DefaultBootstrapContext Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/bootstrap/DefaultBootstrapContext.java lines 38–143

public class DefaultBootstrapContext implements ConfigurableBootstrapContext {

	private final Map<Class<?>, InstanceSupplier<?>> instanceSuppliers = new HashMap<>();

	private final Map<Class<?>, Object> instances = new HashMap<>();

	private final ApplicationEventMulticaster events = new SimpleApplicationEventMulticaster();

	@Override
	public <T> void register(Class<T> type, InstanceSupplier<T> instanceSupplier) {
		register(type, instanceSupplier, true);
	}

	@Override
	public <T> void registerIfAbsent(Class<T> type, InstanceSupplier<T> instanceSupplier) {
		register(type, instanceSupplier, false);
	}

	private <T> void register(Class<T> type, InstanceSupplier<T> instanceSupplier, boolean replaceExisting) {
		Assert.notNull(type, "'type' must not be null");
		Assert.notNull(instanceSupplier, "'instanceSupplier' must not be null");
		synchronized (this.instanceSuppliers) {
			boolean alreadyRegistered = this.instanceSuppliers.containsKey(type);
			if (replaceExisting || !alreadyRegistered) {
				Assert.state(!this.instances.containsKey(type), () -> type.getName() + " has already been created");
				this.instanceSuppliers.put(type, instanceSupplier);
			}
		}
	}

	@Override
	public <T> boolean isRegistered(Class<T> type) {
		synchronized (this.instanceSuppliers) {
			return this.instanceSuppliers.containsKey(type);
		}
	}

	@Override
	@SuppressWarnings("unchecked")
	public <T> @Nullable InstanceSupplier<T> getRegisteredInstanceSupplier(Class<T> type) {
		synchronized (this.instanceSuppliers) {
			return (InstanceSupplier<T>) this.instanceSuppliers.get(type);
		}
	}

	@Override
	public void addCloseListener(ApplicationListener<BootstrapContextClosedEvent> listener) {
		this.events.addApplicationListener(listener);
	}

	@Override
	public <T> @Nullable T get(Class<T> type) throws IllegalStateException {
		return getOrElseThrow(type, () -> new IllegalStateException(type.getName() + " has not been registered"));
	}

	@Override
	public <T> @Nullable T getOrElse(Class<T> type, @Nullable T other) {
		Supplier<@Nullable T> supplier = () -> other;
		return getOrElseSupply(type, supplier);
	}

	@Override
	public <T> @Nullable T getOrElseSupply(Class<T> type, Supplier<@Nullable T> other) {
		synchronized (this.instanceSuppliers) {
			InstanceSupplier<?> instanceSupplier = this.instanceSuppliers.get(type);
			return (instanceSupplier != null) ? getInstance(type, instanceSupplier) : other.get();
		}
	}

	@Override
	public <T, X extends Throwable> @Nullable T getOrElseThrow(Class<T> type, Supplier<? extends X> exceptionSupplier)
			throws X {
		synchronized (this.instanceSuppliers) {
			InstanceSupplier<?> instanceSupplier = this.instanceSuppliers.get(type);
			if (instanceSupplier == null) {
				throw exceptionSupplier.get();
			}
			return getInstance(type, instanceSupplier);
		}
	}

	@SuppressWarnings("unchecked")
	private <T> @Nullable T getInstance(Class<T> type, InstanceSupplier<?> instanceSupplier) {
		T instance = (T) this.instances.get(type);
		if (instance == null) {
			instance = (T) instanceSupplier.get(this);
			if (instance == null) {
				return null;
			}
			if (instanceSupplier.getScope() == Scope.SINGLETON) {
				this.instances.put(type, instance);
			}
		}
		return instance;
	}

	/**
	 * Method to be called when {@link BootstrapContext} is closed and the
	 * {@link ApplicationContext} is prepared.
	 * @param applicationContext the prepared context
	 */
	public void close(ConfigurableApplicationContext applicationContext) {
		this.events.multicastEvent(new BootstrapContextClosedEvent(this, applicationContext));
	}

}