Android Open Source - spring-sync Copy Operation

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The source code is released under:

Apache License

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Java Source Code

/*
 * Copyright 2014 the original author or authors.
 */* w ww  .  j  av a  2s  .co  m*/
 * Licensed 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.springframework.sync;

import static org.springframework.sync.PathToSpEL.*;

/**
 * <p>
 * Operation to copy a value from the given "from" path to the given "path".
 * Will throw a {@link PatchException} if either path is invalid or if the object at the from path 
 * is not assignable to the given path.
 * </p>
 * 
 * <p>
 * NOTE: When dealing with lists, the copy operation may yield undesirable results.
 * If a list is produced from a database query, it's likely that the list contains items with a unique ID.
 * Copying an item in the list will result with a list that has a duplicate object, with the same ID.
 * The best case post-patch scenario is that each copy of the item will be saved, unchanged, to the database
 * and later queries for the list will not include the duplicate.
 * The worst case post-patch scenario is that a following operation changes some properties of the copy,
 * but does not change the ID.
 * When saved, both the original and the copy will be saved, but the last one saved will overwrite the first.
 * Effectively only one copy will survive post-save.
 * </p>
 * 
 * <p>
 * In light of this, it's probably a good idea to perform a "replace" after a "copy" to set the ID property
 * (which may or may not be "id").
 * </p>
 * 
 * @author Craig Walls
 */
public class CopyOperation extends FromOperation {

  /**
   * Constructs the copy operation
   * @param path The path to copy the source value to. (e.g., '/foo/bar/4')
   * @param from The source path from which a value will be copied. (e.g., '/foo/bar/5')
   */
  public CopyOperation(String path, String from) {
    super("copy", path, from);
  }
  
  @Override
  <T> void perform(Object target, Class<T> type) {
    addValue(target, pathToExpression(from).getValue(target));
  }
  
}

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