netty 多线程事件执行器组： http://donald-draper.iteye.com/blog/2391270
netty 多线程事件循环组： http://donald-draper.iteye.com/blog/2391276
netty 抽象调度事件执行器： http://donald-draper.iteye.com/blog/2391379
netty 单线程事件执行器初始化： http://donald-draper.iteye.com/blog/2391895
netty 单线程事件执行器执行任务与graceful方式关闭： http://donald-draper.iteye.com/blog/2392051
netty 单线程事件循环： http://donald-draper.iteye.com/blog/2392067
netty nio事件循环初始化： http://donald-draper.iteye.com/blog/2392161
netty nio事件循环后续： http://donald-draper.iteye.com/blog/2392264
netty nio事件循环组： http://donald-draper.iteye.com/blog/2392300
前面我们来看netty的事件循环，从今天起，我们来看一下BootStap和ServerBootStrap：
在netty的相关测试实例中服务端有如下代码：
EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
//ServerBootstrap，用于配置服务端，一般为ServerSocket通道
ServerBootstrap serverBoot = new ServerBootstrap();
serverBoot.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
//添加通道处理器到通道关联的管道，准确的中文翻译为管道线， 此管道线与Mina中过滤链十分相似,
//ChannelInitializer用于配置通道的管道线，ChannelPipeline
ChannelPipeline pipeline = ch.pipeline();
if (sslCtx != null) {
pipeline.addLast(sslCtx.newHandler(ch.alloc()));
}
pipeline.addLast(new LoggingHandler(LogLevel.INFO));
pipeline.addLast(new EchoServerHandler());
}
})
.option(ChannelOption.SO_BACKLOG, 128)//socket监听器连接队列大小、
.childOption(ChannelOption.SO_KEEPALIVE, true); //保活，此配置针对ServerSocket通道接收连接产生的Socket通道
InetSocketAddress inetSocketAddress = new InetSocketAddress(ip,port);
// 绑定地址，开始监听
ChannelFuture f = serverBoot.bind(inetSocketAddress).sync();
log.info("=========Server is start=========");
//等待，直到ServerSocket关闭
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
而客户端的为：
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
//Bootstrap，用于配置客户端，一般为Socket通道
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(workerGroup)
.channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
//添加安全套接字处理器和通道处理器到
ChannelPipeline pipeline = ch.pipeline();
if (sslCtx != null) {
pipeline.addLast(sslCtx.newHandler(ch.alloc(), ip, port));
}
pipeline.addLast(new LoggingHandler(LogLevel.INFO));
pipeline.addLast(new EchoClientHandler());
}
});
InetSocketAddress inetSocketAddress = new InetSocketAddress(ip,port);
//连接socket地址
ChannelFuture f = bootstrap.connect(inetSocketAddress).sync();
log.info("=========Client is start=========");
//等待，直到连接关闭
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
}
上面有两个类型我们需要关注，是下面两句：
ServerBootstrap serverBoot = new ServerBootstrap(); Bootstrap bootstrap = new Bootstrap();
从上面来看服务端引导配置ServerBootstrap用于配置服务端的Nio事件循环组，通道，通道处理器，及通道相关配置，客户端引导配置Bootstap用于配置客户端的Nio事件循环组，通道，通道处理器，及通道相关配置。
我们来看一下两种引导配置的定义：
public class ServerBootstrap extends AbstractBootstrap<ServerBootstrap, ServerChannel>
public class Bootstrap extends AbstractBootstrap<Bootstrap, Channel> {
两种引导配置都继承与AbstractBootstrap，只是类型参数不同，服务端通道类型参数为ServerChannel，
客户端为Channel。
我们先来看一下AbstractBootstrap：
package io.netty.bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPromise;
import io.netty.channel.DefaultChannelPromise;
import io.netty.channel.EventLoop;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.ReflectiveChannelFactory;
import io.netty.util.internal.SocketUtils;
import io.netty.util.AttributeKey;
import io.netty.util.concurrent.EventExecutor;
import io.netty.util.concurrent.GlobalEventExecutor;
import io.netty.util.internal.StringUtil;
import io.netty.util.internal.logging.InternalLogger;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* {@link AbstractBootstrap} is a helper class that makes it easy to bootstrap a {@link Channel}. It support
* method-chaining to provide an easy way to configure the {@link AbstractBootstrap}.
*抽象引导程序AbstractBootstrap使启动一个通道更容易的工具类。支持链式方法编程，提供配置抽象引导程序的便捷方式。
* When not used in a {@link ServerBootstrap} context, the {@link #bind()} methods are useful for connectionless
* transports such as datagram (UDP).
