org.jivesoftware.smack.PacketCollector Maven / Gradle / Ivy
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/**
* $RCSfile$
* $Revision: 12509 $
* $Date: 2011-06-18 13:18:03 -0500 (Sat, 18 Jun 2011) $
*
* Copyright 2003-2007 Jive Software.
*
* All rights reserved. Licensed 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 org.jivesoftware.smack;
import org.jivesoftware.smack.filter.PacketFilter;
import org.jivesoftware.smack.packet.Packet;
import java.util.LinkedList;
/**
* Provides a mechanism to collect packets into a result queue that pass a
* specified filter. The collector lets you perform blocking and polling
* operations on the result queue. So, a PacketCollector is more suitable to
* use than a {@link PacketListener} when you need to wait for a specific
* result.
*
* Each packet collector will queue up a configured number of packets for processing before
* older packets are automatically dropped. The default number is retrieved by
* {@link SmackConfiguration#getPacketCollectorSize()}.
*
* @see Connection#createPacketCollector(PacketFilter)
* @author Matt Tucker
*/
public class PacketCollector {
/**
* Max number of packets that any one collector can hold. After the max is
* reached, older packets will be automatically dropped from the queue as
* new packets are added.
*/
private int maxPackets = SmackConfiguration.getPacketCollectorSize();
private PacketFilter packetFilter;
private LinkedList resultQueue;
private Connection conection;
private boolean cancelled = false;
/**
* Creates a new packet collector. If the packet filter is null, then
* all packets will match this collector.
*
* @param conection the connection the collector is tied to.
* @param packetFilter determines which packets will be returned by this collector.
*/
protected PacketCollector(Connection conection, PacketFilter packetFilter) {
this.conection = conection;
this.packetFilter = packetFilter;
this.resultQueue = new LinkedList();
}
/**
* Creates a new packet collector. If the packet filter is null, then
* all packets will match this collector.
*
* @param conection the connection the collector is tied to.
* @param packetFilter determines which packets will be returned by this collector.
* @param maxSize the maximum number of packets that will be stored in the collector.
*/
protected PacketCollector(Connection conection, PacketFilter packetFilter, int maxSize) {
this(conection, packetFilter);
maxPackets = maxSize;
}
/**
* Explicitly cancels the packet collector so that no more results are
* queued up. Once a packet collector has been cancelled, it cannot be
* re-enabled. Instead, a new packet collector must be created.
*/
public void cancel() {
// If the packet collector has already been cancelled, do nothing.
if (!cancelled) {
cancelled = true;
conection.removePacketCollector(this);
}
}
/**
* Returns the packet filter associated with this packet collector. The packet
* filter is used to determine what packets are queued as results.
*
* @return the packet filter.
*/
public PacketFilter getPacketFilter() {
return packetFilter;
}
/**
* Polls to see if a packet is currently available and returns it, or
* immediately returns null if no packets are currently in the
* result queue.
*
* @return the next packet result, or null if there are no more
* results.
*/
public synchronized Packet pollResult() {
if (resultQueue.isEmpty()) {
return null;
}
else {
return resultQueue.removeLast();
}
}
/**
* Returns the next available packet. The method call will block (not return)
* until a packet is available.
*
* @return the next available packet.
*/
public synchronized Packet nextResult() {
// Wait indefinitely until there is a result to return.
while (resultQueue.isEmpty()) {
try {
wait();
}
catch (InterruptedException ie) {
// Ignore.
}
}
return resultQueue.removeLast();
}
/**
* Returns the next available packet. The method call will block (not return)
* until a packet is available or the timeout has elapased. If the
* timeout elapses without a result, null will be returned.
*
* @param timeout the amount of time to wait for the next packet (in milleseconds).
* @return the next available packet.
*/
public synchronized Packet nextResult(long timeout) {
// Wait up to the specified amount of time for a result.
if (resultQueue.isEmpty()) {
long waitTime = timeout;
long start = System.currentTimeMillis();
try {
// Keep waiting until the specified amount of time has elapsed, or
// a packet is available to return.
while (resultQueue.isEmpty()) {
if (waitTime <= 0) {
break;
}
wait(waitTime);
long now = System.currentTimeMillis();
waitTime -= (now - start);
start = now;
}
}
catch (InterruptedException ie) {
// Ignore.
}
// Still haven't found a result, so return null.
if (resultQueue.isEmpty()) {
return null;
}
// Return the packet that was found.
else {
return resultQueue.removeLast();
}
}
// There's already a packet waiting, so return it.
else {
return resultQueue.removeLast();
}
}
/**
* Processes a packet to see if it meets the criteria for this packet collector.
* If so, the packet is added to the result queue.
*
* @param packet the packet to process.
*/
protected synchronized void processPacket(Packet packet) {
if (packet == null) {
return;
}
if (packetFilter == null || packetFilter.accept(packet)) {
// If the max number of packets has been reached, remove the oldest one.
if (resultQueue.size() == maxPackets) {
resultQueue.removeLast();
}
// Add the new packet.
resultQueue.addFirst(packet);
// Notify waiting threads a result is available.
notifyAll();
}
}
}