将Handler封装为包装对象
newCtx = newContext(group, filterName(name, handler), handler);
这里比较难理解的就是这个，我们进入到newContext方法里面:
private AbstractChannelHandlerContext newContext(EventExecutorGroup group, String name, ChannelHandler handler) {
return new DefaultChannelHandlerContext(this, childExecutor(group), name, handler);
}
进入到 DefaultChannelHandlerContext类的源码里面:
DefaultChannelHandlerContext(
DefaultChannelPipeline pipeline, EventExecutor executor, String name, ChannelHandler handler) {
//调用父类进行掩码计算
super(pipeline, executor, name, handler.getClass());
//保存一个handler
this.handler = handler;
}
这里除了会保存一个handler还会调用父类，我们介入到父类里面：
AbstractChannelHandlerContext(DefaultChannelPipeline pipeline, EventExecutor executor,
String name, Class<? extends ChannelHandler> handlerClass) {
this.name = ObjectUtil.checkNotNull(name, "name");
this.pipeline = pipeline;
this.executor = executor;
//标识 是in还是out
this.executionMask = mask(handlerClass);
// 如果由EventLoop或给定的Executor驱动的驱动程序是OrderedEventExecutor的实例，则其顺序为。
ordered = executor == null || executor instanceof OrderedEventExecutor;
}
这里会保存一些属性，这些属性都是我们前面讲过的，大家自行分析下，我们重点关注掩码的计算:
this.executionMask = mask(handlehttp://www.diuxie.comrClass);
static int mask(Class<? extends ChannelHandler> clazz) {
//直接再缓存中取出
Map<Class<? extends ChannelHandler>, Integer> cache = MASKS.get();
Integer mask = cache.get(clazz);
//缓存中不存在
if (mask == null) {
mask = mask0(clazz);
cache.put(clazz, mask);
}
return mask;
}
先从缓存中取出，如果不存在就调用 mask0(clazz); 方法计算，然后再放进缓存，我们进入到 mask0(clazz);方法：
private static int mask0(Class<? extends ChannelHandler> handlerType) {
int mask = MASK_EXCEPTION_CAUGHT;
try {
if (ChannelInboundHandler.class.isAssignableFrom(handlerType)) {
// 如果是 ChannelInboundHandler 实例，所有 Inbound 事件置为 1
mask |= MASK_ALL_INBOUND;
//判断是否存在Skip注解 如果催你在这个跳过的注解 就移除这个
if (isSkippable(handlerType, "channelRegistered", ChannelHandlerContext.class)) {
mask &= ~MASK_CHANNEL_REGISTERED;
}
..................忽略类似的代码.....................
}
if (ChannelOutboundHandler.class.isAssignableFrom(handlerType)) {
mask |= MASK_ALL_OUTBOUND;
if (isSkippable(handlerType, "bind", ChannelHandlerContext.class,
SocketAddress.class, ChannelPromise.class)) {
mask &= ~MASK_BIND;
}
..................忽略类似的手游代码.....................
}
} catch (Exception e) {
..................忽略异常的代码.....................
}
return mask;
}
这会区分两种情况，一种是 ChannelInboundHandler类型的，一种是 ChannelOutboundHandler类型的，二者逻辑相同，我们以ChannelInboundHandler为例：
首先，再ChannelHandlerMask类里面定义了很多的预设掩码值:
/** * 以下是方法代表的掩码值 */ static final int MASK_EXCEPTION_CAUGHT = 1; /** * channelRegistered方法的掩码 */ static final int MASK_CHANNEL_REGISTERED = 1 << 1; /** * channelUnregistered方法的掩码 */ static final int MASK_CHANNEL_UNREGISTERED = 1 << 2; /** * 后面的以此类推 */ static final int MASK_CHANNEL_ACTIVE = 1 << 3; static final int MASK_CHANNEL_INACTIVE = 1 << 4; static final int MASK_CHANNEL_READ = 1 << 5; static final int MASK_CHANNEL_READ_COMPLETE = 1 << 6; static final int MASK_USER_EVENT_TRIGGERED = 1 << 7; static final int MASK_CHANNEL_WRITABILITY_CHANGED = 1 << 8; /** * bind方法的掩码 */ static final int MASK_BIND = 1 << 9; /** * connect方法的掩码 */ static final int MASK_CONNECT = 1 << 10; /** * 后面的以此类推 */ static final int MASK_DISCONNECT = 1 << 11; static final int MASK_CLOSE = 1 << 12; static final int MASK_DEREGISTER = 1 << 13; static final int MASK_READ = 1 << 14; static final int MASK_WRITE = 1 << 15; static final int MASK_FLUSH = 1 << 16; /** * 包含全部 Inbound方法的掩码 */ private static final int MASK_ALL_INBOUND = MASK_EXCEPTION_CAUGHT | MASK_CHANNEL_REGISTERED | MASK_CHANNEL_UNREGISTERED | MASK_CHANNEL_ACTIVE | MASK_CHANNEL_INACTIVE | MASK_CHANNEL_READ | MASK_CHANNEL_READ_COMPLETE | MASK_USER_EVENT_TRIGGERED | MASK_CHANNEL_WRITABILITY_CHANGED; /** * 包含全部 outbound方法的掩码 */ private static final int MASK_ALL_OUTBOUND = MASK_EXCEPTION_CAUGHT | MASK_BIND | MASK_CONNECT | MASK_DISCONNECT | MASK_CLOSE | MASK_DEREGISTER | MASK_READ | MASK_WRITE | MASK_FLUSH;
我们回到 mask0方法：
mask |= MASK_ALL_INBOUND;
一开始，我们会直接将一个handler的掩码计算为拥有全部方法的掩码！
if (isSkippable(handlerType, "channelRegistered", ChannelHandlerContext.class)) {
mask &= ~MASK_CHANNEL_REGISTERED;
}
判断该方法是否存在 Skip注解，如果存在就排除掉这个掩码！
整个逻辑执行完毕后，这个掩码就只会包含handler中没有被注解注解的方法掩码！