当不在Server引导程序上下文下使用时，绑定方法可以用于无连接的传输，比如报文传输
*/
public abstract class AbstractBootstrap<B extends AbstractBootstrap<B, C>, C extends Channel> implements Cloneable {
volatile EventLoopGroup group;//事件循环组
@SuppressWarnings("deprecation")
private volatile ChannelFactory<? extends C> channelFactory;//通道工厂，已丢器
private volatile SocketAddress localAddress;//本地socket地址
//通道配置项
private final Map<ChannelOption<?>, Object> options = new LinkedHashMap<ChannelOption<?>, Object>();
//通道属性
private final Map<AttributeKey<?>, Object> attrs = new LinkedHashMap<AttributeKey<?>, Object>();
private volatile ChannelHandler handler;//通道处理器
AbstractBootstrap() {
// Disallow extending from a different package.
}
AbstractBootstrap(AbstractBootstrap<B, C> bootstrap) {
group = bootstrap.group;
channelFactory = bootstrap.channelFactory;
handler = bootstrap.handler;
localAddress = bootstrap.localAddress;
synchronized (bootstrap.options) {
options.putAll(bootstrap.options);
}
synchronized (bootstrap.attrs) {
attrs.putAll(bootstrap.attrs);
}
}
}
从上面来看抽象引导程序AbstractBootstrap，内部关联的一个事件循环组EventLoopGroup，
一个通道处理器ChannelHandler，一个通道配置集和一个本地Socket地址及一个通道属性集。
下面来看其他方法：
/**
* The {@link EventLoopGroup} which is used to handle all the events for the to-be-created
* {@link Channel}
配置事件循环组，处理所有创建的事件
*/
@SuppressWarnings("unchecked")
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;
}
/**
* The {@link Class} which is used to create {@link Channel} instances from.
* You either use this or {@link #channelFactory(io.netty.channel.ChannelFactory)} if your
* {@link Channel} implementation has no no-args constructor.
通道类channelClass，用于创建通道实例，如果你的通道实现为无参构造可以使用此方法或
#channelFactory
*/
public B channel(Class<? extends C> channelClass) {
if (channelClass == null) {
throw new NullPointerException("channelClass");
}
return channelFactory(new ReflectiveChannelFactory<C>(channelClass));
}
/**
* {@link io.netty.channel.ChannelFactory} which is used to create {@link Channel} instances from
* when calling {@link #bind()}. This method is usually only used if {@link #channel(Class)}
* is not working for you because of some more complex needs. If your {@link Channel} implementation
* has a no-args constructor, its highly recommend to just use {@link #channel(Class)} for
* simplify your code.
当调用绑定方法时，通道工厂由于创建通道实例。
*/
@SuppressWarnings({ "unchecked", "deprecation" })
public B channelFactory(io.netty.channel.ChannelFactory<? extends C> channelFactory) {
return channelFactory((ChannelFactory<C>) channelFactory);
}
**
* @deprecated Use {@link #channelFactory(io.netty.channel.ChannelFactory)} instead.
*/
@Deprecated
@SuppressWarnings("unchecked")
public B channelFactory(ChannelFactory<? extends C> channelFactory) {
if (channelFactory == null) {
throw new NullPointerException("channelFactory");
}
if (this.channelFactory != null) {
throw new IllegalStateException("channelFactory set already");
}
this.channelFactory = channelFactory;
return (B) this;
}
回到配置通道方法的这一句：
return channelFactory(new ReflectiveChannelFactory<C>(channelClass));
我们来看一下反射通道工厂：
package io.netty.channel;
import io.netty.util.internal.StringUtil;
/**
* A {@link ChannelFactory} that instantiates a new {@link Channel} by invoking its default constructor reflectively.
*/
public class ReflectiveChannelFactory<T extends Channel> implements ChannelFactory<T> {
private final Class<? extends T> clazz;
public ReflectiveChannelFactory(Class<? extends T> clazz) {
if (clazz == null) {
throw new NullPointerException("clazz");
}
this.clazz = clazz;
}
//创建通道实例
@Override
public T newChannel() {
try {
return clazz.newInstance();
} catch (Throwable t) {
throw new ChannelException("Unable to create Channel from class " + clazz, t);
}
}
@Override
public String toString() {
return StringUtil.simpleClassName(clazz) + ".class";
}
}
再来看配置本地地址：
/**
* The {@link SocketAddress} which is used to bind the local "end" to.
