UDAF example

udaf.java

package com.myorg.ksql.udaf;

import io.confluent.ksql.function.udaf.UdafFactory;
import io.confluent.ksql.function.udf.UdfDescription;

@UdfDescription(name = "totalStringLength", author = "Confluent", version = "1.0")
public class TotalStringLength {

  @UdafFactory(description = "sums the length of strings")
  public static Udaf<String, Long> createSumLengthString() {
    return new Udaf<String, Long>() {
      @Override
      public Long initialize() {
        return 0L;
      }

      @Override
      public Long aggregate(final String s, final Long aggregate) {
        return aggregate + s.length();
      }

      @Override
      public Long merge(final Long aggOne, final Long aggTwo) {
        return aggOne + aggTwo;
      }
    };
  }
}