1、Channel主要成员和方法

几乎所有的Netty通道都继承了AbstractChannel抽象类，都拥有parent和pipeline两个成员
主要成员：

  • parent
    • 对于连接监听通道（如NioServerSocketChannel），其parent属性为null
    • 对于传输通道（如NioSocketChannel），其parent属性为接收到该连接的通道
  • pipeline
    • 表示该通道的处理器流水线，该属性被初始化为DefaultChannelPipeline的实例 ```json //父通道 private final Channel parent; private final ChannelId id; private final Unsafe unsafe; private final DefaultChannelPipeline pipeline;

protected AbstractChannel(Channel parent) { this.parent = parent; this.id = this.newId(); //新建一个底层的NIO通道，完成实际的IO操作 this.unsafe = this.newUnsafe(); //新建一条通道流水线 this.pipeline = this.newChannelPipeline(); }

  1. protected AbstractChannel(Channel parent, ChannelId id) {
  2.     this.parent = parent;
  3.     this.id = id;
  4.     this.unsafe = this.newUnsafe();
  5.     this.pipeline = this.newChannelPipeline();
  6. }
  4. **接口中定义的重要方法：**
  6. - `ChannelFuture connect(SocketAddress remoteAddress)`
  7.    - 连接远程服务器，调用后立即返回，返回值为执行连接操作的异步任务
  8. - `ChannelFuture bind(SocketAddress localAddress)`
  9.    - 绑定监听地址<br />
  10. - `ChannelFuture close()`
  11.    - 关闭通道连接，返回连接关闭的异步任务
  12. - `ChannelFuture closeFuture() `
  13.    - 用来处理 channel 的关闭，sync 方法作用是同步等待 channel 关闭；而 addListener 方法是异步等待 channel 关闭
  14. - `Channel read()`
  15.    - 读取通道数据，并启动入站处理<br />
  16. - `ChannelFuture write(Object msg)`
  17.    - 启动出站流水处理，将最终处理数据结果写到底层通道<br />
  18. - `Channel flush()`
  19.    - 将缓冲区的数据立即写出到对端<br />
  22. <a name="NQIDj"></a>
  23. # 2、EmbeddedChannel
  25. 开发人员可以通过EmbeddedChannel方便快速的进行ChannelHandler业务处理器的单元测试，避免每开发一个业务处理器都进行服务器和客户端的重复启动。
  28. ![](https://cdn.nlark.com/yuque/0/2021/png/1911003/1622950440129-4f8bc5e5-cd37-445c-8cd3-407a289c4186.png#align=left&display=inline&height=436&margin=%5Bobject%20Object%5D&originHeight=436&originWidth=920&size=0&status=done&style=none&width=920)
  31. ```json
  32. @Slf4j
  33. public class TestEmbeddedChannel {
  35.     public static void main(String[] args) {
  38.         ChannelInboundHandlerAdapter h1 =    new ChannelInboundHandlerAdapter(){
  39.             @Override
  40.             public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
  41.                 log.info("入站处理器h1");
  42.                 super.channelRead(ctx, msg);
  43.             }
  44.         };
  46.         ChannelInboundHandlerAdapter h2 =    new ChannelInboundHandlerAdapter(){
  47.             @Override
  48.             public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
  49.                 log.info("入站处理器h2");
  50.                 super.channelRead(ctx, msg);
  51.             }
  52.         };
  54.         ChannelOutboundHandlerAdapter h3 = new ChannelOutboundHandlerAdapter(){
  55.             @Override
  56.             public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
  57.                 log.info("出站处理器h3");
  58.                 super.write(ctx, msg, promise);
  59.             }
  60.         };
  62.         ChannelOutboundHandlerAdapter h4 = new ChannelOutboundHandlerAdapter(){
  63.             @Override
  64.             public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
  65.                 log.info("出站处理器h4");
  66.                 super.write(ctx, msg, promise);
  67.             }
  68.         };
  70.         EmbeddedChannel embeddedChannel = new EmbeddedChannel(h1,h2,h3,h4);
  72.         embeddedChannel.writeInbound(ByteBufAllocator.DEFAULT.buffer().writeBytes("hello".getBytes(StandardCharsets.UTF_8)));
  73.         embeddedChannel.writeOutbound(ByteBufAllocator.DEFAULT.buffer().writeBytes("hello".getBytes(StandardCharsets.UTF_8)));
  74.     }
  75. }