*/
@SuppressWarnings("unchecked")
public B localAddress(SocketAddress localAddress) {
this.localAddress = localAddress;
return (B) this;
}
/**
* @see #localAddress(SocketAddress)
*/
public B localAddress(int inetPort) {
return localAddress(new InetSocketAddress(inetPort));
}
/**
* @see #localAddress(SocketAddress)
*/
public B localAddress(String inetHost, int inetPort) {
return localAddress(SocketUtils.socketAddress(inetHost, inetPort));
}
/**
* @see #localAddress(SocketAddress)
*/
public B localAddress(InetAddress inetHost, int inetPort) {
return localAddress(new InetSocketAddress(inetHost, inetPort));
}
再来看配置通道选项
/
**
* Allow to specify a {@link ChannelOption} which is used for the {@link Channel} instances once they got
* created. Use a value of {@code null} to remove a previous set {@link ChannelOption}.
*/
@SuppressWarnings("unchecked")
public <T> B option(ChannelOption<T> option, T value) {
if (option == null) {
throw new NullPointerException("option");
}
if (value == null) {
//置为空，则移除通道配置选项
synchronized (options) {
options.remove(option);
}
} else {
//否则添加通道配置选择到配置选项集
synchronized (options) {
options.put(option, value);
}
}
return (B) this;
}
ChannelOption定义见附篇。
//配置通道属性，与配置通道选项思路相同
/**
* Allow to specify an initial attribute of the newly created {@link Channel}. If the {@code value} is
* {@code null}, the attribute of the specified {@code key} is removed.
*/
@SuppressWarnings("unchecked")
public <T> B attr(AttributeKey<T> key, T value) {
if (key == null) {
throw new NullPointerException("key");
}
if (value == null) {
synchronized (attrs) {
attrs.remove(key);
}
} else {
synchronized (attrs) {
attrs.put(key, value);
}
}
return (B) this;
}
AttributeKey定义见附篇。
/**
* Validate all the parameters. Sub-classes may override this, but should
* call the super method in that case.
验证参数，子类可以重写此方法
*/
@SuppressWarnings("unchecked")
public B validate() {
if (group == null) {
throw new IllegalStateException("group not set");
}
if (channelFactory == null) {
throw new IllegalStateException("channel or channelFactory not set");
}
return (B) this;
}
/**
* Returns a deep clone of this bootstrap which has the identical configuration. This method is useful when making
* multiple {@link Channel}s with similar settings. Please note that this method does not clone the
* {@link EventLoopGroup} deeply but shallowly, making the group a shared resource.
克隆引导配置
*/
@Override
@SuppressWarnings("CloneDoesntDeclareCloneNotSupportedException")
public abstract B clone();
/**
* Create a new {@link Channel} and register it with an {@link EventLoop}.
创建一个通道，注册到事件循环
*/
public ChannelFuture register() {
validate();
return initAndRegister();
}
//初始化通道，注册通道到事件循环
final ChannelFuture initAndRegister() {
Channel channel = null;
try {
//创建通道实例
channel = channelFactory.newChannel();
init(channel);//初始化通道
} catch (Throwable t) {
if (channel != null) {
// channel can be null if newChannel crashed (eg SocketException("too many open files"))
channel.unsafe().closeForcibly();
}
// as the Channel is not registered yet we need to force the usage of the GlobalEventExecutor
return new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE).setFailure(t);
}
//委托给事件循环组
ChannelFuture regFuture = config().group().register(channel);
if (regFuture.cause() != null) {
if (channel.isRegistered()) {
channel.close();
} else {
channel.unsafe().closeForcibly();
}
}
// If we are here and the promise is not failed, it's one of the following cases:
// 1) If we attempted registration from the event loop, the registration has been completed at this point.
// i.e. It's safe to attempt bind() or connect() now because the channel has been registered.
// 2) If we attempted registration from the other thread, the registration request has been successfully
// added to the event loop's task queue for later execution.
// i.e. It's safe to attempt bind() or connect() now:
// because bind() or connect() will be executed *after* the scheduled registration task is executed
// because register(), bind(), and connect() are all bound to the same thread.
return regFuture;
}
//初始化通道 abstract void init(Channel channel) throws Exception;
/**
* Returns the {@link AbstractBootstrapConfig} object that can be used to obtain the current config
* of the bootstrap.
获取启动项当前配置
*/
public abstract AbstractBootstrapConfig<B, C> config();
从上面可以看出，注册通道到事件循环组，首先由通道工厂创建通道实例，然后初始化通道，初始化工作待子类实现；然后将实际注册工作委托给事件循环组。
再来看地址绑定方法：
/**
* Create a new {@link Channel} and bind it.
