mask 是一个静态方法，来自于 ChannelHandlerMask 类
// ChannelHandlerMask.java // 省略部分代码 /** * Return the {@code executionMask}. */ static int mask(Class<? extends ChannelHandler> clazz) { // Try to obtain the mask from the cache first. If this fails calculate it and put it in the cache for fast // lookup in the future. Map<Class<? extends ChannelHandler>, Integer> cache = MASKS.get(); Integer mask = cache.get(clazz); if (mask == null) { mask = mask0(clazz); cache.put(clazz, mask); } return mask; } /** * Calculate the {@code executionMask}. */ private static int mask0(Class<? extends ChannelHandler> handlerType) { int mask = MASK_EXCEPTION_CAUGHT; try { if (ChannelInboundHandler.class.isAssignableFrom(handlerType)) { mask |= MASK_ALL_INBOUND; if (isSkippable(handlerType, "channelRegistered", ChannelHandlerContext.class)) { mask &= ~MASK_CHANNEL_REGISTERED; } if (isSkippable(handlerType, "channelUnregistered", ChannelHandlerContext.class)) { mask &= ~MASK_CHANNEL_UNREGISTERED; } if (isSkippable(handlerType, "channelActive", ChannelHandlerContext.class)) { mask &= ~MASK_CHANNEL_ACTIVE; } if (isSkippable(handlerType, "channelInactive", ChannelHandlerContext.class)) { mask &= ~MASK_CHANNEL_INACTIVE; } if (isSkippable(handlerType, "channelRead", ChannelHandlerContext.class, Object.class)) { mask &= ~MASK_CHANNEL_READ; } if (isSkippable(handlerType, "channelReadComplete", ChannelHandlerContext.class)) { mask &= ~MASK_CHANNEL_READ_COMPLETE; } if (isSkippable(handlerType, "channelWritabilityChanged", ChannelHandlerContext.class)) { mask &= ~MASK_CHANNEL_WRITABILITY_CHANGED; } if (isSkippable(handlerType, "userEventTriggered", ChannelHandlerContext.class, Object.class)) { mask &= ~MASK_USER_EVENT_TRIGGERED; } } if (ChannelOutboundHandler.class.isAssignableFrom(handlerType)) { mask |= MASK_ALL_OUTBOUND; if (isSkippable(handlerType, "bind", ChannelHandlerContext.class, SocketAddress.class, ChannelPromise.class)) { mask &= ~MASK_BIND; } if (isSkippable(handlerType, "connect", ChannelHandlerContext.class, SocketAddress.class, SocketAddress.class, ChannelPromise.class)) { mask &= ~MASK_CONNECT; } if (isSkippable(handlerType, "disconnect", ChannelHandlerContext.class, ChannelPromise.class)) { mask &= ~MASK_DISCONNECT; } if (isSkippable(handlerType, "close", ChannelHandlerContext.class, ChannelPromise.class)) { mask &= ~MASK_CLOSE; } if (isSkippable(handlerType, "deregister", ChannelHandlerContext.class, ChannelPromise.class)) { mask &= ~MASK_DEREGISTER; } if (isSkippable(handlerType, "read", ChannelHandlerContext.class)) { mask &= ~MASK_READ; } if (isSkippable(handlerType, "write", ChannelHandlerContext.class, Object.class, ChannelPromise.class)) { mask &= ~MASK_WRITE; } if (isSkippable(handlerType, "flush", ChannelHandlerContext.class)) { mask &= ~MASK_FLUSH; } } if (isSkippable(handlerType, "exceptionCaught", ChannelHandlerContext.class, Throwable.class)) { mask &= ~MASK_EXCEPTION_CAUGHT; } } catch (Exception e) { // Should never reach here. PlatformDependent.throwException(e); } return mask; } @SuppressWarnings("rawtypes") private static boolean isSkippable( final Class<?> handlerType, final String methodName, final Class<?>... paramTypes) throws Exception { return AccessController.doPrivileged(new PrivilegedExceptionAction<Boolean>() { @Override public Boolean run() throws Exception { Method m; try { m = handlerType.getMethod(methodName, paramTypes); } catch (NoSuchMethodException e) { if (logger.isDebugEnabled()) { logger.debug( "Class {} missing method {}, assume we can not skip execution", handlerType, methodName, e); } return false; } return m != null && m.isAnnotationPresent(Skip.class); } }); } // 省略部分代码