请问使用@DubboReference 如何触发onturn事件呢

@Method注解中用onreturn属性 但是该属性只会设置org.apache.dubbo.config.MethodConfig中的onreturn属性并不会设置其onreturnMethod属性
但是org.apache.dubbo.rpc.protocol.dubbo.filter.FutureFilter::fireReturnCallback中会进行两个属性的判空呢

if (onReturnMethod == null || onReturnInst == null) {
throw new IllegalStateException("service:" + invoker.getUrl().getServiceKey() + " has a onreturn callback config , but no such " + (onReturnMethod == null ? "method" : "instance") + " found. url:" + invoker.getUrl());
}

Start with the @DubboReference and @Method configuration, then trace MethodConfig into org.apache.dubbo.rpc.protocol.dubbo.filter.FutureFilter::fireReturnCallback. Reproduce the onreturn configuration and determine whether onReturnMethod and onReturnInst are populated; done means the expected callback behavior or a specific configuration defect is established.

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