*/
public ChannelFuture bind() {
validate();
SocketAddress localAddress = this.localAddress;
if (localAddress == null) {
throw new IllegalStateException("localAddress not set");
}
return doBind(localAddress);
}
/**
* Create a new {@link Channel} and bind it.
*/
public ChannelFuture bind(int inetPort) {
return bind(new InetSocketAddress(inetPort));
}
/**
* Create a new {@link Channel} and bind it.
*/
public ChannelFuture bind(String inetHost, int inetPort) {
return bind(SocketUtils.socketAddress(inetHost, inetPort));
}
//SocketUtils
/**
* Provides socket operations with privileges enabled. This is necessary for applications that use the
* {@link SecurityManager} to restrict {@link SocketPermission} to their application. By asserting that these
* operations are privileged, the operations can proceed even if some code in the calling chain lacks the appropriate
* {@link SocketPermission}.
socket操作访问控制权限Utils
*/
public final class SocketUtils {
...
private SocketUtils() {
}
//在当前访问控制权限下，根据主机名和端口号创建Socket地址
public static InetSocketAddress socketAddress(final String hostname, final int port) {
return AccessController.doPrivileged(new PrivilegedAction<InetSocketAddress>() {
@Override
public InetSocketAddress run() {
return new InetSocketAddress(hostname, port);
}
});
}
...
}
/**
* Create a new {@link Channel} and bind it.
*/
public ChannelFuture bind(InetAddress inetHost, int inetPort) {
return bind(new InetSocketAddress(inetHost, inetPort));
}
/**
* Create a new {@link Channel} and bind it.
*/
public ChannelFuture bind(SocketAddress localAddress) {
validate();
if (localAddress == null) {
throw new NullPointerException("localAddress");
}
return doBind(localAddress);
}
从上面来看，绑定socket地址实际通过doBind方法
private ChannelFuture doBind(final SocketAddress localAddress) {
//首先注册通道到事件循环组
final ChannelFuture regFuture = initAndRegister();
final Channel channel = regFuture.channel();
//异常返回
if (regFuture.cause() != null) {
return regFuture;
}
if (regFuture.isDone()) {
// At this point we know that the registration was complete and successful.
ChannelPromise promise = channel.newPromise();
//通道注册到时间循环组，成功，委托给doBind0完成实际socket的地址绑定
doBind0(regFuture, channel, localAddress, promise);
return promise;
} else {
// Registration future is almost always fulfilled already, but just in case it's not.
//注册工作大部分情况下，已经完成，但有可能存在意外情况
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) {
// Registration on the EventLoop failed so fail the ChannelPromise directly to not cause an
// IllegalStateException once we try to access the EventLoop of the Channel.
promise.setFailure(cause);
} else {
// Registration was successful, so set the correct executor to use.
// See https://github.com/netty/netty/issues/2586
//注册成功，执行器可以使用
promise.registered();
doBind0(regFuture, channel, localAddress, promise);
}
}
});
return promise;
}
}
//PendingRegistrationPromise,通道注册任务异步任务结果
static final class PendingRegistrationPromise extends DefaultChannelPromise {
// Is set to the correct EventExecutor once the registration was successful. Otherwise it will
// stay null and so the GlobalEventExecutor.INSTANCE will be used for notifications.
private volatile boolean registered;
PendingRegistrationPromise(Channel channel) {
super(channel);
}
void registered() {
registered = true;
}
@Override
protected EventExecutor executor() {
if (registered) {
// If the registration was a success executor is set.
//注册成功，即通道注册到nio事件循环中，然后获取nio事件循环的事件执行器
// See https://github.com/netty/netty/issues/2586
return super.executor();
}
// The registration failed so we can only use the GlobalEventExecutor as last resort to notify.
return GlobalEventExecutor.INSTANCE;
}
}
再来看实际绑定工作
private static void doBind0(
final ChannelFuture regFuture, final Channel channel,
final SocketAddress localAddress, final ChannelPromise promise) {
// This method is invoked before channelRegistered() is triggered. Give user handlers a chance to set up
// the pipeline in its channelRegistered() implementation.
