Key::: abc
Value::: {"customerId":"abc", "rollNo": 7, "subject": "English", "mark": 98}

Key::: abc
Value::: {"customerId":"abc", "rollNo": "registerNo", "subject": "sub"}

Key::: abc
Value::: {"customerId":"abc", "registerNo": 7, "sub": "English", "mark": 98}

@Component

public class JoinMsg {

    msgLookup lookup;

    public JoinMsg(msgLookup lookup) {
        this.lookup = lookup;
    }

    interface dataProcessor {

        @Input("inputStream")
        KStream<?, ?> input1();

        @Input("globalTable")
        GlobalKTable<byte[], Object> input2();

        @Output("OutputStream")
        KStream<?, ?> output3();
    }

    @EnableBinding(dataProcessor.class)
    public static class msgLookup {
        @StreamListener
        @SendTo("OutputStream")
        public KStream<String, String> handle(@Input("inputStream") KStream<String, String> input, @Input("globalTable")GlobalKTable<String, String> table) {

            input.peek((key, value) -> System.out.println("Incoming Stream -- key: " + key + " --value: " + value));

            KStream<String, String> outStream = input.leftJoin(table, (k, v) -> k , (bTag, tTag) -> new tagLookup(tTag == null ? "customer" : tTag, bTag))
                    .map((tag, taglookup) -> new KeyValue<>(taglookup.gettTag(), taglookup.getbTag()))
                    .groupByKey(Serialized.with(Serdes.String(), Serdes.String()))
                    .reduce((a,b)-> a+b)
                    .toStream();

            outStream.peek((key, value) -> System.out.println("Outgoing Stream from 2nd part -- key: " + key + " --value: " + value));

            return outStream;
        }

        private class tagLookup {

            private final String tTag;
            private final String bTag;

            public tagLookup(String tTag, String bTag) {
                if (tTag == null || tTag.isEmpty()) {
                    throw new IllegalArgumentException("tTag must be set");
                }
                if (bTag == null || bTag.isEmpty()) {
                    throw new IllegalArgumentException("bTag must be set");
                }
                this.tTag = tTag;
                this.bTag = bTag;
            }
            public String gettTag() {
                return tTag;
            }

            public String getbTag() {
                return bTag;
            }
        }
    }
}