JaxrsItemStoreResource.java
/*
* Copyright (c) 2017, 2019 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0, which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.glassfish.jersey.examples.sseitemstore.jaxrs;
import java.util.LinkedList;
import java.util.ListIterator;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.logging.Logger;
import javax.ws.rs.BadRequestException;
import javax.ws.rs.DefaultValue;
import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.HeaderParam;
import javax.ws.rs.InternalServerErrorException;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.ServiceUnavailableException;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.sse.OutboundSseEvent;
import javax.ws.rs.sse.Sse;
import javax.ws.rs.sse.SseBroadcaster;
import javax.ws.rs.sse.SseEventSink;
import org.glassfish.jersey.media.sse.SseFeature;
/**
* A resource for storing named items.
*
* @author Marek Potociar
*/
@Path("items")
public class JaxrsItemStoreResource {
private static final Logger LOGGER = Logger.getLogger(JaxrsItemStoreResource.class.getName());
private static final ReentrantReadWriteLock storeLock = new ReentrantReadWriteLock();
private static final LinkedList<String> itemStore = new LinkedList<>();
private static final AtomicReference<SseBroadcaster> BROADCASTER = new AtomicReference<>(null);
@Context
private Sse sse;
private static volatile long reconnectDelay = 0;
/**
* List all stored items.
*
* @return list of all stored items.
*/
@GET
@Produces(MediaType.TEXT_PLAIN)
public String listItems() {
try {
storeLock.readLock().lock();
return itemStore.toString();
} finally {
storeLock.readLock().unlock();
}
}
/**
* Receive & process commands sent by the test client that control the internal resource state.
* <p>
* Following is the list of recognized commands:
* <ul>
* <li><b>disconnect</b> - disconnect all registered event streams.</li>
* <li><b>reconnect now</b> - enable client reconnecting.</li>
* <li><b>reconnect <seconds></b> - disable client reconnecting.
* Reconnecting clients will receive a HTTP 503 response with
* {@value javax.ws.rs.core.HttpHeaders#RETRY_AFTER} set to the amount of
* milliseconds specified.</li>
* </ul>
*
* @param command command to be processed.
* @return message about processing result.
* @throws BadRequestException in case the command is not recognized or not specified.
*/
@POST
@Path("commands")
public String processCommand(String command) {
if (command == null || command.isEmpty()) {
throw new BadRequestException("No command specified.");
}
if ("disconnect".equals(command)) {
closeBroadcaster();
return "Disconnected.";
} else if ("reconnect ".length() < command.length() && command.startsWith("reconnect ")) {
final String when = command.substring("reconnect ".length());
try {
reconnectDelay = "now".equals(when) ? 0 : Long.parseLong(when);
return "Reconnect strategy updated: " + when;
} catch (NumberFormatException ignore) {
// ignored
}
}
throw new BadRequestException("Command not recognized: '" + command + "'");
}
/**
* TODO - rewrite Connect or re-connect to SSE event stream.
*
* @param lastEventId Value of custom SSE HTTP <tt>{@value SseFeature#LAST_EVENT_ID_HEADER}</tt> header.
* Defaults to {@code -1} if not set.
* @throws InternalServerErrorException in case replaying missed events to the reconnected output stream fails.
* @throws ServiceUnavailableException in case the reconnect delay is set to a positive value.
*/
@GET
@Path("events")
@Produces(MediaType.SERVER_SENT_EVENTS)
public void itemEvents(@HeaderParam(SseFeature.LAST_EVENT_ID_HEADER) @DefaultValue("-1") int lastEventId,
@Context SseEventSink eventSink) {
if (lastEventId >= 0) {
LOGGER.info("Received last event id :" + lastEventId);
// decide the reconnect handling strategy based on current reconnect delay value.
final long delay = reconnectDelay;
if (0 < delay) {
LOGGER.info("Non-zero reconnect delay [" + delay + "] - responding with HTTP 503.");
throw new ServiceUnavailableException(delay);
} else {
LOGGER.info("Zero reconnect delay - reconnecting.");
replayMissedEvents(lastEventId, eventSink);
}
}
getBroadcaster().register(eventSink);
}
private void replayMissedEvents(int lastEventId, SseEventSink eventSink) {
try {
storeLock.readLock().lock();
final int firstUnreceived = lastEventId + 1;
final int missingCount = itemStore.size() - firstUnreceived;
if (missingCount > 0) {
LOGGER.info("Replaying events - starting with id " + firstUnreceived);
final ListIterator<String> it = itemStore.subList(firstUnreceived, itemStore.size()).listIterator();
while (it.hasNext()) {
eventSink.send(createItemEvent(it.nextIndex() + firstUnreceived, it.next()));
}
} else {
LOGGER.info("No events to replay.");
}
} finally {
storeLock.readLock().unlock();
}
}
/**
* Add new item to the item store.
* <p>
* Invoking this method will fire 2 new SSE events - 1st about newly added item and 2nd about the new item store size.
*
* @param name item name.
*/
@POST
public void addItem(@FormParam("name") String name) {
// Ignore if the request was sent without name parameter.
if (name == null) {
return;
}
final int eventId;
try {
storeLock.writeLock().lock();
eventId = itemStore.size();
itemStore.add(name);
SseBroadcaster sseBroadcaster = getBroadcaster();
// Broadcasting an un-named event with the name of the newly added item in data
sseBroadcaster.broadcast(createItemEvent(eventId, name));
// Broadcasting a named "size" event with the current size of the items collection in data
final OutboundSseEvent event = sse.newEventBuilder().name("size").data(Integer.class, eventId + 1).build();
sseBroadcaster.broadcast(event);
} finally {
storeLock.writeLock().unlock();
}
}
private OutboundSseEvent createItemEvent(final int eventId, final String name) {
Logger.getLogger(JaxrsItemStoreResource.class.getName())
.info("Creating event id [" + eventId + "] name [" + name + "]");
return sse.newEventBuilder().id("" + eventId).data(String.class, name).build();
}
/**
* Get stored broadcaster or create a new one and store it.
*
* @return broadcaster instance.
*/
private SseBroadcaster getBroadcaster() {
SseBroadcaster sseBroadcaster = BROADCASTER.get();
if (sseBroadcaster == null) {
BROADCASTER.compareAndSet(null, sse.newBroadcaster());
}
return BROADCASTER.get();
}
/**
* Close currently stored broadcaster.
*/
private void closeBroadcaster() {
SseBroadcaster sseBroadcaster = BROADCASTER.getAndSet(null);
if (sseBroadcaster == null) {
return;
}
sseBroadcaster.close();
}
}