InstanceSupplier Type — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/bootstrap/BootstrapRegistry.java lines 99–163

	@FunctionalInterface
	interface InstanceSupplier<T> {

		/**
		 * Factory method used to create the instance when needed.
		 * @param context the {@link BootstrapContext} which may be used to obtain other
		 * bootstrap instances.
		 * @return the instance or {@code null}
		 */
		@Nullable T get(BootstrapContext context);

		/**
		 * Return the scope of the supplied instance.
		 * @return the scope
		 */
		default Scope getScope() {
			return Scope.SINGLETON;
		}

		/**
		 * Return a new {@link InstanceSupplier} with an updated {@link Scope}.
		 * @param scope the new scope
		 * @return a new {@link InstanceSupplier} instance with the new scope
		 */
		default InstanceSupplier<T> withScope(Scope scope) {
			Assert.notNull(scope, "'scope' must not be null");
			InstanceSupplier<T> parent = this;
			return new InstanceSupplier<>() {

				@Override
				public @Nullable T get(BootstrapContext context) {
					return parent.get(context);
				}

				@Override
				public Scope getScope() {
					return scope;
				}

			};
		}

		/**
		 * Factory method that can be used to create an {@link InstanceSupplier} for a
		 * given instance.
		 * @param <T> the instance type
		 * @param instance the instance
		 * @return a new {@link InstanceSupplier}
		 */
		static <T> InstanceSupplier<T> of(@Nullable T instance) {
			return (registry) -> instance;
		}

		/**
		 * Factory method that can be used to create an {@link InstanceSupplier} from a
		 * {@link Supplier}.
		 * @param <T> the instance type
		 * @param supplier the supplier that will provide the instance
		 * @return a new {@link InstanceSupplier}
		 */
		static <T> InstanceSupplier<T> from(@Nullable Supplier<T> supplier) {
			return (registry) -> (supplier != null) ? supplier.get() : null;
		}

	}