java.lang.NoClassDefFoundError

异常原因

其实就是和Java虚拟机的工作原理有关了，下面简单介绍一下JVM的类加载机制

类加载器三个机制：委托、单一性、可见性
委托：指加载一个类的请求交给父类加载器，若父类加载器不可以找到或者加载到，再加载这个类
单一性：指子类加载器不会再次加载父类加载器已经加载过的类
可见性：子类加载器可以看见父类加载器加载的所有类，而父类加载器不可以看到子类加载器加载的类

JVM的类加载机制的委托行机制，决定了类加载器只加载一次，子类加载器不会再加载父类加载器已经加载过的类。
所有在一些特定条件下就会出现编译时可以加载到类，运行时不可以加载到类，这时候就会出现java.lang.NoClassDefFoundError异常。
此类错误一般出现在自动注入的操作中，因此常出现在Spring框架里。

目前有发现几种情况:
1、一种情况就是因为静态变量加载不到原因;
2、工程里没有将jar添加到classpath，maven项目的，需要根据项目情况排查.

解决方案

一般情况下，如果确认了该类确实存在，我们都会rebuild或者clean一下工程，让项目重新编译一遍。
如果该类在工程中不存在，则需要将该类引用进工程中。

举例

堆栈信息

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'systemStatusService' defined in URL [jar:file:/D:/.m2/repository/com/epoint/frame/epoint-common/9.3.3-sp1/epoint-common-9.3.3-sp1.jar!/com/epoint/basic/api/systemstatus/SystemStatusService.class]: Initialization of bean failed; nested exception is java.lang.NoClassDefFoundError: org/aspectj/util/PartialOrder$PartialComparable
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:547)
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
   at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303)
   at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
   at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
   at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
   at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
   at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:762)
   at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
   at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:664)
   at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:630)
   at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:678)
   at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:549)
   at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:490)
   at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
   at javax.servlet.GenericServlet.init(GenericServlet.java:160)
   at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1280)
   at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1193)
   at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1088)
   at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5176)
   at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5460)
   at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
   at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
   at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
   at java.util.concurrent.FutureTask.run(FutureTask.java:266)
   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
   at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NoClassDefFoundError: org/aspectj/util/PartialOrder$PartialComparable
   at java.lang.ClassLoader.defineClass1(ClassLoader.java)
   at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
   at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
   at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
   at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
   at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
   at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
   at java.security.AccessController.doPrivileged(Native Method)
   at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
   at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1191)
   at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1669)
   at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1547)
   at org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator.sortAdvisors(AspectJAwareAdvisorAutoProxyCreator.java:73)
   at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.findEligibleAdvisors(AbstractAdvisorAutoProxyCreator.java:91)
   at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.getAdvicesAndAdvisorsForBean(AbstractAdvisorAutoProxyCreator.java:69)
   at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.wrapIfNecessary(AbstractAutoProxyCreator.java:330)
   at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessAfterInitialization(AbstractAutoProxyCreator.java:293)
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:422)
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1577)
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539)
   ... 27 more
Caused by: java.lang.ClassNotFoundException: org.aspectj.util.PartialOrder$PartialComparable
   at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1702)
   at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1547)
   ... 47 more

分析

重点提示为：

Error creating bean with name 'systemStatusService' defined in URL [jar:file:/D:/.m2/repository/com/epoint/frame/epoint-common/9.3.3-sp1/epoint-common-9.3.3-sp1.jar!/com/epoint/basic/api/systemstatus/SystemStatusService.class]: Initialization of bean failed; nested exception is java.lang.NoClassDefFoundError: org/aspectj/util/PartialOrder$PartialComparable

经排查，工程未引用org.aspectj.util.PartialOrder类所在jar包——aspectjweaver-1.8.9.jar。