
for (AsyncContext actx : clients) {
try {
actx.complete();
} catch (Exception e) {
// Ignore. The async error handling will deal with this.
}
}
}
@Override
public void onComplete(AsyncEvent event) throws IOException {
if (clients.remove(event.getAsyncContext()) && clientcount.decrementAndGet()==0) {
ServletContext sc = event.getAsyncContext().getRequest().getServletContext();
Stockticker ticker = (Stockticker) sc.getAttribute(
AsyncStockContextListener.STOCK_TICKER_KEY);
ticker.removeTickListener(this);
}
}
@Override
public void onError(AsyncEvent event) throws IOException {
event.getAsyncContext().complete();
}
@Override
public void onTimeout(AsyncEvent event) throws IOException {
event.getAsyncContext().complete();
}
@Override
public void onStartAsync(AsyncEvent event) throws IOException {
// NOOP
}
}
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