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A library for error handling in Kafka Streams.
There is a newer version: 1.5.0
/*
 * MIT License
 *
 * Copyright (c) 2020 bakdata
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package com.bakdata.kafka;

import org.apache.kafka.streams.KeyValue;

/**
 * A processed key-value is created upon capturing errors in a streams topology. It can either contain a successfully
 * processed value or the old key along with a {@link ProcessingError} describing the input value and the {@link
 * Exception} that has been thrown.
 *
 * @param  the type of the old key before applying the error capturer
 * @param  the type of the old value before applying the error capturer
 * @param  the type of the new value after applying the error capturer
 */
public interface ProcessedKeyValue {

    /**
     * This method serves as a utility method to extract errors from a previous key-value mapper step. It can be
     * used as a lambda method reference and simply delegates to {@link #getErrors()}. The new key is not relevant and
     * thus omitted.
     *
     * Usage example:
     * {@code
     * final KStream> input = ...;
     * final KStream> errors = input.flatMap(ProcessedKeyValue::getErrors);
     * }
     * 
     *
     * @param newKey the new key of a processed key-value pair. As this method extracts errors, the new key is not
     * relevant and omitted. It is only used as a parameter to use a method reference lambda when creating a streams
     * topology.
     * @param recordWithOldKey a processed key-value pair containing a successfully extracted record or a {@link
     * ProcessingError}
     * @param  the type of the old key before applying the error capturer
     * @param  the type of the old value before applying the error capturer
     * @param  the type of the new key after applying the error capturer
     * @param  the type of the new value after applying the error capturer
     * @return A single key-value pair containing the old key and a {@link ProcessingError} if an exception was thrown
     * upon processing the input key-value pair or an empty list
     */
    static  Iterable>> getErrors(
            @SuppressWarnings("unused") final KR newKey, final ProcessedKeyValue recordWithOldKey) {
        return recordWithOldKey.getErrors();
    }

    /**
     * Extract errors from a processed key-value. If an error is available, it will give information about the input
     * key, value, and the {@link Exception} that was thrown while attempting to map it to a new value.
     *
     * @return A single key-value pair containing the old key and a {@link ProcessingError} if an exception was thrown
     * upon processing the input key-value pair or an empty list
     */
    Iterable>> getErrors();

    /**
     * Extract successfully processed values from a processed key-value.
     *
     * @return A single value if processing was successful or an empty list;
     */
    Iterable getValues();
}