一、前言
上篇博客介绍了服务端的启动源码,这篇就开始介绍客户端
二、源码分析
首先贴上客户端的简单代码~
public class SocketClient {
public static void main(String[] args) throws InterruptedException {
EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class).handler(new LoggingHandler(LogLevel.INFO))
.handler(new SocketClientInitializer());
ChannelFuture channelFuture = bootstrap.connect("localhost", 7878).sync();
channelFuture.channel().closeFuture().sync();
} finally {
eventLoopGroup.shutdownGracefully();
}
}
}
设置group和server端不同的是,这里这设置一个group
public B group(EventLoopGroup group) {
if (group == null) {
throw new NullPointerException("group");
}
if (this.group != null) {
throw new IllegalStateException("group set already");
}
this.group = group;
return (B) this;
}
设置channel
public B channel(Class<? extends C> channelClass) {
if (channelClass == null) {
throw new NullPointerException("channelClass");
}
// server端使用的是ReflectiveChannelFactory
// 最后newChannel()后面也是通过反射来实现的了
return channelFactory(new BootstrapChannelFactory<C>(channelClass));
}
设置handler
@SuppressWarnings("unchecked")
public B handler(ChannelHandler handler) {
if (handler == null) {
throw new NullPointerException("handler");
}
this.handler = handler;
return (B) this;
}
接着就是核心代码连接了
public ChannelFuture connect(String inetHost, int inetPort) {
return connect(new InetSocketAddress(inetHost, inetPort));
}
public ChannelFuture connect(SocketAddress remoteAddress) {
if (remoteAddress == null) {
throw new NullPointerException("remoteAddress");
}
validate();
return doConnect(remoteAddress, localAddress());
}
// 这部分代码和server绑定类似
private ChannelFuture doConnect(final SocketAddress remoteAddress, final SocketAddress localAddress) {
// 初始化和注册channel
final ChannelFuture regFuture = initAndRegister();
// 获取channel
final Channel channel = regFuture.channel();
if (regFuture.cause() != null) {
return regFuture;
}
final ChannelPromise promise = channel.newPromise();
if (regFuture.isDone()) {
doConnect0(regFuture, channel, remoteAddress, localAddress, promise);
} else {
// 为future添加一个监听器
regFuture.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
doConnect0(regFuture, channel, remoteAddress, localAddress, promise);
}
});
}
return promise;
}
final ChannelFuture initAndRegister() {
// 创建channel
final Channel channel = channelFactory().newChannel();
try {
// 初始化channel
init(channel);
} catch (Throwable t) {
channel.unsafe().closeForcibly();
return channel.newFailedFuture(t);
}
// 注册channel
ChannelFuture regFuture = group().register(channel);
if (regFuture.cause() != null) {
if (channel.isRegistered()) {
channel.close();
} else {
channel.unsafe().closeForcibly();
}
}
return regFuture;
}
//Bootstrap channel初始化部分
void init(Channel channel) throws Exception {
// 获取通道
ChannelPipeline p = channel.pipeline();
// 为通道添加handler,这里的handler就是我们添加的ChannelInitializer类
p.addLast(handler());
// 下面的一些配置就不是很重要的了
final Map<ChannelOption<?>, Object> options = options();
synchronized (options) {
for (Entry<ChannelOption<?>, Object> e: options.entrySet()) {
try {
if (!channel.config().setOption((ChannelOption<Object>) e.getKey(), e.getValue())) {
logger.warn("Unknown channel option: " + e);
}
} catch (Throwable t) {
logger.warn("Failed to set a channel option: " + channel, t);
}
}
}
final Map<AttributeKey<?>, Object> attrs = attrs();
synchronized (attrs) {
for (Entry<AttributeKey<?>, Object> e: attrs.entrySet()) {
channel.attr((AttributeKey<Object>) e.getKey()).set(e.getValue());
}
}
}
// MultithreadEventLoopGroup类
// group().register(channel)对应的注册
@Override
public ChannelFuture register(Channel channel) {
return next().register(channel);
}
// SingleThreadEventLoop 类
