代码:
public final class Server {
public static void main(String[] args) throws Exception {
EventLoopGroup bossGroup = new NioEventLoopGroup(1);// 对应的开线程去accept
EventLoopGroup workerGroup = new NioEventLoopGroup();// 服务端处理客户端的数据
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup) // 配置进去
.channel(NioServerSocketChannel.class) // 设置服务端的socketChannel就是socket
.childOption(ChannelOption.TCP_NODELAY, true) // 给客户端的连接设置基本的tcp属性
.childAttr(AttributeKey.newInstance("childAttr"), "childAttrValue") // 每次创建客户端连接绑定基本的属性
.handler(new ServerHandler()) // 打印状态信息
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) {// 数据流读写的处理逻辑
ch.pipeline().addLast(new AuthHandler());
//..
}
});
ChannelFuture f = b.bind(8888).sync();
f.channel().closeFuture().sync();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
------------------------------------------3-1-------------------------------------------
服务端启动的四个过程:
1.创建服务端channel
2.初始化服务端channel
3.注册selector
4.端口绑定
---------------------------------------------------------------------------------
1.创建服务端channel:
第一步:入口
ChannelFuture f = b.bind(8888).sync();
第二步:一直跟进去
第三步:
final ChannelFuture initAndRegister() {
Channel channel = null;
try {
channel = channelFactory.newChannel();
init(channel);
} catch (Throwable t) {
if (channel != null) {
channel.unsafe().closeForcibly();
}
return new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE).setFailure(t);
}
ChannelFuture regFuture = config().group().register(channel);
if (regFuture.cause() != null) {
if (channel.isRegistered()) {
channel.close();
} else {
channel.unsafe().closeForcibly();
}
}
return regFuture;
}
第四步:进去newChannel
@Override
public T newChannel() {
try {
return clazz.newInstance();// 通过反射new的channel
} catch (Throwable t) {
throw new ChannelException("Unable to create Channel from class " + clazz, t);
}
}
第五步:我们看下clazz是什么就是一个channel,首先看下channelFactory是在哪里初始化的。
我们看下这个.channel到底做了哪些事情
public B channel(Class<? extends C> channelClass) {
if (channelClass == null) {
throw new NullPointerException("channelClass");
}
return channelFactory(new ReflectiveChannelFactory<C>(channelClass));
}
第六步:我们只需要关注,通过NioServerSocketChannel这个了构造了一个反射的工厂。
new ReflectiveChannelFactory<C>(channelClass)
所以综合就是传入这个类,通过反射的方式调用这个类的构造函数。
过程:
概括为:
第一个过程:在NioServerSocketChannel的构造函数中我们创建了一个jdk原生的ServerSocketChannel
public NioServerSocketChannel() {
this(newSocket(DEFAULT_SELECTOR_PROVIDER));
}
private static ServerSocketChannel newSocket(SelectorProvider provider) {
try {
/**
* Use the {@link SelectorProvider} to open {@link SocketChannel} and so remove condition in
* {@link SelectorProvider#provider()} which is called by each ServerSocketChannel.open() otherwise.
*
* See <a href="https://github.com/netty/netty/issues/2308">#2308</a>.
