类匹配机制

1. SimpleChannelInboundHandler在构造时，会通过泛型获取要处理的消息类型
2. 在经过解码器处理后，netty会根据具体的消息类型，将其传递给能够处理该类型的 handler

工作流程

java">解码器 ---->消息类型判断  ----> 对应类型的SimpleChannelInboundHandler

实现原理

泛型类型获取

java">public abstract class SimpleChannelInboundHandler<I> extends ChannelInboundHandlerAdapter {private final TypeParameterMatcher matcher;protected SimpleChannelInboundHandler() {// 通过泛型获取要处理的消息类型matcher = TypeParameterMatcher.find(this, SimpleChannelInboundHandler.class, "I");}
}

消息类型匹配

java">public boolean acceptInboundMessage(Object msg) throws Exception {// 判断消息是否是当前处理器可以处理的类型return matcher.match(msg);
}

消息处理流程

java">@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {boolean release = true;try {// 检查消息类型是否匹配if (acceptInboundMessage(msg)) {@SuppressWarnings("unchecked")I imsg = (I) msg;// 如果匹配，调用 channelRead0 处理消息channelRead0(ctx, imsg);} else {// 如果不匹配，将消息传递给下一个处理器release = false;ctx.fireChannelRead(msg);}} finally {if (autoRelease && release) {ReferenceCountUtil.release(msg);}}
}