@Override
public ChannelFuture register(Channel channel) {
return register(channel, new DefaultChannelPromise(channel, this));
}
// AbstractChannel 类
@Override
public final void register(EventLoop eventLoop, final ChannelPromise promise) {
if (eventLoop == null) {
throw new NullPointerException("eventLoop");
}
if (isRegistered()) {
promise.setFailure(new IllegalStateException("registered to an event loop already"));
return;
}
if (!isCompatible(eventLoop)) {
promise.setFailure(
new IllegalStateException("incompatible event loop type: " + eventLoop.getClass().getName()));
return;
}
AbstractChannel.this.eventLoop = eventLoop;
if (eventLoop.inEventLoop()) {
register0(promise);
} else {
try {
eventLoop.execute(new Runnable() {
@Override
public void run() {
register0(promise);
}
});
} catch (Throwable t) {
logger.warn(
"Force-closing a channel whose registration task was not accepted by an event loop: {}",
AbstractChannel.this, t);
closeForcibly();
closeFuture.setClosed();
promise.setFailure(t);
}
}
}
// 再看register0()吧
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 (!ensureOpen(promise)) {
return;
}
// 真正执行注册
doRegister();
registered = true;
promise.setSuccess();
pipeline.fireChannelRegistered();
if (isActive()) {
pipeline.fireChannelActive();
}
} catch (Throwable t) {
// Close the channel directly to avoid FD leak.
closeForcibly();
closeFuture.setClosed();
if (!promise.tryFailure(t)) {
logger.warn(
"Tried to fail the registration promise, but it is complete already. " +
"Swallowing the cause of the registration failure:", t);
}
}
}
@Override
protected void doRegister() throws Exception {
boolean selected = false;
for (;;) {
try {
// 这里的javaChannel()是:java.nio.channels.SocketChannel,很明显这里的channel就是jdk中的channel
selectionKey = javaChannel().register(eventLoop().selector, 0, this);
return;
} catch (CancelledKeyException e) {
if (!selected) {
// Force the Selector to select now as the "canceled" SelectionKey may still be
// cached and not removed because no Select.select(..) operation was called yet.
eventLoop().selectNow();
selected = true;
} else {
// We forced a select operation on the selector before but the SelectionKey is still cached
// for whatever reason. JDK bug ?
throw e;
}
}
}
}
ok,到了channel的初始化和注册完成了。继续看注册完了之后
private ChannelFuture doConnect(final SocketAddress remoteAddress, final SocketAddress localAddress) {
final ChannelFuture regFuture = initAndRegister();
final Channel channel = regFuture.channel();
if (regFuture.cause() != null) {
return regFuture;
}
final ChannelPromise promise = channel.newPromise();
if (regFuture.isDone()) {
doConnect0(regFuture, channel, remoteAddress, localAddress, promise);
} else {
// 添加监听器
regFuture.addListener(new ChannelFutureListener() {
// 将会在调用sync之后调用此方法
@Override
public void operationComplete(ChannelFuture future) throws Exception {
doConnect0(regFuture, channel, remoteAddress, localAddress, promise);
}
});
}
return promise;
}
// 调用sync()之后
private static void doConnect0(
final ChannelFuture regFuture, final Channel channel,
final SocketAddress remoteAddress, final SocketAddress localAddress, final ChannelPromise promise) {
channel.eventLoop().execute(new Runnable() {
@Override
public void run() {
if (regFuture.isSuccess()) {
if (localAddress == null) {
//channel: java.nio.channels.SocketChannel
// 真正连接了
channel.connect(remoteAddress, promise);
} else {
channel.connect(remoteAddress, localAddress, promise);
}
promise.addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
} else {
promise.setFailure(regFuture.cause());
}
}
});
}
三、总结
总的来说,client的源码和server端的开启还是有点类似的,如果服务端的源码能大致了解,那么client比较简单的了~~~
