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HttpClient-based client for Riak

There is a newer version: 2.1.1

/*
 * This file is provided 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.basho.riak.client.api.cap;

/**
 * A Mutation is some encapsulated logic that generates a new value from some previous value
 *
 * 
 * Big thanks to Coda Hale from Yammer for this. Modelling your data as
 * logically monotonic makes store operations more predictable in a distributed
 * environment. Basically changing data *based on its
 * contents* and your logic. As the simplest example:
 *
 * Rather than creating a riak object with a value of (say 25) you create a
 * Mutation that adds 1 to whatever value comes from Riak
 * 
 * Allows for a store operation not to occur
 * if the object it is being applied to is not modified.
 *
 * 
 * By implementing this interface you can avoid a store operation from occurring
 * if the object it is be applied to is not modified.
 * 
 * For example:
 * 
 * Mutation<IRiakObject> m = new Mutation<IRiakObject>() {
 *     private boolean modified;
 *
 *     {@literal @}Override
 *     IRiakObject apply(IRiakObject original) {
 *          // I didn't do anything!
 *          modifed = false;
 *     }
 *
 *     {@literal @}Overrive
 *     boolean hasMutated() {
 *         return modified;
 *     }
 * };
 * 

 *
 *
 * @author russell
 * @author gmedina
 */
public interface Mutation {
  /**
   * Applies a mutation to the original value passed in
   *
   * @param original
   *            the value to update.
   * @return the mutated value.
   */
  T apply(T original);

  /**
   * Returns true if the mutation has actually created a change that must
   * be stored back to Riak.
   *
   * @return true if mutated, false otherwise
   */
  public boolean hasMutated();

}