Package groovy.transform

Annotation Type NullCheck

@Documented
@Retention(SOURCE)
@Target({TYPE,METHOD,CONSTRUCTOR})
public @interface NullCheck

Class, method or constructor annotation which indicates that each parameter should be checked to ensure it isn't null. If placed at the class level, all explicit methods and constructors will be checked. Explicit means those declared within the class and not inherited or added by transforms (but see includeGenerated()).

Example usage:

 import groovy.transform.NullCheck
 import static groovy.test.GroovyAssert.shouldFail

 @NullCheck
 class Greeter {
     private String audience

     Greeter(String audience) {
         this.audience = audience.toLowerCase()
     }

     String greeting(String salutation) {
         salutation.toUpperCase() + ' ' + audience
     }
 }

 assert new Greeter('World').greeting('hello') == 'HELLO world'

 def ex = shouldFail(IllegalArgumentException) { new Greeter(null) }
 assert ex.message == 'audience cannot be null'

 ex = shouldFail(IllegalArgumentException) { new Greeter('Universe').greeting(null) }
 assert ex.message == 'salutation cannot be null'
 

The produced code for the above example looks like this:

 class Greeter {
     private String audience

     Foo(String audience) {
         if (audience == null) throw new IllegalArgumentException('audience cannot be null')
         this.audience = audience.toLowerCase()
     }

     String greeting(String salutation) {
         if (salutation == null) throw new IllegalArgumentException('salutation cannot be null')
         salutation.toUpperCase() + ' ' + audience
     }
 }
 

Since:

3.0.0

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element	Description
boolean	includeGenerated	Whether to try to add null checking to generated methods/constructors such as those added by other transforms.

Element Details

includeGenerated

boolean includeGenerated

Whether to try to add null checking to generated methods/constructors such as those added by other transforms. Using this option may lead to surprising results, e.g. it will only apply to methods/constructors added prior to when the NullCheck transformation is processed. Null checking is not enabled for constructors containing generated bytecode or generated constructors with calls to this(...) or super(...) regardless of this flag.

Since:

3.0.2

Default:

false