*/
return provider.openServerSocketChannel();
} catch (IOException e) {
throw new ChannelException(
"Failed to open a server socket.", e);
}
}
第二个过程:tcp参数 ,通过NioServerSocketChannelConfig配置服务端Channel的构造函数
public NioServerSocketChannel(ServerSocketChannel channel) {
super(null, channel, SelectionKey.OP_ACCEPT);
config = new NioServerSocketChannelConfig(this, javaChannel().socket());
}
第三个过程,调用父类的构造函数
进去:NIO编程,主要是配置NIO的SocketChannel是非阻塞的
protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) {
super(parent);
this.ch = ch;
this.readInterestOp = readInterestOp;
try {
ch.configureBlocking(false);// 配置 Java NIO SocketChannel 为非阻塞的
} catch (IOException e) {
try {
ch.close();
} catch (IOException e2) {
if (logger.isWarnEnabled()) {
logger.warn(
"Failed to close a partially initialized socket.", e2);
}
}
throw new ChannelException("Failed to enter non-blocking mode.", e);
}
}
第四个过程:第、调用AbstractChannel这个抽象类的构造函数设置Channel的id(每个Channel都有一个id,唯一标识),unsafe(tcp相关底层操作),pipeline(逻辑链)等,而不管是服务的Channel还是客户端的Channel都继承自这个抽象类,他们也都会有上述相应的属性。我们看下AbstractChannel的构造函数
不管是服务端还是客户端的Channel都集成自这个抽象的Channel,其中传入了id unsafe这个是tcp读写操作的一个类 逻辑链。
protected AbstractChannel(Channel parent) {
this.parent = parent;
id = newId();//创建Channel唯一标识
unsafe = newUnsafe();//netty封装的TCP 相关操作类
pipeline = newChannelPipeline();//逻辑链
}
总结:服务端的channel是反射创建的。
------------------------------------------3-2-------------------------------------------
第一步:配置用户自定义的ChannelOptions和ChannelAttrs,这个用的不是很对
第二步:配置用户自定义的ChildOptions和ChildAttrs,这个每次创建新的来连接都会自定义这两个属性。
第三步:配置服务端的pipeLine。通过header设置进去的。
第四步:给accept的新连接分配一个nio的线程。
总结:
设置ChannelOptions、ChannelAttrs ,配置服务端Channel的相关属性;
设置ChildOptions、ChildAttrs,配置每个新连接的Channel的相关属性;
Config handler,配置服务端pipeline;
add ServerBootstrapAcceptor,添加连接器,对accpet接受到的新连接进行处理,添加一个nio线程;
第一步:
第二步:我们分析的代码
@Override
}
final Map<ChannelOption<?>, Object> options = options0();
synchronized (options) {
channel.config().setOptions(options);// 设置NioServerSocketChannel相应的TCP参数,其实这一步就是把options设置到channel的config中
}
final Map<AttributeKey<?>, Object> attrs = attrs0();// 绑定用户自定义的属性
synchronized (attrs) {
for (Entry<AttributeKey<?>, Object> e: attrs.entrySet()) {
@SuppressWarnings("unchecked")
AttributeKey<Object> key = (AttributeKey<Object>) e.getKey();
channel.attr(key).set(e.getValue());
}
}
ChannelPipeline p = channel.pipeline();
final EventLoopGroup currentChildGroup = childGroup;
final ChannelHandler currentChildHandler = childHandler;
final Entry<ChannelOption<?>, Object>[] currentChildOptions;
final Entry<AttributeKey<?>, Object>[] currentChildAttrs;
synchronized (childOptions) {// 1
currentChildOptions = childOptions.entrySet().toArray(newOptionArray(childOptions.size()));
}
synchronized (childAttrs) {// 2
currentChildAttrs = childAttrs.entrySet().toArray(newAttrArray(childAttrs.size()));
}
p.addLast(new ChannelInitializer<Channel>() {// 对服务端Channel的handler进行配置
@Override
public void initChannel(Channel ch) throws Exception {
final ChannelPipeline pipeline = ch.pipeline();
ChannelHandler handler = config.handler(); // 自定义的handler添加进去
if (handler != null) {
pipeline.addLast(handler);
}
ch.eventLoop().execute(new Runnable() {
@Override
public void run() {
pipeline.addLast(new ServerBootstrapAcceptor(
currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs));
}
});
}
});
}
第三步:
服务端启动会默认添加特殊的处理器。
ch.eventLoop().execute(new Runnable() {
@Override
public void run() {//在这里会把我们自定义的ChildGroup、ChildHandler、ChildOptions、ChildAttrs相关配置传入到ServerBootstrapAcceptor构造函数中,并绑定到新的连接上
pipeline.addLast(new ServerBootstrapAcceptor(
currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs));
}
});
currentChildHandler:我们自己定义的。
总结:保存属性,创建连接接入器,每次accept新的连接都会对连接进行配置。
------------------------------------------3-3-------------------------------------------
一个服务端的Channel创建完毕后,下一步就是要把它注册到一个事件轮询器Selector上,在initAndRegister()中我们把上面初始化的Channel进行注册。
找到这个:
final ChannelFuture initAndRegister() {
Channel channel = null;
try {
channel = channelFactory.newChannel();
init(channel);
} catch (Throwable t) {
