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.arrow.flight;
  
  import java.util.Set;
  
  /** Tracks variables about the current request. */
  public interface RequestContext {
    /**
     * Register a variable and a value.
     *
     * @param key the variable name.
     * @param value the value.
     */
    void put(String key, String value);
  
    /**
     * Retrieve a registered variable.
     *
     * @param key the variable name.
     * @return the value, or null if not found.
     */
    String get(String key);
  
    /**
     * Retrieves the keys that have been registered to this context.
     *
     * @return the keys used in this context.
     */
    Set<String> keySet();
  
    /**
     * Deletes a registered variable.
     *
     * @return the value associated with the deleted variable, or null if the key doesn't exist.
     */
    String remove(String key);
  }
  