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'rapiddweller Common' is an open source Java library forked from Databene Commons by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * All rights reserved.
 *
 * 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 com.rapiddweller.common.accessor;

import com.rapiddweller.common.Accessor;

import java.util.ArrayList;
import java.util.List;

/**
 * Accessor implementation that caches the value it retrieves first
 * until it is manually invalidated.
 * Created: 11.03.2006 17:02:27
 *
 * @param  the object type to access
 * @param  the type of the value to get from the object
 * @author Volker Bergmann
 */
public class AccessorCache implements DependentAccessor {

  private final String name;
  private final Accessor realAccessor;
  private V cachedValue;
  private boolean valid;

  /**
   * Instantiates a new Accessor cache.
   *
   * @param name         the name
   * @param realAccessor the real accessor
   */
  public AccessorCache(String name, Accessor realAccessor) {
    this.realAccessor = realAccessor;
    this.name = name;
    this.valid = false;
  }

  // properties ------------------------------------------------------------------------------------------------------

  /**
   * Gets name.
   *
   * @return the name
   */
  public String getName() {
    return name;
  }

  /**
   * Is valid boolean.
   *
   * @return the boolean
   */
  public boolean isValid() {
    return valid;
  }

  /**
   * Invalidate.
   */
  public void invalidate() {
    valid = false;
  }

  // DependentAccessor interface -------------------------------------------------------------------------------------

  @Override
  public V getValue(C item) {
    if (!valid) {
      cachedValue = realAccessor.getValue(item);
      valid = true;
    }
    return cachedValue;
  }

  @Override
  @SuppressWarnings({"unchecked", "rawtypes"})
  public List> getDependencies() {
    if (realAccessor instanceof DependentAccessor) {
      return ((DependentAccessor) realAccessor).getDependencies();
    } else {
      return new ArrayList();
    }
  }

}