if (channel != null) {
channel.unsafe().closeForcibly();
}
return new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE).setFailure(t);
}
ChannelFuture regFuture = config().group().register(channel);// 这个方法
if (regFuture.cause() != null) {
if (channel.isRegistered()) {
channel.close();
} else {
channel.unsafe().closeForcibly();
}
}
return regFuture;
}
@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();
safeSetFailure(promise, t);
}
}
}
逻辑概括:
点进去register0我们主要的关注点在doRegister方法。
@Override
protected void doRegister() throws Exception {
boolean selected = false;
for (;;) {
try {
selectionKey = javaChannel().register(eventLoop().selector, 0, this);
return;
} catch (CancelledKeyException e) {
if (!selected) {
eventLoop().selectNow();
selected = true;
} else {
throw e;
}
}
}
}
进去register0,进入doRegister,this就是服务端得的channel,我们绑定到selector上面去。
回到用户代码:
进入这里可以看到事件的回调:
@Override
public void channelActive(ChannelHandlerContext ctx) {
System.out.println("channelActive");
}
@Override
public void channelRegistered(ChannelHandlerContext ctx) {
System.out.println("channelRegistered");
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) {
System.out.println("handlerAdded");
}
根据流程主要触发后两个事件。
-------------------------------------------3-4-----------------------------------------
端口的绑定:
我们进入doBind方法进行分析:
private ChannelFuture doBind(final SocketAddress localAddress) {
final ChannelFuture regFuture = initAndRegister();
final Channel channel = regFuture.channel();
if (regFuture.cause() != null) {
return regFuture;
}
if (regFuture.isDone()) {
ChannelPromise promise = channel.newPromise();
doBind0(regFuture, channel, localAddress, promise);
return promise;
} else {
final PendingRegistrationPromise promise = new PendingRegistrationPromise(channel);
regFuture.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
Throwable cause = future.cause();
if (cause != null) {
promise.setFailure(cause);
} else {
promise.registered();
doBind0(regFuture, channel, localAddress, promise);
}
}
});
return promise;
}
}
我们看下doBind0。
我们进入到AbstrateChannel看下:
@Override
public final void bind(final SocketAddress localAddress, final ChannelPromise promise) {
assertEventLoop();
if (!promise.setUncancellable() || !ensureOpen(promise)) {
return;
}
if (Boolean.TRUE.equals(config().getOption(ChannelOption.SO_BROADCAST)) &&
localAddress instanceof InetSocketAddress &&
!((InetSocketAddress) localAddress).getAddress().isAnyLocalAddress() &&
!PlatformDependent.isWindows() && !PlatformDependent.isRoot()) {
logger.warn(
"A non-root user can't receive a broadcast packet if the socket " +
"is not bound to a wildcard address; binding to a non-wildcard " +
"address (" + localAddress + ") anyway as requested.");
}
boolean wasActive = isActive();判断绑定是否完成
try {
doBind(localAddress);//底层jdk绑定端口
} catch (Throwable t) {
safeSetFailure(promise, t);
closeIfClosed();
return;
}
if (!wasActive && isActive()) {
invokeLater(new Runnable() {
@Override
public void run() {
pipeline.fireChannelActive();
}
});
}
safeSetSuccess(promise);
}
进入doBind方法:
@Override
protected void doBind(SocketAddress localAddress) throws Exception {
if (PlatformDependent.javaVersion() >= 7) {
javaChannel().bind(localAddress, config.getBacklog());// JDk底层的channel
} else {
javaChannel().socket().bind(localAddress, config.getBacklog());
}
}
进入:在 pipeline.fireChannelActive()中会触发pipeline中的channelActive()方法
调用readIfIsAutoRead函数一直跟:
上面那些参数是怎么来的?
总结:调用jdk的api作为实际的绑定,触发事件,调用redisIfIsAutoRead,层层调用到doBeginRead方法。
在doBeginRead()方法,netty会把accept事件注册到Selector上。
-------------------------------------------3-5-----------------------------------------
总结:
总结:调用newChannel()创建服务端的channel,过程实际上就是调用JDK底层的API,创建一个JDK的内存,netty将其包装为一个,自己的服务端的channel,同时会创建一些基本的组件,比如pipline,同时调用init方法,初始化服务端的channel,为服务端channel添加一个连接处理器。随后调用register方法,注册selector,绑定到JDK底层的channel,调用JDK底层的api实现。
-------------------------------------------------------------3-6-------------------------------------------------------------
最后的总结看下这篇文章:https://www.cnblogs.com/dafanjoy/p/9810189.html