注释类型 NonNull

@Target({METHOD,PARAMETER,FIELD})
@Retention(RUNTIME)
@Documented
@Nonnull
@TypeQualifierNickname
public @interface NonNull

A common Spring annotation to declare that annotated elements cannot be null.

Leverages JSR-305 meta-annotations to indicate nullability in Java to common tools with JSR-305 support and used by Kotlin to infer nullability of Spring API.

Should be used at parameter, return value, and field level. Method overrides should repeat parent @NonNull annotations unless they behave differently.

Use @NonNullApi (scope = parameters + return values) and/or @NonNullFields (scope = fields) to set the default behavior to non-nullable in order to avoid annotating your whole codebase with @NonNull.