可以使用两个连续联接：

KStream streamAB = streamA.join(streamB, ...);
// either:
KStream streamABC = streamA.selectKey(...) // set to the key as in streamC
                           .join(streamC, ...);
// or:
KStream streamCNew = streamC.selectKey(...); // set to the key as in streamAB
KStream streamABC = streamA.join(streamCnew, ...);
// or:
KStream streamCNew = streamC.selectKey(...); // set to a new join key
KStream streamABC = streamA.selectKey(...) // set to a new join key
                           .join(streamC, ...);
streamABC.selectKey(/* extract grouping field and set as key */).to("outputTopic");