Channel接口的定义如下:

package io.netty.channel

public interface Channel extends AttributeMap, Comparable<Channel> {
}

继承了AttributeMap接口用于提供Attribute的访问, 继承了Comparable接口用于???

TBD: 继承Comparable接口是为什么?

Channel接口方法定义

获取基础属性

ChannelId id()
Channel parent()
ChannelConfig config()
ChannelMetadata metadata(): 获取TCP参数配置

获取运行时属性

EventLoop eventLoop()
Channel.Unsafe unsafe()
ChannelPipeline pipeline()
ByteBufAllocator alloc()

获取状态

boolean isOpen()
boolean isRegistered()
boolean isActive()
boolean isWritable()

获取和网络相关属性

SocketAddress localAddress()
SocketAddress remoteAddress()

获取各种Future和Promise

ChannelFuture closeFuture()
ChannelPromise newPromise()
ChannelProgressivePromise newProgressivePromise()
ChannelFuture newSucceededFuture()
ChannelFuture newFailedFuture(Throwable cause)
ChannelPromise voidPromise()

IO操作

ChannelFuture bind(SocketAddress localAddress)
ChannelFuture bind(SocketAddress localAddress, ChannelPromise promise)
ChannelFuture connect(SocketAddress remoteAddress)
ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress)
ChannelFuture connect(SocketAddress remoteAddress, ChannelPromise promise)
ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise)
ChannelFuture disconnect()
ChannelFuture disconnect(ChannelPromise promise)
ChannelFuture close()
ChannelFuture close(ChannelPromise promise)
ChannelFuture deregister()
ChannelFuture deregister(ChannelPromise promise)
Channel read()
ChannelFuture write(Object msg)
ChannelFuture write(Object msg, ChannelPromise promise)
Channel flush()
ChannelFuture writeAndFlush(Object msg)
ChannelFuture writeAndFlush(Object msg, ChannelPromise promise)

Unsafe

在Channel接口内部定义了一个Unsafe接口, 然后提供了一个unsafe()用于或者这个Channel实例关联的Unsafe对象实例:

public interface Channel extends AttributeMap, Comparable<Channel> {
    ......
    Unsafe unsafe();
    ......
    interface Unsafe {......}
}

这个Unsafe接口相关的内容后面再详细讲.

其他Channel接口

在Channel继承结构中, ServerChannel/ServerSocketChannel/SocketChannel 三个interface继承自Channel.

ServerChannel

ServerChannel 仅仅是一个标识接口, 没有任何实质内容. 代码也只是简单的有个申明:

public interface ServerChannel extends Channel { }

ServerSocketChannel

ServerSocketChannel从ServerChannel继承, 内容也很少,只是覆盖了几个定义在Channel的方法, 修改了函数的返回类型, 用更具体的子类型替代了Channel接口中定义的基础类型:

public interface ServerSocketChannel extends ServerChannel {
    @Override
    ServerSocketChannelConfig config();            // return ChannelConfig in Channel
    @Override
    InetSocketAddress localAddress();            // return SocketAddress in Channel
    @Override
    InetSocketAddress remoteAddress();            // return SocketAddress in Channel
}

SocketChannel

SocketChannel内容也不多:

和ServerSocketChannel一样,覆盖了几个定义在Channel的方法, 修改了函数的返回类型, 用更具体的子类型替代了Channel接口中定义的基础类型:

 public interface SocketChannel extends Channel {
     @Override
     ServerSocketChannel parent();            // return Channel in Channel

     @Override
     SocketChannelConfig config();            // return ChannelConfig in Channel
     @Override
     InetSocketAddress localAddress();        // return SocketAddress in Channel
     @Override
     InetSocketAddress remoteAddress();        // return SocketAddress in Channel
     ......

注意 parent() 的修改, SocketChannel应该都是从ServerSocketChannel中accept得到,所以它的parent总应该是一个 ServerSocketChannel.

定义了几个和socket相关的方法:

 public interface SocketChannel extends Channel {
     ......
     boolean isInputShutdown();

     boolean isOutputShutdown();

     ChannelFuture shutdownOutput();

     ChannelFuture shutdownOutput(ChannelPromise future);

接口Channel