// 此方法在通道注册前触发调用。
channel.eventLoop().execute(new Runnable() {
@Override
public void run() {
if (regFuture.isSuccess()) {
//委托给通道
channel.bind(localAddress, promise).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
} else {
promise.setFailure(regFuture.cause());
}
}
});
}
从上面可以看出绑定socket地址，首先注册通道到事件循环组，待注册完成时，创建一个绑定任务线程完成地址绑定，
实际将地址绑定工作委托给通道，并将绑定任务线程交由通道关联的事件循环的事件执行器执行。
再来看其他方法，
/**
* the {@link ChannelHandler} to use for serving the requests.
配置通道处理器
*/
@SuppressWarnings("unchecked")
public B handler(ChannelHandler handler) {
if (handler == null) {
throw new NullPointerException("handler");
}
this.handler = handler;
return (B) this;
}
/**
* Returns the configured {@link EventLoopGroup} or {@code null} if non is configured yet.
*返回事件循环组
* @deprecated Use {@link #config()} instead.
*/
@Deprecated
public final EventLoopGroup group() {
return group;
}
//拷贝Map
static <K, V> Map<K, V> copiedMap(Map<K, V> map) {
final Map<K, V> copied;
synchronized (map) {
if (map.isEmpty()) {
return Collections.emptyMap();
}
copied = new LinkedHashMap<K, V>(map);
}
return Collections.unmodifiableMap(copied);
}
下面几个方法主要是获取通道属性，通道选型，通道处理器，通道工厂
final Map<ChannelOption<?>, Object> options0() {
return options;
}
final Map<AttributeKey<?>, Object> attrs0() {
return attrs;
}
final SocketAddress localAddress() {
return localAddress;
}
@SuppressWarnings("deprecation")
final ChannelFactory<? extends C> channelFactory() {
return channelFactory;
}
final ChannelHandler handler() {
return handler;
}
final Map<ChannelOption<?>, Object> options() {
return copiedMap(options);
}
final Map<AttributeKey<?>, Object> attrs() {
return copiedMap(attrs);
}
//设置通道选项
static void setChannelOptions(
Channel channel, Map<ChannelOption<?>, Object> options, InternalLogger logger) {
for (Map.Entry<ChannelOption<?>, Object> e: options.entrySet()) {
setChannelOption(channel, e.getKey(), e.getValue(), logger);
}
}
static void setChannelOptions(
Channel channel, Map.Entry<ChannelOption<?>, Object>[] options, InternalLogger logger) {
for (Map.Entry<ChannelOption<?>, Object> e: options) {
setChannelOption(channel, e.getKey(), e.getValue(), logger);
}
}
//配置通道选项
@SuppressWarnings("unchecked")
private static void setChannelOption(
Channel channel, ChannelOption<?> option, Object value, InternalLogger logger) {
try {
if (!channel.config().setOption((ChannelOption<Object>) option, value)) {
logger.warn("Unknown channel option '{}' for channel '{}'", option, channel);
}
} catch (Throwable t) {
logger.warn(
"Failed to set channel option '{}' with value '{}' for channel '{}'", option, value, channel, t);
}
}
总结：
抽象引导程序AbstractBootstrap，内部关联的一个事件循环组EventLoopGroup，一个通道处理器ChannelHandler，一个通道选项集和一个本地Socket地址及一个通道属性集。内部的方法主要配置事件循环组，通道处理，通道选项集，socket地址，及通道属性，通道注册，地址绑定。注册通道到事件循环组，首先由通道工厂创建通道实例，然后初始化通道，初始化工作待子类实现；然后将实际注册工作委托给事件循环组。绑定定socket地址，首先注册通道到事件循环组，待注册完成时，创建一个绑定任务线程完成地址绑定，实际将地址绑定工作委托给通道，并将绑定任务线程交由通道关联的事件循环的事件执行器执行。
附：
package io.netty.channel;
import io.netty.buffer.ByteBufAllocator;
import io.netty.util.AbstractConstant;
import io.netty.util.ConstantPool;
import java.net.InetAddress;
import java.net.NetworkInterface;
/**
* A {@link ChannelOption} allows to configure a {@link ChannelConfig} in a type-safe
* way. Which {@link ChannelOption} is supported depends on the actual implementation
* of {@link ChannelConfig} and may depend on the nature of the transport it belongs
* to.
*通道配置项运行以类型安全的方式配置通道选项，具体支持何种通道选项，依赖于具体的通道配置实现
或所属的传输类型transport
* @param <T> the type of the value which is valid for the {@link ChannelOption}
*/
public class ChannelOption<T> extends AbstractConstant<ChannelOption<T>> {
//常量池，存放配置选项常量
private static final ConstantPool<ChannelOption<Object>> pool = new ConstantPool<ChannelOption<Object>>() {
@Override
protected ChannelOption<Object> newConstant(int id, String name) {
return new ChannelOption<Object>(id, name);
}
};
/**
* Returns the {@link ChannelOption} of the specified name.
