ServletListenerRegistrationBean Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/web/servlet/ServletListenerRegistrationBean.java lines 59–149

public class ServletListenerRegistrationBean<T extends EventListener> extends RegistrationBean {

	private static final Set<Class<?>> SUPPORTED_TYPES;

	static {
		Set<Class<?>> types = new HashSet<>();
		types.add(ServletContextAttributeListener.class);
		types.add(ServletRequestListener.class);
		types.add(ServletRequestAttributeListener.class);
		types.add(HttpSessionAttributeListener.class);
		types.add(HttpSessionIdListener.class);
		types.add(HttpSessionListener.class);
		types.add(ServletContextListener.class);
		SUPPORTED_TYPES = Collections.unmodifiableSet(types);
	}

	private @Nullable T listener;

	/**
	 * Create a new {@link ServletListenerRegistrationBean} instance.
	 */
	public ServletListenerRegistrationBean() {
	}

	/**
	 * Create a new {@link ServletListenerRegistrationBean} instance.
	 * @param listener the listener to register
	 */
	public ServletListenerRegistrationBean(T listener) {
		Assert.notNull(listener, "'listener' must not be null");
		Assert.isTrue(isSupportedType(listener), "'listener' is not of a supported type");
		this.listener = listener;
	}

	/**
	 * Set the listener that will be registered.
	 * @param listener the listener to register
	 */
	public void setListener(T listener) {
		Assert.notNull(listener, "'listener' must not be null");
		Assert.isTrue(isSupportedType(listener), "'listener' is not of a supported type");
		this.listener = listener;
	}

	/**
	 * Return the listener to be registered.
	 * @return the listener to be registered
	 */
	public @Nullable T getListener() {
		return this.listener;
	}

	@Override
	protected String getDescription() {
		Assert.notNull(this.listener, "'listener' must not be null");
		return "listener " + this.listener;
	}

	@Override
	protected void register(String description, ServletContext servletContext) {
		try {
			servletContext.addListener(this.listener);
		}
		catch (RuntimeException ex) {
			throw new IllegalStateException("Failed to add listener '" + this.listener + "' to servlet context", ex);
		}
	}

	/**
	 * Returns {@code true} if the specified listener is one of the supported types.
	 * @param listener the listener to test
	 * @return if the listener is of a supported type
	 */
	public static boolean isSupportedType(EventListener listener) {
		for (Class<?> type : SUPPORTED_TYPES) {
			if (ClassUtils.isAssignableValue(type, listener)) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Return the supported types for this registration.
	 * @return the supported types
	 */
	public static Set<Class<?>> getSupportedTypes() {
		return SUPPORTED_TYPES;
	}

}