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This project was born out of a need to validate all POJOs (Plain Old Java Object) are behaving correctly. This project has two main aspects to it: * Make Testing as easy as possible. * Simplifying identity management (hashCode / equals) using annotation.

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/*
 * Copyright (c) 2010-2013 Osman Shoukry
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the GNU Lesser General Public License as published by
 *    the Free Software Foundation, either version 3 of the License or any
 *    later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Lesser General Public License for more details.
 *
 *    You should have received a copy of the GNU Lesser General Public License
 *    along with this program.  If not, see .
 */

package com.openpojo.business.identity.impl;

import com.openpojo.business.annotation.BusinessKey;
import com.openpojo.business.exception.BusinessException;
import com.openpojo.business.identity.HashCodeGenerator;
import com.openpojo.business.utils.BusinessIdentityUtils;
import com.openpojo.business.utils.BusinessPojoHelper;
import com.openpojo.reflection.PojoField;

/**
 * This class is the default implementation for hash code generation.
 * The algorithm is simple and conforms to the java spec for hash code generation.
 * 

 * Please note that as per spec, two equal hash codes don't mean that objects are equal,
 * while two un-equal hash codes DO mean that the objects are not equal.
 * 

 *
 * @author oshoukry
 */

public class DefaultHashCodeGenerator implements HashCodeGenerator {

    private DefaultHashCodeGenerator() {
    }

    public static HashCodeGenerator getInstance() {
        return Instance.INSTANCE;
    }


    public int doGenerate(final Object object) {
        if (object == null) {
            throw BusinessException.getInstance("null parameter passed object=[null]");
        }

        final int prime = 31;
        int result = 1;

        for (PojoField pojoField : BusinessPojoHelper.getBusinessKeyFields(object.getClass())) {
            BusinessKey businessKey = pojoField.getAnnotation(BusinessKey.class);
            result = prime * result + BusinessIdentityUtils.getHashCode(pojoField, object, businessKey.caseSensitive());
        }
        return result;
    }

    private static class Instance {
        static final HashCodeGenerator INSTANCE = new DefaultHashCodeGenerator();
    }
}