获取name对象的通道选项值
*/
@SuppressWarnings("unchecked")
public static <T> ChannelOption<T> valueOf(String name) {
return (ChannelOption<T>) pool.valueOf(name);
}
/**
* Shortcut of {@link #valueOf(String) valueOf(firstNameComponent.getName() + "#" + secondNameComponent)}.
获取firstNameComponent.getName() + "#" + secondNameComponent的属性值
*/
@SuppressWarnings("unchecked")
public static <T> ChannelOption<T> valueOf(Class<?> firstNameComponent, String secondNameComponent) {
return (ChannelOption<T>) pool.valueOf(firstNameComponent, secondNameComponent);
}
/**
* Returns {@code true} if a {@link ChannelOption} exists for the given {@code name}.
判断是否存在name对应的通道选项
*/
public static boolean exists(String name) {
return pool.exists(name);
}
/**
* Creates a new {@link ChannelOption} for the given {@code name} or fail with an
* {@link IllegalArgumentException} if a {@link ChannelOption} for the given {@code name} exists.
根据名字创建通道配置选项
*/
@SuppressWarnings("unchecked")
public static <T> ChannelOption<T> newInstance(String name) {
return (ChannelOption<T>) pool.newInstance(name);
}
//字节buf分配器
public static final ChannelOption<ByteBufAllocator> ALLOCATOR = valueOf("ALLOCATOR");
//接受buf分配器
public static final ChannelOption<RecvByteBufAllocator> RCVBUF_ALLOCATOR = valueOf("RCVBUF_ALLOCATOR");
//消息大小估算器
public static final ChannelOption<MessageSizeEstimator> MESSAGE_SIZE_ESTIMATOR = valueOf("MESSAGE_SIZE_ESTIMATOR");
//连接超时时间
public static final ChannelOption<Integer> CONNECT_TIMEOUT_MILLIS = valueOf("CONNECT_TIMEOUT_MILLIS");
/**
* @deprecated Use {@link MaxMessagesRecvByteBufAllocator}
每次读取，允许读取的最大消息
*/
@Deprecated
public static final ChannelOption<Integer> MAX_MESSAGES_PER_READ = valueOf("MAX_MESSAGES_PER_READ");
//每次写的自旋次数
public static final ChannelOption<Integer> WRITE_SPIN_COUNT = valueOf("WRITE_SPIN_COUNT");
/**
* @deprecated Use {@link #WRITE_BUFFER_WATER_MARK}
*/
@Deprecated
public static final ChannelOption<Integer> WRITE_BUFFER_HIGH_WATER_MARK = valueOf("WRITE_BUFFER_HIGH_WATER_MARK");
/**
* @deprecated Use {@link #WRITE_BUFFER_WATER_MARK}
*/
@Deprecated
public static final ChannelOption<Integer> WRITE_BUFFER_LOW_WATER_MARK = valueOf("WRITE_BUFFER_LOW_WATER_MARK");
public static final ChannelOption<WriteBufferWaterMark> WRITE_BUFFER_WATER_MARK =
valueOf("WRITE_BUFFER_WATER_MARK");
public static final ChannelOption<Boolean> ALLOW_HALF_CLOSURE = valueOf("ALLOW_HALF_CLOSURE");
public static final ChannelOption<Boolean> AUTO_READ = valueOf("AUTO_READ");
/**
* @deprecated Auto close will be removed in a future release.
*
* If {@code true} then the {@link Channel} is closed automatically and immediately on write failure.
* The default value is {@code true}.
