ConfigurationWarningsApplicationContextInitializer Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/context/ConfigurationWarningsApplicationContextInitializer.java lines 53–216

public class ConfigurationWarningsApplicationContextInitializer
		implements ApplicationContextInitializer<ConfigurableApplicationContext> {

	private static final Log logger = LogFactory.getLog(ConfigurationWarningsApplicationContextInitializer.class);

	@Override
	public void initialize(ConfigurableApplicationContext context) {
		context.addBeanFactoryPostProcessor(new ConfigurationWarningsPostProcessor(getChecks()));
	}

	/**
	 * Returns the checks that should be applied.
	 * @return the checks to apply
	 */
	protected Check[] getChecks() {
		return new Check[] { new ComponentScanPackageCheck() };
	}

	/**
	 * {@link BeanDefinitionRegistryPostProcessor} to report warnings.
	 */
	protected static final class ConfigurationWarningsPostProcessor
			implements PriorityOrdered, BeanDefinitionRegistryPostProcessor {

		private final Check[] checks;

		public ConfigurationWarningsPostProcessor(Check[] checks) {
			this.checks = checks;
		}

		@Override
		public int getOrder() {
			return Ordered.LOWEST_PRECEDENCE - 1;
		}

		@Override
		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		}

		@Override
		public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
			for (Check check : this.checks) {
				String message = check.getWarning(registry);
				if (StringUtils.hasLength(message)) {
					warn(message);
				}
			}

		}

		private void warn(String message) {
			if (logger.isWarnEnabled()) {
				logger.warn(String.format("%n%n** WARNING ** : %s%n%n", message));
			}
		}

	}

	/**
	 * A single check that can be applied.
	 */
	@FunctionalInterface
	protected interface Check {

		/**
		 * Returns a warning if the check fails or {@code null} if there are no problems.
		 * @param registry the {@link BeanDefinitionRegistry}
		 * @return a warning message or {@code null}
		 */
		@Nullable String getWarning(BeanDefinitionRegistry registry);

	}

	/**
	 * {@link Check} for {@code @ComponentScan} on problematic package.
	 */
	protected static class ComponentScanPackageCheck implements Check {

		private static final Set<String> PROBLEM_PACKAGES;

		static {
			Set<String> packages = new HashSet<>();
			packages.add("org.springframework");
			packages.add("org");
			PROBLEM_PACKAGES = Collections.unmodifiableSet(packages);
		}

		@Override
		public @Nullable String getWarning(BeanDefinitionRegistry registry) {
			Set<String> scannedPackages = getComponentScanningPackages(registry);
			List<String> problematicPackages = getProblematicPackages(scannedPackages);
			if (problematicPackages.isEmpty()) {
				return null;
			}
			return "Your ApplicationContext is unlikely to start due to a @ComponentScan of "
					+ StringUtils.collectionToDelimitedString(problematicPackages, ", ") + ".";
		}

		protected Set<String> getComponentScanningPackages(BeanDefinitionRegistry registry) {
			Set<String> packages = new LinkedHashSet<>();
			String[] names = registry.getBeanDefinitionNames();
			for (String name : names) {
				BeanDefinition definition = registry.getBeanDefinition(name);
				if (definition instanceof AnnotatedBeanDefinition annotatedDefinition) {
					addComponentScanningPackages(packages, annotatedDefinition.getMetadata());
				}
			}
			return packages;
		}

		private void addComponentScanningPackages(Set<String> packages, AnnotationMetadata metadata) {
			AnnotationAttributes attributes = AnnotationAttributes
				.fromMap(metadata.getAnnotationAttributes(ComponentScan.class.getName(), true));
			if (attributes != null) {
				addPackages(packages, attributes.getStringArray("value"));
				addPackages(packages, attributes.getStringArray("basePackages"));
				addClasses(packages, attributes.getStringArray("basePackageClasses"));
				if (packages.isEmpty()) {
					packages.add(ClassUtils.getPackageName(metadata.getClassName()));
				}
			}
		}

		private void addPackages(Set<String> packages, String @Nullable [] values) {
			if (values != null) {
				Collections.addAll(packages, values);
			}
		}

		private void addClasses(Set<String> packages, String @Nullable [] values) {
			if (values != null) {
				for (String value : values) {
					packages.add(ClassUtils.getPackageName(value));
				}
			}
		}

		private List<String> getProblematicPackages(Set<String> scannedPackages) {
			List<String> problematicPackages = new ArrayList<>();
			for (String scannedPackage : scannedPackages) {
				if (isProblematicPackage(scannedPackage)) {
					problematicPackages.add(getDisplayName(scannedPackage));
				}
			}
			return problematicPackages;
		}

		private boolean isProblematicPackage(@Nullable String scannedPackage) {
			if (scannedPackage == null || scannedPackage.isEmpty()) {
				return true;
			}
			return PROBLEM_PACKAGES.contains(scannedPackage);
		}

		private String getDisplayName(@Nullable String scannedPackage) {
			if (scannedPackage == null || scannedPackage.isEmpty()) {
				return "the default package";
			}
			return "'" + scannedPackage + "'";
		}

	}

}