[jira] Created: (LANG-449) Implement equals, hashCode and toString replacement

Implement equals, hashCode and toString replacement
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                 Key: LANG-449
                 URL: https://issues.apache.org/jira/browse/LANG-449
             Project: Commons Lang
          Issue Type: Improvement
            Reporter: Vincenzo Vitale
            Priority: Minor


In my company (TomTom), we have internally developed a replacement of the equals, hashcode and toString methods.

The base idea is to use the annotation @BusinessObject at the class level and @BusinessField at field level. Then what developers normally do is to override the three methods delegating to the utility methods:

@Override
public boolean equals(Object obj) { return BeanUtils.equals(this, obj); }

@Override
public int hashCode() { return BeanUtils.hashCode(this); }

@Override
public String toString() { return BeanUtils.toString(this); }

And i.e. the method signature of equals is:

/**

    * Compare two @BusinessObject beans comparing only the {@link BusinessField}
    * annotated fields.
    *
    * @param firstBean First bean to compare.
    * @param secondBean Second bean to compare.
    * @return The equals result.
    * @throws IllegalArgumentException If one of the beans compared is not an
    * instance of a {@link BusinessObject} annotated class.
      */
      public static boolean equals(Object firstBean, Object secondBean);

In the last versions of EqualsBuilder now there is the new method reflectionEquals... but there is no a way to specify what to include in the comparison. With our two annotations we are able to let developers exactly define what need to be included in a Business comparison, as i.e. normally required by persistence framework like hibernate.

The current implementation can also handle more complex case, comparing correctly totally different kind of objects.

For example if all my business logic cares only about the color, I can define:

@BusinessObject
public class Cat{

}

public class ColouredCat extends Cat{ @BusinessField private String color; getter/setter }

@BusinessObject
public class SunSet{ @BusinessField private String color="red"; getter/setter }

and then compare any instance of ColouredCat with a Sunset instance, finding out that the redColouredCat is (for my business logic) equal to a default instance of a Sunset. And also more tricky cases are handled (different BusinessFields, no BusinessObject annotation and so on).

We intensively use Hibernate and the utility demonstrated to work fine with CGLIB proxies

We always thought about the possibility to create a new Open Source project but then it was decided it would be better adding the feature to an already well know open source project...

If you are interested I can send you more details. How can we (me more one other developer) eventually became committers?

Thanks in advance,
Vicio.

P.s.: an utility method to automatically populate the BusinessFields of a BusinessObject is also implemented.

P.s.2: In the meanwhile I started creating a new OpenSource project here: http://code.google.com/p/simplestuff/ 

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Henri Yandell commented on LANG-449:
------------------------------------

Sounds very interesting. Something to look at for 3.0 I think.

Committership occurs as a function of an individual showing they are committed. Definitely helps to be writing new features like this in my opinion.

> Implement equals, hashCode and toString replacement
> ---------------------------------------------------
>
>                 Key: LANG-449
>                 URL: https://issues.apache.org/jira/browse/LANG-449
>             Project: Commons Lang
>          Issue Type: Improvement
>            Reporter: Vincenzo Vitale
>            Priority: Minor
>
> In my company (TomTom), we have internally developed a replacement of the equals, hashcode and toString methods.
> The base idea is to use the annotation @BusinessObject at the class level and @BusinessField at field level. Then what developers normally do is to override the three methods delegating to the utility methods:
> @Override
> public boolean equals(Object obj) { return BeanUtils.equals(this, obj); }
> @Override
> public int hashCode() { return BeanUtils.hashCode(this); }
> @Override
> public String toString() { return BeanUtils.toString(this); }
> And i.e. the method signature of equals is:
> /**
>     * Compare two @BusinessObject beans comparing only the {@link BusinessField}
>     * annotated fields.
>     *
>     * @param firstBean First bean to compare.
>     * @param secondBean Second bean to compare.
>     * @return The equals result.
>     * @throws IllegalArgumentException If one of the beans compared is not an
>     * instance of a {@link BusinessObject} annotated class.
>       */
>       public static boolean equals(Object firstBean, Object secondBean);
> In the last versions of EqualsBuilder now there is the new method reflectionEquals... but there is no a way to specify what to include in the comparison. With our two annotations we are able to let developers exactly define what need to be included in a Business comparison, as i.e. normally required by persistence framework like hibernate.
> The current implementation can also handle more complex case, comparing correctly totally different kind of objects.
> For example if all my business logic cares only about the color, I can define:
> @BusinessObject
> public class Cat{
> }
> public class ColouredCat extends Cat{ @BusinessField private String color; getter/setter }
> @BusinessObject
> public class SunSet{ @BusinessField private String color="red"; getter/setter }
> and then compare any instance of ColouredCat with a Sunset instance, finding out that the redColouredCat is (for my business logic) equal to a default instance of a Sunset. And also more tricky cases are handled (different BusinessFields, no BusinessObject annotation and so on).
> We intensively use Hibernate and the utility demonstrated to work fine with CGLIB proxies
> We always thought about the possibility to create a new Open Source project but then it was decided it would be better adding the feature to an already well know open source project...
> If you are interested I can send you more details. How can we (me more one other developer) eventually became committers?
> Thanks in advance,
> Vicio.
> P.s.: an utility method to automatically populate the BusinessFields of a BusinessObject is also implemented.
> P.s.2: In the meanwhile I started creating a new OpenSource project here: http://code.google.com/p/simplestuff/ 

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