*/
@Deprecated
public static final ChannelOption<Boolean> AUTO_CLOSE = valueOf("AUTO_CLOSE");
//下面这些配置项就与socket的相关配置，我们在nio分类博客中有讲，下面这些用于socket通道
public static final ChannelOption<Boolean> SO_BROADCAST = valueOf("SO_BROADCAST");
public static final ChannelOption<Boolean> SO_KEEPALIVE = valueOf("SO_KEEPALIVE");
public static final ChannelOption<Integer> SO_SNDBUF = valueOf("SO_SNDBUF");
public static final ChannelOption<Integer> SO_RCVBUF = valueOf("SO_RCVBUF");
public static final ChannelOption<Boolean> SO_REUSEADDR = valueOf("SO_REUSEADDR");
public static final ChannelOption<Integer> SO_LINGER = valueOf("SO_LINGER");
public static final ChannelOption<Integer> SO_BACKLOG = valueOf("SO_BACKLOG");
public static final ChannelOption<Integer> SO_TIMEOUT = valueOf("SO_TIMEOUT");
//用于报文通道
public static final ChannelOption<Integer> IP_TOS = valueOf("IP_TOS");
public static final ChannelOption<InetAddress> IP_MULTICAST_ADDR = valueOf("IP_MULTICAST_ADDR");
public static final ChannelOption<NetworkInterface> IP_MULTICAST_IF = valueOf("IP_MULTICAST_IF");
public static final ChannelOption<Integer> IP_MULTICAST_TTL = valueOf("IP_MULTICAST_TTL");
public static final ChannelOption<Boolean> IP_MULTICAST_LOOP_DISABLED = valueOf("IP_MULTICAST_LOOP_DISABLED");
public static final ChannelOption<Boolean> TCP_NODELAY = valueOf("TCP_NODELAY");
@Deprecated
public static final ChannelOption<Boolean> DATAGRAM_CHANNEL_ACTIVE_ON_REGISTRATION =
valueOf("DATAGRAM_CHANNEL_ACTIVE_ON_REGISTRATION");
public static final ChannelOption<Boolean> SINGLE_EVENTEXECUTOR_PER_GROUP =
valueOf("SINGLE_EVENTEXECUTOR_PER_GROUP");
/**
* Creates a new {@link ChannelOption} with the specified unique {@code name}.
创建通道选项
*/
private ChannelOption(int id, String name) {
super(id, name);
}
@Deprecated
protected ChannelOption(String name) {
this(pool.nextId(), name);
}
/**
* Validate the value which is set for the {@link ChannelOption}. Sub-classes
* may override this for special checks.
校验通道选项的值
*/
public void validate(T value) {
if (value == null) {
throw new NullPointerException("value");
}
}
}
从上面可以看出通道选项实际为一个抽象常量，主要的操作都是委托给内部的常量池ConstantPool，
下面来看常量池的定义：
package io.netty.util;
import io.netty.util.internal.ObjectUtil;
import io.netty.util.internal.PlatformDependent;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
/**
* A pool of {@link Constant}s.
*
* @param <T> the type of the constant
*/
public abstract class ConstantPool<T extends Constant<T>> {
//常量集
private final ConcurrentMap<String, T> constants = PlatformDependent.newConcurrentHashMap();
//常量id生产器
private final AtomicInteger nextId = new AtomicInteger(1);
/**
* Shortcut of {@link #valueOf(String) valueOf(firstNameComponent.getName() + "#" + secondNameComponent)}.
获取firstNameComponent.getName() + "#" + secondNameComponent对应的常量
*/
public T valueOf(Class<?> firstNameComponent, String secondNameComponent) {
if (firstNameComponent == null) {
throw new NullPointerException("firstNameComponent");
}
if (secondNameComponent == null) {
throw new NullPointerException("secondNameComponent");
}
return valueOf(firstNameComponent.getName() + '#' + secondNameComponent);
}
/**
* Returns the {@link Constant} which is assigned to the specified {@code name}.
* If there's no such {@link Constant}, a new one will be created and returned.
* Once created, the subsequent calls with the same {@code name} will always return the previously created one
* (i.e. singleton.)
*返回name对应常量
* @param name the name of the {@link Constant}
*/
public T valueOf(String name) {
checkNotNullAndNotEmpty(name);
return getOrCreate(name);
}
/**
* Get existing constant by name or creates new one if not exists. Threadsafe
*获取name对应的常量，没有则创建
* @param name the name of the {@link Constant}
*/
private T getOrCreate(String name) {
T constant = constants.get(name);
if (constant == null) {
final T tempConstant = newConstant(nextId(), name);
constant = constants.putIfAbsent(name, tempConstant);
if (constant == null) {
return tempConstant;
}
}
return constant;
}
/**
* Returns {@code true} if a {@link AttributeKey} exists for the given {@code name}.
检查name常量是否存在
*/
public boolean exists(String name) {
checkNotNullAndNotEmpty(name);
return constants.containsKey(name);
}
/**
* Creates a new {@link Constant} for the given {@code name} or fail with an
* {@link IllegalArgumentException} if a {@link Constant} for the given {@code name} exists.
