src/com/ibm/matos/BatchAppender.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.ibm.matos;

import java.util.List;

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.common.TopicPartition;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;

public class BatchAppender implements RecordsProcessor {
    private static final Logger logger = Logger.getLogger(RecordsProcessor.class);
    private long first, last;
    private StringBuilder buffer;

    public BatchAppender() {
        first = -1;
        last = -1;
    }

    @Override
    public void processRecords(List<ConsumerRecord<byte[], byte[]>> records, TopicPartition tp) {
        if (buffer == null) {
            buffer = new StringBuilder();
        }
        if (first == -1) { // update 'first' only the first time
            first = records.get(0).offset();
        }
        last = records.get(0).offset() + records.size();

        logger.log(Level.INFO, "Processing " + records.size() + " records from " + tp + " starting from offset "
                + records.get(0).offset() + ":");
        for (ConsumerRecord<byte[], byte[]> record : records) {
            // processing goes here
            String msg = "[" + record.offset() + "] " + new String(record.value());
            buffer.append(msg + System.getProperty("line.separator"));
//          logger.log(Level.DEBUG, "   " + msg);
        }
    }

    public byte[] getBytes() {
        return buffer.toString().getBytes();
    }

    public long getFirst() {
        return first;
    }

    public long getLast() {
        return last;
    }

}