Netty中ChannelPoolHandler调用处理程序详解
作者：立小研先森
这篇文章主要介绍了Netty中ChannelPoolHandler调用处理程序详解,Netty 是基于 Java NIO 的异步事件驱动的网络应用框架,使用 Netty 可以快速开发网络应用,Netty 提供了高层次的抽象来简化 TCP 和 UDP 服务器的编程,但是你仍然可以使用底层的 API,需要的朋友可以参考下
ChannelPoolHandler调用处理程序
一、ChannelPoolHandler源码解析
public interface ChannelPoolHandler {
/**
* Channel信道被ChannelPool#release(Channel)或ChannelPool#release(Channel, Promise)方法
* 调用，并释放会ChannelPool连接池，
*/
void channelReleased(Channel ch) throws Exception;
/**
* Channel信道通过调用ChannelPool#acquire()或ChannelPool#acquire(Promise)方法获取
*/
void channelAcquired(Channel ch) throws Exception;
/**
* 在ChannelPool中创建Channel时将会被调用一次
*/
void channelCreated(Channel ch) throws Exception;
}
二、AbstractChannelPoolHandler源码解析
public abstract class AbstractChannelPoolHandler implements ChannelPoolHandler {
/**
* 无操作实现方法，可以被子类覆盖
*
*/
@Override
public void channelAcquired(@SuppressWarnings("unused") Channel ch) throws Exception {
// NOOP
}
/**
* 无操作实现方法，可以被子类覆盖
*/
@Override
public void channelReleased(@SuppressWarnings("unused") Channel ch) throws Exception {
// NOOP
}
}
AbstractChannelPoolHandler抽象类是ChannelPoolHandler的框架实现类，其实现了两个无任何操作的方法。
三、调用channelCreated方法
SimpleChannelPool#SimpleChannelPool构造函数中调用channelCreated方法
public SimpleChannelPool(Bootstrap bootstrap, final ChannelPoolHandler handler, ChannelHealthChecker healthCheck,
boolean releaseHealthCheck, boolean lastRecentUsed) {
this.handler = checkNotNull(handler, "handler");
this.healthCheck = checkNotNull(healthCheck, "healthCheck");
this.releaseHealthCheck = releaseHealthCheck;
// Clone the original Bootstrap as we want to set our own handler
this.bootstrap = checkNotNull(bootstrap, "bootstrap").clone();
this.bootstrap.handler(new ChannelInitializer<Channel>() {
@Override
protected void initChannel(Channel ch) throws Exception {
assert ch.eventLoop().inEventLoop();
//此处调用ChannelPoolHandler处理程序的创建Channel信道方法
handler.channelCreated(ch);
}
});
this.lastRecentUsed = lastRecentUsed;
}
四、获取Channel信道方法
SimpleChannelPool#notifyConnect方法中调用channelAcquired获取Channel信道方法
private void notifyConnect(ChannelFuture future, Promise<Channel> promise) {
Channel channel = null;
try {
if (future.isSuccess()) {
channel = future.channel();
//调用获取Channel信道方法
handler.channelAcquired(channel);
if (!promise.trySuccess(channel)) {
// Promise was completed in the meantime (like cancelled), just release the channel again
release(channel);
}
} else {
promise.tryFailure(future.cause());
}
} catch (Throwable cause) {
closeAndFail(channel, cause, promise);
}
}
五、释放Channel信道方法
SimpleChannelPool#releaseAndOffer和SimpleChannelPool#releaseAndOffer调用channelReleased释放Channel信道方法
private void releaseAndOfferIfHealthy(Channel channel, Promise<Void> promise, Future<Boolean> future) {
try {
if (future.getNow()) { //channel turns out to be healthy, offering and releasing it.
releaseAndOffer(channel, promise);
} else { //channel not healthy, just releasing it.
handler.channelReleased(channel);
promise.setSuccess(null);
}
} catch (Throwable cause) {
closeAndFail(channel, cause, promise);
}
}
private void releaseAndOffer(Channel channel, Promise<Void> promise) throws Exception {
if (offerChannel(channel)) {
handler.channelReleased(channel);
promise.setSuccess(null);
} else {
closeAndFail(channel, new ChannelPoolFullException(), promise);
}
}
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