创建name常量
*/
public T newInstance(String name) {
checkNotNullAndNotEmpty(name);
return createOrThrow(name);
}
/**
* Creates constant by name or throws exception. Threadsafe
*创建name对应的常量
* @param name the name of the {@link Constant}
*/
private T createOrThrow(String name) {
T constant = constants.get(name);
if (constant == null) {
final T tempConstant = newConstant(nextId(), name);
constant = constants.putIfAbsent(name, tempConstant);
if (constant == null) {
return tempConstant;
}
}
throw new IllegalArgumentException(String.format("'%s' is already in use", name));
}
private static String checkNotNullAndNotEmpty(String name) {
ObjectUtil.checkNotNull(name, "name");
if (name.isEmpty()) {
throw new IllegalArgumentException("empty name");
}
return name;
}
//创建常量实例
protected abstract T newConstant(int id, String name);
@Deprecated
public final int nextId() {
return nextId.getAndIncrement();
}
}
从上面可以看出常量池，实际上用一个并发Map来存放常量，所有的操作委托为Map。
再来看通道选项的父类，抽象常量
public class ChannelOption<T> extends AbstractConstant<ChannelOption<T>> {
package io.netty.util;
import java.util.concurrent.atomic.AtomicLong;
/**
* Base implementation of {@link Constant}.
*/
public abstract class AbstractConstant<T extends AbstractConstant<T>> implements Constant<T> {
private static final AtomicLong uniqueIdGenerator = new AtomicLong();
private final int id;//常量id
private final String name;//常量name
private final long uniquifier;//常量唯一识别号
/**
* Creates a new instance.
*/
protected AbstractConstant(int id, String name) {
this.id = id;
this.name = name;
this.uniquifier = uniqueIdGenerator.getAndIncrement();
}
@Override
public final String name() {
return name;
}
@Override
public final int id() {
return id;
}
@Override
public final String toString() {
return name();
}
@Override
public final int hashCode() {
return super.hashCode();
}
@Override
public final boolean equals(Object obj) {
return super.equals(obj);
}
@Override
public final int compareTo(T o) {
if (this == o) {
return 0;
}
@SuppressWarnings("UnnecessaryLocalVariable")
AbstractConstant<T> other = o;
int returnCode;
returnCode = hashCode() - other.hashCode();
if (returnCode != 0) {
return returnCode;
}
if (uniquifier < other.uniquifier) {
return -1;
}
if (uniquifier > other.uniquifier) {
return 1;
}
throw new Error("failed to compare two different constants");
}
}
//Constant
package io.netty.util;
/**
* A singleton which is safe to compare via the {@code ==} operator. Created and managed by {@link ConstantPool}.
*/
public interface Constant<T extends Constant<T>> extends Comparable<T> {
/**
* Returns the unique number assigned to this {@link Constant}.
*/
int id();
/**
* Returns the name of this {@link Constant}.
*/
String name();
}
再来看属性key
package io.netty.util;
/**
* Key which can be used to access {@link Attribute} out of the {@link AttributeMap}. Be aware that it is not be
* possible to have multiple keys with the same name.
*
* @param <T> the type of the {@link Attribute} which can be accessed via this {@link AttributeKey}.
*/
@SuppressWarnings("UnusedDeclaration") // 'T' is used only at compile time
public final class AttributeKey<T> extends AbstractConstant<AttributeKey<T>> {
//常量池
private static final ConstantPool<AttributeKey<Object>> pool = new ConstantPool<AttributeKey<Object>>() {
@Override
protected AttributeKey<Object> newConstant(int id, String name) {
return new AttributeKey<Object>(id, name);
}
};
/**
* Returns the singleton instance of the {@link AttributeKey} which has the specified {@code name}.
*/
@SuppressWarnings("unchecked")
public static <T> AttributeKey<T> valueOf(String name) {
return (AttributeKey<T>) pool.valueOf(name);
}
/**
* Returns {@code true} if a {@link AttributeKey} exists for the given {@code name}.
*/
public static boolean exists(String name) {
return pool.exists(name);
}
/**
* Creates a new {@link AttributeKey} for the given {@code name} or fail with an
* {@link IllegalArgumentException} if a {@link AttributeKey} for the given {@code name} exists.
*/
@SuppressWarnings("unchecked")
public static <T> AttributeKey<T> newInstance(String name) {
return (AttributeKey<T>) pool.newInstance(name);
}
@SuppressWarnings("unchecked")
public static <T> AttributeKey<T> valueOf(Class<?> firstNameComponent, String secondNameComponent) {
return (AttributeKey<T>) pool.valueOf(firstNameComponent, secondNameComponent);
}
private AttributeKey(int id, String name) {
super(id, name);
}
}
从上面来看属性key也是一个常量，内部用常量池存放属性常量。