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

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

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().


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.

Published by Jakub Holý

I’m a JVM-based developer since 2005, consultant, and occasionally a project manager, working currently with Iterate AS in Norway.

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