The Holy Java

Building the right thing, building it right, fast

Groovy: Use @Canonical to Get Compiler-generated Equals, HashCode and ToString

Posted by Jakub Holý on November 2, 2011

Groovy makes it extremely easy to create Java beans with getters, setters, equals, hashCode, and toString:

@groovy.transform.Canonical
class Call {
   def method
   def args

   /* // custom impl. reusing the auto-generated one:
   String toString() {
      _toString().replaceFirst("^.*?Call", "")
   }*/
}

You can then do:

// Auto-gen. constr. with positional arguments:
def call1 = new Call("someMethod", "someArgs")
def call2 = new Call(method: "someMethod", args: "someArgs")
assert call1.getMethod() == call1.method
assert call2.equals(call1)
assert ([call1, call2] as Set).size() == 1 // hashCode

As you might have noticed, you may provide your own implementation of toString and reuse the auto-generated toString by calling _toString().

References

JavaDoc for @Canonical. You can also use separately any of: @ToString. @EqualsAndHashCode, @TupleConstructor. And may be check also the other available AST annotations such as Immutable and Synchronized and perhaps also groovy.beans‘s Bindable and Vetoable annotations, if you need true Java Beans.

About these ads

One Response to “Groovy: Use @Canonical to Get Compiler-generated Equals, HashCode and ToString”

  1. […] Groovy: Use @Canonical to Get Compiler-generated Equals, HashCode and ToString […]

Sorry, the comment form is closed at this time.

 
%d bloggers like this: