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websocket-cometd源码阅读-初始化(二)
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常规配置
<!-- CometD Servlet -->
<servlet>
<servlet-name>cometd</servlet-name>
<!--<1>-->
<servlet-class>org.cometd.annotation.server.CometDServlet</servlet-class>
<!--liqiang todo 600000-->
<init-param>
<param-name>maxProcessing</param-name>
<param-value>600000</param-value>
</init-param>
<init-param>
<param-name>timeout</param-name>
<param-value>20000</param-value>
</init-param>
<init-param>
<param-name>interval</param-name>
<param-value>0</param-value>
</init-param>
<init-param>
<param-name>maxInterval</param-name>
<param-value>10000</param-value>
</init-param>
<init-param>
<param-name>handshakeReconnect</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>maxLazyTimeout</param-name>
<param-value>5000</param-value>
</init-param>
<init-param>
<param-name>long-polling.multiSessionInterval</param-name>
<param-value>2000</param-value>
</init-param>
<init-param>
<param-name>services</param-name>
<param-value>org.cometd.examples.ChatService</param-value>
</init-param>
<init-param>
<param-name>ws.cometdURLMapping</param-name>
<param-value>/cometd/*</param-value>
</init-param>
<!--容器启动时调用init方法初始化 而不是第一次调用时-->
<load-on-startup>1</load-on-startup>
<async-supported>true</async-supported>
</servlet>
<1>
通过ServletInit为切入点进行初始化
org.cometd.server.CometDServlet#init
@Override
public void init() throws ServletException {
try {
boolean export = false;
//可以通过ServletContext如果在别的地方自定义初始化 需要指定此值 比如自己根据spring容器初始化了
_bayeux = (BayeuxServerImpl)getServletContext().getAttribute(BayeuxServer.ATTRIBUTE);
if (_bayeux == null) {
export = true;
//初始化
_bayeux = newBayeuxServer();
//这里主要是设置Servlet参数到_bayeux 供后续初始化使用
// Transfer all servlet init parameters to the BayeuxServer implementation
for (String initParamName : Collections.list(getInitParameterNames())) {
_bayeux.setOption(initParamName, getInitParameter(initParamName));
}
//添加ServletContext到_bayeux
// Add the ServletContext to the options
_bayeux.setOption(ServletContext.class.getName(), getServletContext());
}
//调用start进行组件初始化<2>
_bayeux.start();
if (export) {
//设置到Attribute
getServletContext().setAttribute(BayeuxServer.ATTRIBUTE, _bayeux);
}
} catch (Exception x) {
throw new ServletException(x);
}
}
<2>
org.cometd.server.BayeuxServerImpl#doStart
@Override
protected void doStart() throws Exception {
//<3>初始化内置的渠道
initializeMetaChannels();
//<4>初始化消息序列化转换器
initializeJSONContext();
//<5>初始化Transport
initializeServerTransports();
//如果线程池为空 创建线程池
if (_executor == null) {
//<7>
_executor = new MarkedReference<>(newExecutor(), true);
}
addBean(_executor.getReference());
//如果Schedule为空 创建Scheduler
if (_scheduler == null) {
_scheduler = new MarkedReference<>(newScheduler(), true);
}
addBean(_scheduler.getReference());
//配置获得validateMessageFields 默认为true 是否进行消息格式校验
_validation = getOption(VALIDATE_MESSAGE_FIELDS_OPTION, true);
//配置获得broadcastToPublisher 默认为true 此消息是否广播到发布者,比如都订阅了同一个渠道,是否广播给自己
_broadcastToPublisher = getOption(BROADCAST_TO_PUBLISHER_OPTION, true);
super.doStart();
long defaultSweepPeriod = 997;
//获得配置的sweepPeriodOption 会话扫描周期检查会话是否需要移除 默认997 毫秒单位
long sweepPeriodOption = getOption(SWEEP_PERIOD_OPTION, defaultSweepPeriod);
if (sweepPeriodOption < 0) {
sweepPeriodOption = defaultSweepPeriod;
}
long sweepPeriod = sweepPeriodOption;
//开启session检查,检查是否需要剔除
schedule(new Runnable() {
@Override
