SPringboot 断言机制

最新推荐文章于 2025-03-23 18:30:00 发布

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本文介绍了SpringBoot中的断言机制，包括自定义异常查找和描述方法，重点讲解了`BeanInCycle`类在处理循环依赖问题中的应用。同时，展示了如何通过`LoggingFailureAnalysisReporter`报告和分析启动失败情况。

1.SpringBoot 断言机制：

	@SuppressWarnings("unchecked")
	private <C extends Exception> C findMostNestedCause(Throwable root, Class<C> type) {
		Throwable candidate = root;
		C result = null;
		while (candidate != null) {
			if (type.isAssignableFrom(candidate.getClass())) {
				result = (C) candidate;
			}
			candidate = candidate.getCause();
		}
		return result;
	}

private String getDescription(BeanInstantiationException ex) {
		if (ex.getConstructingMethod() != null) {
			return String.format("Method %s in %s", ex.getConstructingMethod().getName(),
					ex.getConstructingMethod().getDeclaringClass().getName());
		}
		if (ex.getConstructor() != null) {
			return String.format("Constructor in %s",
					ClassUtils.getUserClass(ex.getConstructor().getDeclaringClass()).getName());
		}
		return ex.getBeanClass().getName();
	}

private static final class BeanInCycle {

		private final String name;

		private final String description;

		private BeanInCycle(BeanCreationException ex) {
			this.name = ex.getBeanName();
			this.description = determineDescription(ex);
		}

		private String determineDescription(BeanCreationException ex) {
			if (StringUtils.hasText(ex.getResourceDescription())) {
				return String.format(" defined in %s", ex.getResourceDescription());
			}
			InjectionPoint failedInjectionPoint = findFailedInjectionPoint(ex);
			if (failedInjectionPoint != null && failedInjectionPoint.getField() != null) {
				return String.format(" (field %s)", failedInjectionPoint.getField());
			}
			return "";
		}

		private InjectionPoint findFailedInjectionPoint(BeanCreationException ex) {
			if (ex instanceof UnsatisfiedDependencyException unsatisfiedDependencyException) {
				return unsatisfiedDependencyException.getInjectionPoint();
			}
			return null;
		}

		@Override
		public boolean equals(Object obj) {
			if (this == obj) {
				return true;
			}
			if (obj == null || getClass() != obj.getClass()) {
				return false;
			}
			return this.name.equals(((BeanInCycle) obj).name);
		}

		@Override
		public int hashCode() {
			return this.name.hashCode();
		}

		@Override
		public String toString() {
			return this.name + this.description;
		}

		static BeanInCycle get(Throwable ex) {
			if (ex instanceof BeanCreationException beanCreationException) {
				return get(beanCreationException);
			}
			return null;
		}

		private static BeanInCycle get(BeanCreationException ex) {
			if (StringUtils.hasText(ex.getBeanName())) {
				return new BeanInCycle(ex);
			}
			return null;
		}

	}

}

public final class LoggingFailureAnalysisReporter implements FailureAnalysisReporter {

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

	@Override
	public void report(FailureAnalysis failureAnalysis) {
		if (logger.isDebugEnabled()) {
			logger.debug("Application failed to start due to an exception", failureAnalysis.getCause());
		}
		if (logger.isErrorEnabled()) {
			logger.error(buildMessage(failureAnalysis));
		}
	}

	private String buildMessage(FailureAnalysis failureAnalysis) {
		StringBuilder builder = new StringBuilder();
		builder.append(String.format("%n%n"));
		builder.append(String.format("***************************%n"));
		builder.append(String.format("APPLICATION FAILED TO START%n"));
		builder.append(String.format("***************************%n%n"));
		builder.append(String.format("Description:%n%n"));
		builder.append(String.format("%s%n", failureAnalysis.getDescription()));
		if (StringUtils.hasText(failureAnalysis.getAction())) {
			builder.append(String.format("%nAction:%n%n"));
			builder.append(String.format("%s%n", failureAnalysis.getAction()));
		}
		return builder.toString();
	}

}