Generating Proper equals() and hashCode() by @Equiv Annotations

We've released a small Groovy library named "kobo-commons" which has some convenience features for Groovy programming.

• http://github.com/kobo/kobo-commons

@Equiv annotation is one of the features.

If you annotate fields by @Equiv annotations, you can dynamically generate
proper equals() and hashCode() using specified fields.


If you wrote the following groovy code:

class Sample {
    @Equiv
    String name

    @Equiv
    String value

    String ignored
}

then you could use equals method and hashCode method:

def s1 = new Sample(name:'John', value:'Good', ignored:'Garbage')
def s2 = new Sample(name:'John', value:'Good', ignored:'Gold')
def s3 = new Sample(name:'John', value:'Bad',  ignored:'Garbage')
def s4 = new Sample(name:'Mike', value:'Good', ignored:'Garbage')
    
assert s1 == s1
assert s1 == s2
assert s1 != s3
assert s1 != s4
    
assert s1.hashCode() == s1.hashCode()
assert s1.hashCode() == s2.hashCode()
assert s1.hashCode() != s3.hashCode()
assert s1.hashCode() != s4.hashCode()

I think it's useful for entities, etc. You can keep your classes very simple.