@Delegate was introduced as feature in lombok v0.10. It was moved to the experimental package in lombok v1.14; the old version from the main lombok package is now deprecated.
Experimental because:
@Delegate
generate delegates for whatever you didn't manually implement, but due to issues with generics erasure this also can't be made to work without caveats.
Any field or no-argument method can be annotated with @Delegate
to let lombok generate delegate methods that forward the call to this field (or the result of invoking this method).
Lombok delegates all public
methods of the field's type (or method's return type), as well as those of its supertypes except for all
methods declared in java.lang.Object
.
You can pass any number of classes into the @Delegate
annotation's types
parameter.
If you do that, then lombok will delegate all public
methods in those types (and their supertypes, except java.lang.Object
) instead of looking at the field/method's type.
All public non-Object
methods that are part of the calculated type(s) are copied, whether or not you also wrote implementations for those methods. That would thus result in duplicate method errors. You can avoid these
by using the @Delegate(excludes=SomeType.class)
parameter to exclude all public methods in the excluded type(s), and their supertypes.
To have very precise control over what is delegated and what isn't, write private inner interfaces with method signatures, then specify these
private inner interfaces as types in @Delegate(types=PrivateInnerInterfaceWithIncludesList.class, excludes=SameForExcludes.class)
.
lombok.delegate.flagUsage
= [warning
| error
] (default: not set)@Delegate
as a warning or error if configured.
When passing classes to the annotation's types
or excludes
parameter, you cannot include generics.
This is a limitation of java. Use private inner interfaces or classes that extend the intended type including the
generics parameter to work around this problem.
When passing classes to the annotation, these classes do not need to be supertypes of the field. See the example.
@Delegate
cannot be used on static fields or methods.
@Delegate
cannot be used when the calculated type(s) to delegate / exclude themselves contain @Delegate
annotations; in other words, @Delegate
will error if you attempt to use it recursively.