Netty客户端接入流程NioSocketChannel创建解析
作者：向南是个万人迷
前文传送门：Netty客户端处理接入事件handle创建
NioSocketChannel的创建
回到上一小节的read()方法
public void read() {
//必须是NioEventLoop方法调用的, 不能通过外部线程调用
assert eventLoop().inEventLoop();
//服务端channel的config
final ChannelConfig config = config();
//服务端channel的pipeline
final ChannelPipeline pipeline = pipeline();
//处理服务端接入的速率
final RecvByteBufAllocator.Handle allocHandle = unsafe().recvBufAllocHandle();
//设置配置
allocHandle.reset(config);
boolean closed = false;
Throwable exception = null;
try {
try {
do {
//创建jdk底层的channel
//readBuf用于临时承载读到链接
int localRead = doReadMessages(readBuf);
if (localRead == 0) {
break;
}
if (localRead < 0) {
closed = true;
break;
}
//分配器将读到的链接进行计数
allocHandle.incMessagesRead(localRead);
//连接数是否超过最大值
} while (allocHandle.continueReading());
} catch (Throwable t) {
exception = t;
}
int size = readBuf.size();
//遍历每一条客户端连接
for (int i = 0; i < size; i ++) {
readPending = false;
//传递事件, 将创建NioSokectChannel进行传递
//最终会调用ServerBootstrap的内部类ServerBootstrapAcceptor的channelRead()方法
pipeline.fireChannelRead(readBuf.get(i));
}
readBuf.clear();
allocHandle.readComplete();
pipeline.fireChannelReadComplete();
//代码省略
} finally {
//代码省略
}
}我们继续剖析int localRead = doReadMessages(readBuf)这一部分逻辑
我们首先看readBuf
private final List<Object> readBuf = new ArrayList<Object>();
这里只是简单的定义了一个ArrayList, doReadMessages(readBuf)方法就是将读到的链接放在这个list中, 因为这里是NioServerSocketChannel所以这走到了NioServerSocketChannel的doReadMessage()方法
跟到doReadMessage()方法中:
protected int doReadMessages(List<Object> buf) throws Exception {
//根据当前jdk底层的serverSocketChannel拿到jdk底层channel
SocketChannel ch = javaChannel().accept();
try {
if (ch != null) {
//封装成一个NioSokectChannel扔到buf中
buf.add(new NioSocketChannel(this, ch));
return 1;
}
} catch (Throwable t) {
//代码省略
}
return 0;
}jdk底层相关的内容
首先根据jdk的ServerSocketChannel拿到jdk的Channel, 熟悉Nio的小伙伴应该不会陌生
封装成一个NioSokectChannel扔到Readbuf中
这里的NioSocketChannel是对jdk底层的SocketChannel的包装, 我们看到其构造方法传入两个参数, this代表当前NioServerSocketChannel, ch代表jdk的SocketChannel
我们跟到NioSocketChannel的构造方法中:
public NioSocketChannel(Channel parent, SocketChannel socket) {
super(parent, socket);
config = new NioSocketChannelConfig(this, socket.socket());
}这里看到调用了父类构造方法, 传入两个参数, parent代表创建自身channel的, NioServerSocketChannel, socket代表jdk底层的socketChannel
跟到父类构造方法中
protected AbstractNioByteChannel(Channel parent, SelectableChannel ch) {
super(parent, ch, SelectionKey.OP_READ);
}其中SelectionKey.OP_READ代表其监听事件是读事件
继续跟父类的构造方法:
protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) {
super(parent);
this.ch = ch;
this.readInterestOp = readInterestOp;
try {
//设置为非阻塞
ch.configureBlocking(false);
} catch (IOException e) {
//代码省略
}
}这里初始化了自身成员变量ch, 就是jdk底层的SocketChannel, 并初始化了自身的监听事件readInterestOp, 也就是读事件
ch.configureBlocking(false)这一步熟悉nio的小伙伴也不陌生, 就是将jdk的SocketChannel设置为非阻塞
我们继续跟到父类构造方法中:
protected AbstractChannel(Channel parent) {
this.parent = parent;
id = newId();
unsafe = newUnsafe();
pipeline = newChannelPipeline();
}这里初始化parent, 也就是创建自身的NioServerSocketChannel, 并为自身创建了唯一id
初始化unsafe, 我们跟到newUnsafe()方法中
由于此方法是NioEventLoop调用的, 所以会走到其父类AbstractNioByteChannel的newUnsafe()
跟到newUnsafe()中:
protected AbstractNioUnsafe newUnsafe() {
return new NioByteUnsafe();
}这里创建了NioByteUnsafe对象, 所以NioSocketChannel对应的unsafe是NioByteUnsafe
继续往下跟, 我们看到其初始化了pipeline, 有关pipline的知识, 我们会在下一章节中讲到
回到NioSocketChannel中的构造方法:
public NioSocketChannel(Channel parent, SocketChannel socket) {
super(parent, socket);
config = new NioSocketChannelConfig(this, socket.socket());
}同NioServerSocketChannel一样, 这里也初始化了一个Config属性, 传入两个参数, 当前NioSocketChannel自身和jdk的底层SocketChannel的socket对象
我们跟进其构造方法
private NioSocketChannelConfig(NioSocketChannel channel, Socket javaSocket) {
super(channel, javaSocket);
}同样, 这个类是NioSocketChannel的内部类
继续跟父类构造方法:
public DefaultSocketChannelConfig(SocketChannel channel, Socket javaSocket) {
super(channel);
if (javaSocket == null) {
throw new NullPointerException("javaSocket");
}
//保存当前javaSocket
this.javaSocket = javaSocket;
//是否禁止Nagle算法
if (PlatformDependent.canEnableTcpNoDelayByDefault()) {
try {
setTcpNoDelay(true);
} catch (Exception e) {
}
}
}这里保存了SocketChannel的socket对象, 并且默认的情况禁止了Nagle算法, 有关Nagle, 感兴趣的同学可以学习下相关知识
继续跟到父类构造方法中:
public DefaultChannelConfig(Channel channel) {
this(channel, new AdaptiveRecvByteBufAllocator());
}又跟到到了我们熟悉的部分了, 也就是说, 无论NioServerSocketChannel和NioSocketChannel, 最后都会初始化DefaultChannelConfig, 并创建可变ByteBuf分配器, 我们之前小节对此做过详细剖析这里不再赘述, 这部分忘记的内容可以阅读之前小节内容进行回顾
这个分配器什么时候真正分配字节缓冲的呢?我们会在之后的章节进行详细剖析
至此我们剖析完成了NioSocketChannel的初始化过程
以上就是Netty客户端接入流程NioSocketChannel创建源码解析的详细内容，更多关于Netty客户端接入流程NioSocketChannel的资料请关注脚本之家其它相关文章！