//DegradeSlot.entry
@Override
public void entry(Context context, ResourceWrapper resourceWrapper, DefaultNode node, int count,
                  boolean prioritized, Object... args) throws Throwable {
    // 熔断降级检测
    performChecking(context, resourceWrapper);
    // 触发下一个节点
    fireEntry(context, resourceWrapper, node, count, prioritized, args);
}

// 获取到指定资源的所有流控规则
Collection<FlowRule> rules = ruleProvider.apply(resource.getName());
// 逐个应用流控规则。若无法通过则抛出异常，后续规则不再应用
if (rules != null) {
    for (FlowRule rule : rules) {
        if (!canPassCheck(rule, context, node, count, prioritized)) {
            // FlowException继承BlockException
            throw new FlowException(rule.getLimitApp(), rule);
        }
    }
}
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// 这里调用的apply方法就是FlowSlot中的对应方法
private final Function<String, Collection<FlowRule>> ruleProvider = new Function<String, Collection<FlowRule>>() {
    @Override
    public Collection<FlowRule> apply(String resource) {
        // Flow rule map should not be null.
        // 获取所有资源和对应的流控规则 key为资源名称，value为该资源对应的所有流控规则
        Map<String, List<FlowRule>> flowRules = FlowRuleManager.getFlowRuleMap();
        // 获取指定资源的流控规则
        return flowRules.get(resource);
    }
};