@Data

Overview

@Data is a convenient shortcut annotation that bundles the features of @ToString, @EqualsAndHashCode and @Getter / @Setter together: In other words, @Data generates all the boilerplate that is normally associated with simple POJOs (Plain Old Java Objects) and beans: getters for all fields, setters for all non-final fields, and appropriate toString, equals and hashCode implementations that involve the fields of the class. In addition, @Data generates a constructor that initializes all final fields, as well as all non-final fields with no initializer that have been marked with @NonNull or @NotNull, in order to ensure the field is never null.

@Data is like having implicit @ToString and @EqualsAndHashCode annotations on the class. However, the parameters of @ToString and @EqualsAndHashCode (such as callSuper, includeFieldNames and exclude) cannot be set with @Data. If you need to set non-default values for any of these parameters, just add those annotations explicitly; @Data is smart enough to defer to those annotations.

All generated getters and setters will be public. To override the access level, annotate the field with an explicit @Setter and/or @Getter annotation. You can also use this annotation (by combining it with AccessLevel.NONE) to suppress generating a getter and/or setter altogether.

All fields marked as transient will not be considered for hashCode and equals. All static fields will be skipped entirely (not considered for any of the generated methods, and no setter/getter will be made for them).

If the class already contains a method with the same name as any method that would normally be generated, that method is not generated, and no warning or error is emitted. For example, if you already have a method with signature void hashCode(int a, int b, int c), no int hashCode() method will be generated, even though technically int hashCode() is an entirely different method. The same rule applies to the constructor, toString, equals, and all getters and setters.

@Data can handle generics parameters for fields just fine. In order to reduce the boilerplate when constructing objects for classes with generics, you can use the staticConstructor parameter to generate a private constructor, as well as a static method that returns a new instance. This way, javac will infer the variable name. Thus, by declaring like so: @Data(staticConstructor="of") class Foo<T> { private T x;} you can create new instances of Foo by writing: Foo.of(5); instead of having to write: new Foo<Integer>(5);.

Small print