content: /*
   * 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 org.apache.kafka.connect.header;
  
  import org.apache.kafka.connect.data.Schema;
  
  /**
   * A {@link Header} is a key-value pair, and multiple headers can be included with the key, value, and timestamp in each Kafka message.
   * If the value contains schema information, then the header will have a non-null {@link #schema() schema}.
   * <p>
   * This is an immutable interface.
   */
  public interface Header {
  
      /**
       * The header's key, which is not necessarily unique within the set of headers on a Kafka message.
       *
       * @return the header's key; never null
       */
      String key();
  
      /**
       * Return the {@link Schema} associated with this header, if there is one. Not all headers will have schemas.
       *
       * @return the header's schema, or null if no schema is associated with this header
       */
      Schema schema();
  
      /**
       * Get the header's value as deserialized by Connect's header converter.
       *
       * @return the deserialized object representation of the header's value; may be null
       */
      Object value();
  
      /**
       * Return a new {@link Header} object that has the same key but with the supplied value.
       *
       * @param schema the schema for the new value; may be null
       * @param value  the new value
       * @return the new {@link Header}; never null
       */
      Header with(Schema schema, Object value);
  
      /**
       * Return a new {@link Header} object that has the same schema and value but with the supplied key.
       *
       * @param key the key for the new header; may not be null
       * @return the new {@link Header}; never null
       */
      Header rename(String key);
  }
  