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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.bean;

import com.rapiddweller.common.ComparableComparator;
import com.rapiddweller.common.comparator.ComparatorFactory;

import java.util.Comparator;

/**
 * Compares JavaBeans by a property.
 * If a beanComparator is provided, this one is used for property comparison,
 * else the ComparatorFactory is queried for a Comparator.
 * Created: 06.01.2005 20:04:36
 *
 * @param  the type of objects to be compared
 * @author Volker Bergmann
 * @see ComparatorFactory
 */
public class BeanComparator implements Comparator {

  private final Comparator propertyComparator;
  private final PropertyAccessor propertyAccessor;

  // constructor -----------------------------------------------------------------------------------------------------

  /**
   * Instantiates a new Bean comparator.
   *
   * @param propertyName the property name
   */
  @SuppressWarnings({"unchecked", "rawtypes"})
  public BeanComparator(String propertyName) {
    this.propertyComparator = new ComparableComparator();
    try {
      this.propertyAccessor = PropertyAccessorFactory.getAccessor(propertyName);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Instantiates a new Bean comparator.
   *
   * @param comparedClass the compared class
   * @param propertyName  the property name
   */
  public BeanComparator(Class comparedClass, String propertyName) {
    this(comparedClass, propertyName, getComparator(comparedClass, propertyName));
  }

  /**
   * Instantiates a new Bean comparator.
   *
   * @param comparedClass the compared class
   * @param propertyName  the property name
   * @param comparator    the comparator
   */
  @SuppressWarnings("unchecked")
  public BeanComparator(Class comparedClass, String propertyName, Comparator comparator) {
    this.propertyComparator = (Comparator) comparator;
    try {
      this.propertyAccessor = PropertyAccessorFactory.getAccessor(comparedClass, propertyName);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  // interface -------------------------------------------------------------------------------------------------------

  @Override
  public int compare(E o1, E o2) {
    try {
      Object v1 = propertyAccessor.getValue(o1);
      Object v2 = propertyAccessor.getValue(o2);
      return propertyComparator.compare(v1, v2);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  // private helpers -------------------------------------------------------------------------------------------------

  @SuppressWarnings({"unchecked", "rawtypes"})
  private static Comparator getComparator(Class comparedClass, String propertyName) {
    PropertyAccessor propertyAccessor = PropertyAccessorFactory.getAccessor(comparedClass, propertyName);
    Comparator beanComparator = ComparatorFactory.getComparator(propertyAccessor.getValueType());
    if (beanComparator == null) {
      throw new IllegalArgumentException("Property '" + comparedClass.getName() + '.' + propertyName + "' " +
          "is expected to implement Comparable");
    }
    return beanComparator;
  }

}
    

    

    

            

    

            



    
    






    
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