public void run() {
//并行执行asyncSweep的四个任务 执行完后指定周期后 开启下一轮 实现了定时任务效果
asyncSweep().whenComplete((r, x) -> schedule(this, sweepPeriod));
}
}, sweepPeriod);
}
<3>
org.cometd.server.BayeuxServerImpl#initializeMetaChannels
protected void initializeMetaChannels() {
//握手<8>
createChannelIfAbsent(Channel.META_HANDSHAKE);
//续约连接
createChannelIfAbsent(Channel.META_CONNECT);
//订阅渠道
createChannelIfAbsent(Channel.META_SUBSCRIBE);
//取消订阅
createChannelIfAbsent(Channel.META_UNSUBSCRIBE);
//断开连接
createChannelIfAbsent(Channel.META_DISCONNECT);
}
<4>
org.cometd.server.BayeuxServerImpl#initializeJSONContext
protected void initializeJSONContext() throws Exception {
//默认通过 option jsonContext去获取
Object option = getOption(AbstractServerTransport.JSON_CONTEXT_OPTION);
if (option == null) {
//未配置则获取默认的
_jsonContext = new JettyJSONContextServer();
} else {
//如果我们有配置的是class全名称
if (option instanceof String) {
Class<?> jsonContextClass = Thread.currentThread().getContextClassLoader().loadClass((String)option);
if (JSONContextServer.class.isAssignableFrom(jsonContextClass)) {
_jsonContext = (JSONContextServer)jsonContextClass.getConstructor().newInstance();
} else {
throw new IllegalArgumentException("Invalid " + JSONContextServer.class.getName() + " implementation class");
}
} else if (option instanceof JSONContextServer) {//如果是context对象
_jsonContext = (JSONContextServer)option;
} else {
throw new IllegalArgumentException("Invalid " + JSONContextServer.class.getName() + " implementation class");
}
}
_options.put(AbstractServerTransport.JSON_CONTEXT_OPTION, _jsonContext);
}
<5>
org.cometd.server.BayeuxServerImpl#initializeServerTransports
protected void initializeServerTransports() {
if (_transports.isEmpty()) {
//初始化Transport 没重定义则创建默认 指定了则创建指定的 注:反射创建 会传入bayeux
String option = (String)getOption(TRANSPORTS_OPTION);
if (option == null) {
//未定义则初始化处理websocket 和长轮询的Transport处理器 JSONP的处理器
// Order is important, see #findHttpTransport()
//<6>
ServerTransport transport = newWebSocketTransport();
if (transport != null) {
addTransport(transport);
}
addTransport(newJSONTransport());
addTransport(new JSONPTransport(this));
} else {
//如果有进行类的全名称配置 根据累的全名称创建
for (String className : option.split(",")) {
ServerTransport transport = newServerTransport(className.trim());
if (transport != null) {
addTransport(transport);
}
}
if (_transports.isEmpty()) {
throw new IllegalArgumentException("Option '" + TRANSPORTS_OPTION +
"' does not contain a valid list of server transport class names");
}
}
}
//如果没有配置_allowedTransports 将transport加入到 _allowedTransports//liqiangtodo 暂时不晓得干嘛的
if (_allowedTransports.isEmpty()) {
String option = (String)getOption(ALLOWED_TRANSPORTS_OPTION);
if (option == null) {
_allowedTransports.addAll(_transports.keySet());
} else {
for (String transportName : option.split(",")) {
if (_transports.containsKey(transportName)) {
_allowedTransports.add(transportName);
}
}
if (_allowedTransports.isEmpty()) {
throw new IllegalArgumentException("Option '" + ALLOWED_TRANSPORTS_OPTION +
"' does not contain at least one configured server transport name");
}
}
}
//逐个调用transport init方法完成Transport的初始化 Transport 内部的相关参数自定义配置可以通过Option拿到
List<String> activeTransports = new ArrayList<>();
for (String transportName : _allowedTransports) {
ServerTransport serverTransport = getTransport(transportName);
if (serverTransport instanceof AbstractServerTransport) {
//调用init方法进行初始化
((AbstractServerTransport)serverTransport).init();
