Unsafe是托委訪問socket，那么Channel是直接提供給開發(fā)者使用的
Channel 主要有兩個實現(xiàn) NioServerSocketChannel同NioSocketChannel 致于其它不常用不在研究范圍內(nèi)
NioServerSocketChannel 是給server用的，程序由始至終只有一個NioServerSocketChannel
NioSocketChannel 是給客戶端用的，每個連接生成一個NioSocketChannel 對象
NioSocketChannel同NioSocketChannel的繼承關(guān)系
NioSocketChannel -> AbstractNioByteChannel -> AbstractNioChannel -> AbstractChannel
NioServerSocketChannel -> AbstractNioMessageChannel-> AbstractNioChannel -> AbstractChannel
小提示：如果看文字不夠直觀可以在eclipse里按快捷鍵 選擇類 ctrl+t
channel有unsafe相應(yīng)的實現(xiàn)類，反之亦是。其實功能是很簡單的，劃分太多對象目的是對某部分功能重用，有時也可能因過渡設(shè)計造成
對于channel我們主要分析 I/O read/write操作
NioServerSocketChannel AbstractNioMessageChannel SelectorProvider DEFAULT_SELECTOR_PROVIDER = (= NioServerSocketChannelConfig( doReadMessages(List<Object> buf) = (ch != buf.add( NioSocketChannel( 1 0 doWrite(ChannelOutboundBuffer in)
public class NioSocketChannel extends AbstractNioByteChannel implements io.netty.channel.socket.SocketChannel { public NioSocketChannel(Channel parent, SocketChannel socket) { super(parent, socket);
config = new NioSocketChannelConfig(this, socket.socket());
}
//////////////////////////////這部分是unsafe底層調(diào)用上層的實現(xiàn)////////////////////////////////////////////// @Override protected int doReadBytes(ByteBuf byteBuf) throws Exception { final RecvByteBufAllocator.Handle allocHandle = unsafe().recvBufAllocHandle(); //這里設(shè)置byteBuf寫入數(shù)據(jù)坐標 allocHandle.attemptedBytesRead(byteBuf.writableBytes()); return byteBuf.writeBytes(javaChannel(), allocHandle.attemptedBytesRead());
}
@Override protected int doWriteBytes(ByteBuf buf) throws Exception { final int expectedWrittenBytes = buf.readableBytes(); return buf.readBytes(javaChannel(), expectedWrittenBytes);
}
@Override protected void doWrite(ChannelOutboundBuffer in) throws Exception { for (;;) { int size = in.size(); //沒有數(shù)據(jù)退出
if (size == 0) {
clearOpWrite(); break;
}
long writtenBytes = 0; //記錄寫數(shù)據(jù)size
boolean done = false; //是否完成
boolean setOpWrite = false;
ByteBuffer[] nioBuffers = in.nioBuffers(); int nioBufferCnt = in.nioBufferCount(); long expectedWrittenBytes = in.nioBufferSize();
SocketChannel ch = javaChannel(); //這里有三種分支處理 //如果沒有ByteBuffer 有可能只發(fā)送幾個byte //1跟default邏輯其實是一樣的
switch (nioBufferCnt) { case 0: //調(diào)用父類 AbstractNioByteChannel doWrite，邏輯基本相同，不同的是AbstractNioByteChannel處理的是byte 實現(xiàn)調(diào)用的是 doWriteBytes(ByteBuf buf)方法。。。
super.doWrite(in); return; case 1: //這里只循環(huán)16次，可以看出是復制下面代碼的哈。。。
ByteBuffer nioBuffer = nioBuffers[0]; for (int i = config().getWriteSpinCount() - 1; i >= 0; i --) { final int localWrittenBytes = ch.write(nioBuffer); if (localWrittenBytes == 0) {
setOpWrite = true; break;
}
expectedWrittenBytes -= localWrittenBytes;
writtenBytes += localWrittenBytes; if (expectedWrittenBytes == 0) {
done = true; break;
}
} break; default: //多個ByteBuffer時跟上面邏輯一樣
for (int i = config().getWriteSpinCount() - 1; i >= 0; i --) { final long localWrittenBytes = ch.write(nioBuffers, 0, nioBufferCnt); if (localWrittenBytes == 0) {
setOpWrite = true; break;
}
expectedWrittenBytes -= localWrittenBytes;
writtenBytes += localWrittenBytes; if (expectedWrittenBytes == 0) {
done = true; break;
}
} break;
} // Release the fully written buffers, and update the indexes of the partially written buffer. in.removeBytes(writtenBytes); if (!done) { // Did not write all buffers completely. incompleteWrite(setOpWrite); break;
}
}
}
}
public abstract class AbstractChannel extends DefaultAttributeMap implements Channel { //生成NioSocketChannel時就綁定 unsafe pipeline
protected AbstractChannel(Channel parent) { this.parent = parent;
id = newId();
unsafe = newUnsafe();
pipeline = newChannelPipeline();
}
}protected abstract class AbstractUnsafe implements Unsafe { private void register0(ChannelPromise promise) { try { if (!promise.setUncancellable() || !ensureOpen(promise)) { return;
} boolean firstRegistration = neverRegistered;
doRegister(); // doRegister 是調(diào)用 AbstractNioChannel selectionKey = javaChannel().register(eventLoop().selector, 0, this);
neverRegistered = false;
registered = true; //這里是添加 Handler 每個Handler會生成一個Context pipeline.invokeHandlerAddedIfNeeded();
safeSetSuccess(promise); //通知Handler Registered pipeline.fireChannelRegistered(); if (isActive()) { if (firstRegistration) { //通知Handler Active pipeline.fireChannelActive();
} else if (config().isAutoRead()) {
beginRead();
}
}
} catch (Throwable t) { //....... }
}
}
小結(jié)：看似很復雜的Channel實現(xiàn)其實沒想象難，大多數(shù)讀寫坐標記錄交給ByteBuf處理掉了
1.server每個client連接轉(zhuǎn)換成NioSocketChannel對象
2.構(gòu)建NioSocketChannel時就已經(jīng)生成 unsafe、pipeline
| 作者: | solq |
| 博客地址： | http://www.cnblogs.com/solq111 |
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http://www.cnblogs.com/solq111/p/7066208.html
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