java.lang.NoClassDefFoundError: org/springframework/boot/context/annotation/ImportCandidates

报错：

java.lang.NoClassDefFoundError: org/springframework/boot/context/annotation/ImportCandidates
	at org.springframework.boot.autoconfigure.AutoConfigurationImportSelector.getCandidateConfigurations(AutoConfigurationImportSelector.java:184) ~[spring-boot-autoconfigure-2.7.5.jar:2.7.5]
	at org.springframework.boot.autoconfigure.AutoConfigurationImportSelector.getAutoConfigurationEntry(AutoConfigurationImportSelector.java:125) ~[spring-boot-autoconfigure-2.7.5.jar:2.7.5]
	at org.springframework.boot.autoconfigure.AutoConfigurationImportSelector$AutoConfigurationGroup.process(AutoConfigurationImportSelector.java:440) ~[spring-boot-autoconfigure-2.7.5.jar:2.7.5]
	at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorGrouping.getImports(ConfigurationClassParser.java:879) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorGroupingHandler.processGroupImports(ConfigurationClassParser.java:809) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorHandler.process(ConfigurationClassParser.java:780) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:193) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:331) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:247) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:311) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:112) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:746) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:564) ~[spring-context-5.3.16.jar:5.3.16]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.5.10.jar:2.5.10]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) [spring-boot-2.5.10.jar:2.5.10]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:448) [spring-boot-2.5.10.jar:2.5.10]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:339) [spring-boot-2.5.10.jar:2.5.10]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1365) [spring-boot-2.5.10.jar:2.5.10]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1354) [spring-boot-2.5.10.jar:2.5.10]
	at com.order.service.OrderApplication.main(OrderApplication.java:16) [classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_333]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_333]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_333]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_333]
	at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.5.10.jar:2.5.10]
Caused by: java.lang.ClassNotFoundException: org.springframework.boot.context.annotation.ImportCandidates
	at java.net.URLClassLoader.findClass(URLClassLoader.java:387) ~[na:1.8.0_333]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:418) ~[na:1.8.0_333]
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:355) ~[na:1.8.0_333]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:351) ~[na:1.8.0_333]
	... 25 common frames omitted


进程已结束,退出代码0

出现了 Application run failed 的错误提示，表明应用启动失败了。

具体的错误根源是 java.lang.NoClassDefFoundError: org/springframework/boot/context/annotation/ImportCandidates

org.springframework.boot.autoconfigure.AutoConfigurationImportSelector 类的 getCandidateConfigurations 方法中

这个方法我前面写了自动配置原理，是获取自动配置相关的候选配置类，找不到这个类

查看 Caused by 部分，发现是 java.lang.ClassNotFoundException: org.springframework.boot.context.annotation.ImportCandidates，

也就是确实在类加载过程中，按照当前的类路径找不到这个具体的类，这大概率是项目依赖的 Spring Boot 相关 JAR 包版本不一致或者依赖缺失等情造成的。

从项目使用的 Spring Boot 相关依赖版本来看，有个依赖是自动导入的，没有进入底面的配置约束，所以存在 spring-boot-autoconfigure-2.7.5.jar


结论就是：存在 spring-boot-autoconfigure-2.7.5.jar 等不同版本混用的情况（启动类所在的 Spring Boot 版本是 2.5.10，导致部分配置相关的自动配置类找不到）

解决办法，交给上层 pom 管理 移除版本号