I have a new approach to write a reflection-equals utility that will likely
execute noticeably faster than the current approach. It will also let us add
new strategies, such as an EqualsBuilder to use method properties, as requested
in issue LANG-332. It will also allow us to add whatever other new strategies
developers may propose.
A class that uses my new approach to determine equality and return hash codes
might look something like this:
public class Widget implements Comparable<Widget> { // Fields,
properties, and methods go here private static final
Reflector<Widget> reflector = Reflector.buildPropertyReflector(Widget.class)
.includeTransientProperties(trPropertyName1, trPropertyName2)
.exclude(propertyName1) .build();
@Override public boolean equals(Object other) { return
reflector.doEquals(this, other); } @Override public int
hashCode() { return reflector.doHashCode(this); } }
There are three main advantages to doing it this way:
1. By creating the reflector class at class-load time, we speed up the process
of comparing the instances. With the current EqualsBuilder class, much of the
work to implement equals() gets duplicated each time it gets called.
2. It simplifies the user's task of writing the equals method. The user no
longer needs to start each equals() method like this:
public boolean equals(Object obj) { if (obj == null) { return false; }
if (obj == this) { return true; } if (obj.getClass() !=
getClass()) { return false; } ... }
Instead, all this work will be done in the call to reflector.doEquals(this,
other)
3. The approach will make it easier to add new strategies. The example above
calls the buildPropertyReflector() method. Other methods may be written to
implement other approaches. For example, another strategy could be added that
would also generate a compareTo() method, to implement the Comparable
implementation that's consistent with equals() and hashCode(). This would
probably involve annotations that can be used to specify the comparison order
of the various fields or properties.
I've written a class like this before, so I know it works, and I know the
pitfalls. In short, I would like you to assign the LANG-332 task to me.
-- Miguel Muñoz