//加入到已激活的transpor
activeTransports.add(serverTransport.getName());
}
}
if (_logger.isDebugEnabled()) {
_logger.debug("Active transports: {}", activeTransports);
}
}
<6>
org.cometd.server.BayeuxServerImpl#newWebSocketTransport
private ServerTransport newWebSocketTransport() {
try {
ClassLoader loader = Thread.currentThread().getContextClassLoader();
//加载服务端websoket组件 websocket组件
loader.loadClass("javax.websocket.server.ServerContainer");
//初始化websoketTransport
String transportClass = "org.cometd.server.websocket.javax.WebSocketTransport";
ServerTransport transport = newServerTransport(transportClass);
if (transport == null) {
_logger.info("JSR 356 WebSocket classes available, but " + transportClass +
" unavailable: JSR 356 WebSocket transport disabled");
}
return transport;
} catch (Exception x) {
return null;
}
}
<7>
org.cometd.server.BayeuxServerImpl#newExecutor
private Executor newExecutor() {
String name = _name + "-Executor";
//默认线程大小为128
int maxThreads = (int)getOption(EXECUTOR_MAX_THREADS, 128);
QueuedThreadPool executor = new QueuedThreadPool(maxThreads, 0);
executor.setName(name);
executor.setReservedThreads(0);
return executor;
}
<8>
org.cometd.server.BayeuxServerImpl#createChannelIfAbsent
@Override
public MarkedReference<ServerChannel> createChannelIfAbsent(String channelName, Initializer... initializers) {
ChannelId channelId;
boolean initialized = false;
//尝试根据channelName获取 判断是否存在
ServerChannelImpl channel = _channels.get(channelName);
if (channel == null) {
// Creating the ChannelId will also normalize the channelName.
//尝试通过处理过的channelId获取
channelId = new ChannelId(channelName);
String id = channelId.getId();
if (!id.equals(channelName)) {
channelName = id;
channel = _channels.get(channelName);
}
} else {
channelId = channel.getChannelId();
}
//表示没有被初始化
if (channel == null) {
//新建一个channel
ServerChannelImpl candidate = new ServerChannelImpl(this, channelId);
//放入_channels
channel = _channels.putIfAbsent(channelName, candidate);
if (channel == null) {
// My candidate channel was added to the map, so I'd better initialize it
channel = candidate;
if (_logger.isDebugEnabled()) {
_logger.debug("Added channel {}", channel);
}
try {
//通知 Initializer实现 可以对ServerChannelImpl做自定义配置
for (Initializer initializer : initializers) {
notifyConfigureChannel(initializer, channel);
}
//调用listeners中ChannelListener的configureChannel方法可以对channel进行自定义配置
for (BayeuxServer.BayeuxServerListener listener : _listeners) {
if (listener instanceof ServerChannel.Initializer) {
notifyConfigureChannel((Initializer)listener, channel);
}
}
} finally {
channel.initialized();
}
//调用listeners中ChannelListener的channelAdded表示已经被初始化
for (BayeuxServer.BayeuxServerListener listener : _listeners) {
if (listener instanceof BayeuxServer.ChannelListener) {
notifyChannelAdded((ChannelListener)listener, channel);
}
}
initialized = true;
}
} else {
channel.resetSweeperPasses();
// Double check if the sweeper removed this channel between the check at the top and here.
// This is not 100% fool proof (e.g. this thread is preempted long enough for the sweeper
// to remove the channel, but the alternative is to have a global lock)
_channels.putIfAbsent(channelName, channel);
}
// Another thread may add this channel concurrently, so wait until it is initialized
channel.waitForInitialized();
return new MarkedReference<>(channel, initialized);
}
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