Netty源码简析之初始化服务端Channel及Selector的注册过程
这里接着上文的《服务端Channel的创建》- https://blog.csdn.net/qq_28666081/article/details/102424327
初始化channel很简单，直接看如下代码：
// AbstractBootStrap.java
final ChannelFuture initAndRegister() {
Channel channel = null;
try {
channel = channelFactory.newChannel();
init(channel); // 初始化服务端channel，本文重点
..............
ChannelFuture regFuture = config().group().register(channel); // selector的注册过程，本文重点
1 初始化服务端Channel
void init(Channel channel) throws Exception {
// 第一步：初始化用户传入的自定义参数
final Map
synchronized (options) {
channel.config().setOptions(options);
}
final Map
synchronized (attrs) {
for (Entry
@SuppressWarnings("unchecked")
AttributeKey;
channel.attr(key).set(e.getValue());
}
}
ChannelPipeline p = channel.pipeline();
final EventLoopGroup currentChildGroup = childGroup;
final ChannelHandler currentChildHandler = childHandler;
final Entry
final Entry
synchronized (childOptions) {
currentChildOptions = childOptions.entrySet().toArray(newOptionArray(childOptions.size()));
}
synchronized (childAttrs) {
currentChildAttrs = childAttrs.entrySet().toArray(newAttrArray(childAttrs.size()));
}
// 第二步 创建连接记录器
p.addLast(new ChannelInitializer() {
@Override
public void initChannel(Channel ch) throws Exception {
final ChannelPipeline pipeline = ch.pipeline();
ChannelHandler handler = config.handler();
if (handler != null) {
pipeline.addLast(handler);
}
ch.eventLoop().execute(new Runnable() {
@Override
public void run() {
pipeline.addLast(new ServerBootstrapAcceptor(currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs));
}
});
}
});
}
总结：保存用户自定义的属性，并用这些属性创建一个连接记录器，连接记录器每次收到新连接，都会使用这些属性对新的连接做一些配置
2 Selector的注册过程
跟踪最上面代码ChannelFuture regFuture = config().group().register(channel)，然后最后可跟踪到如下：
public final void register(EventLoop eventLoop, final ChannelPromise promise) {
.....................
AbstractChannel.this.eventLoop = eventLoop; // 分析A点
if (eventLoop.inEventLoop()) {
register0(promise); // 分析B点
} else {
try {
eventLoop.execute(new Runnable() {
@Override
public void run() {
register0(promise);
}
});
} catch (Throwable t) {
.........................
}
从上面代码先看A点，A点是把eventLoop时间暂存起来，供后续使用
B点：这里进行了selector的真正注册过程，点进去看大致代码如下：
private void register0(ChannelPromise promise) {
try {
// check if the channel is still open as it could be closed in the mean time when the register
// call was outside of the eventLoop
if (!promise.setUncancellable() || !ensureOpen(promise)) {
return;
}
boolean firstRegistration = neverRegistered;
doRegister(); // 这里最终调用了jdk底层的NIO进行注册
neverRegistered = false;
registered = true;
// Ensure we call handlerAdded(...) before we actually notify the promise. This is needed as the
// user may already fire events through the pipeline in the ChannelFutureListener.
pipeline.invokeHandlerAddedIfNeeded();
safeSetSuccess(promise);
pipeline.fireChannelRegistered();
// Only fire a channelActive if the channel has never been registered. This prevents firing
// multiple channel actives if the channel is deregistered and re-registered.
if (isActive()) {
if (firstRegistration) {
pipeline.fireChannelActive();
} else if (config().isAutoRead()) {
// This channel was registered before and autoRead() is set. This means we need to begin read
// again so that we process inbound data.
//
// See https://github.com/netty/netty/issues/4805
beginRead();
}
}
} catch (Throwable t) {
// Close the channel directly to avoid FD leak.
closeForcibly();
closeFuture.setClosed();
safeSetFailure(promise, t);
}
}
few