SimpleChannelInboundHandler 源码笔记

io.netty.util.internal.TypeParameterMatcher

定义： 类型参数匹配器
功能： 用于判断 SimpleChannelInboundHandler<?> 中传入参数是否是该handler要处理的 message

io.netty.channel.SimpleChannelInboundHandler

public abstract class SimpleChannelInboundHandler<I> extends ChannelInboundHandlerAdapter {
    private final TypeParameterMatcher matcher;
    private final boolean autoRelease;

    protected SimpleChannelInboundHandler() {
        this(true);
    }

    protected SimpleChannelInboundHandler(boolean autoRelease) {
        this.matcher = TypeParameterMatcher.find(this, SimpleChannelInboundHandler.class, "I");
        this.autoRelease = autoRelease;
    }

    protected SimpleChannelInboundHandler(Class<? extends I> inboundMessageType) {
        this(inboundMessageType, true);
    }

    // 获取iboundMEssageType参数的 类型 matcher, 自动release 为 true， 这是于ChannelInboundHandler 的不同点，后者需要手动释放
    protected SimpleChannelInboundHandler(Class<? extends I> inboundMessageType, boolean autoRelease) {
        this.matcher = TypeParameterMatcher.get(inboundMessageType);
        this.autoRelease = autoRelease;
    }

    public boolean acceptInboundMessage(Object msg) throws Exception {
        return this.matcher.match(msg);
    }

    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        boolean release = true;

        try {
            // 如果接收到的参数是匹配类型，则处理
            if (this.acceptInboundMessage(msg)) {
                this.channelRead0(ctx, msg);
            } else {
                // 不匹配交给下一个handler 处理
                release = false;
                ctx.fireChannelRead(msg);
            }
        } finally {
            if (this.autoRelease && release) {
                // 引用计数减一
                ReferenceCountUtil.release(msg);
            }

        }

    }
    // 由子类实现
    protected abstract void channelRead0(ChannelHandlerContext var1, I var2) throws Exception;
}

事例：

/**
 * @Author Mario
 * @Date 2022-03-24 19:42
 * @Version ：
 * @Description : 专门处理LoginRequestPacket 对象的请求，处理不了的直接传给下一个handler, 避免过多的if/else 处理不同的请求
 */
public class LoginRequestHandler extends SimpleChannelInboundHandler<LoginRequestPacket> {

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, LoginRequestPacket packet) throws Exception {
        LoginResponsePacket loginResponsePacket = new LoginResponsePacket();
        loginResponsePacket.setVersion(packet.getVersion());
        if (valid(packet)) {
            // 校验成功
            loginResponsePacket.setSuccess(true);
            System.out.println(new Date() + ": 登录成功");

        } else {
            // 失败
            loginResponsePacket.setReason("账号密码不正确");
            loginResponsePacket.setSuccess(false);
            System.out.println(new Date() + ": 登录失败");
        }
        // 登录响应
//        ByteBuf out = PacketCodeC.INSTANCE.encode(ctx.alloc(), loginResponsePacket);
        ctx.channel().writeAndFlush(loginResponsePacket);
    }
    
}

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