Netty ChannelPipeline 中的addFirst和addLast实现

最新推荐文章于 2025-06-22 15:31:33 发布

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本文探讨了Netty的DefaultChannelPipeline如何利用双向链表实现`addFirst`和`addLast`功能。通过分析`AbstractChannelHandlerContext`，揭示了其内部结构，包括ChannelHandler的inbound和outbound标识。文章深入解析了`addFirst`方法调用`addFirst0`的实现细节。

在DefaultChannelPipeline中使用双向链表实现addFirst和addLast逻辑

final class DefaultChannelPipeline implements ChannelPipeline {

    static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultChannelPipeline.class);

    @SuppressWarnings("unchecked")
    private static final WeakHashMap<Class<?>, String>[] nameCaches =
            new WeakHashMap[Runtime.getRuntime().availableProcessors()];

    static {
        for (int i = 0; i < nameCaches.length; i ++) {
            nameCaches[i] = new WeakHashMap<Class<?>, String>();
        }
    }

    final AbstractChannel channel;

    final AbstractChannelHandlerContext head;
    final AbstractChannelHandlerContext tail;

    private final Map<String, AbstractChannelHandlerContext> name2ctx =
        new HashMap<String, AbstractChannelHandlerContext>(4);

。。。。

可以看到AbstractChannelHandlerContext head和tail

进入看AbstractChannelHandlerContext ：

abstract class AbstractChannelHandlerContext extends DefaultAttributeMap implements ChannelHandlerContext {

    volatile AbstractChannelHandlerContext next;
    volatile AbstractChannelHandlerContext prev;

    private final boolean inbound;
    private final boolean outbound;
    private final AbstractChannel channel;
    private final DefaultChannelPipeline pipeline;
    private final String name;

。。。。}

可以看到是双向链表结构，并有ChannelHandler的类型标示：boolean inbound, outbound

具体看addFirst和addLast方法源码：

在addFirst中最终调用了addFirst0方法：

private void addFirst0(String name, AbstractChannelHandlerContext newCtx) {
    checkMultiplicity(newCtx);

    AbstractChannelHandlerContext nextCtx = head.next;
    newCtx.prev = head;
    newCtx.next = nextCtx;
    head.next = newCtx;
    nextCtx.prev = newCtx;

    name2ctx.put(name, newCtx);

    callHandlerAdded(newCtx);
}

在addLast中最终调用了addLast0方法：

private void addLast0(final String name, AbstractChannelHandlerContext newCtx) {
    checkMultiplicity(newCtx);

    AbstractChannelHandlerContext prev = tail.prev;
    newCtx.prev = prev;
    newCtx.next = tail;
    prev.next = newCtx;
    tail.prev = newCtx;

    name2ctx.put(name, newCtx);

    callHandlerAdded(newCtx);
}