根据java.lang.NoClassDefFoundError: org.slf4j.LoggerFactory错误信息可以轻松的知道，错误的原因是因为缺少slf4j日志组件jar包造成的，slf4j是一个开源的日志组件，和log4j类似，都是用来记录日志的开源组件。
问题信息：
2015-1-31 21:28:14 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [activiti.cfg.xml]
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'processEngineConfiguration' defined in class path resource [activiti.cfg.xml]: Instantiation of bean failed; nested exception is java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:946)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:890)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:479)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:450)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:290)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:287)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:189)
at org.activiti.engine.impl.cfg.BeansConfigurationHelper.parseProcessEngineConfiguration(BeansConfigurationHelper.java:36)
at org.activiti.engine.impl.cfg.BeansConfigurationHelper.parseProcessEngineConfigurationFromResource(BeansConfigurationHelper.java:48)
at org.activiti.engine.ProcessEngineConfiguration.createProcessEngineConfigurationFromResource(ProcessEngineConfiguration.java:185)
at org.activiti.engine.ProcessEngineConfiguration.createProcessEngineConfigurationFromResourceDefault(ProcessEngineConfiguration.java:177)
at com.bug315.ActivitiTest01.main(ActivitiTest01.java:10)
Caused by: java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
at org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl.<clinit>(ProcessEngineConfigurationImpl.java:219)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:126)
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:72)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:938)
... 12 more
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
... 20 more
解决办法：
将slf4j-api-1.6.0.jar、slf4j-simple-1.6.0.jar两个jar包导入到当前项目的classpath下面即可解决（下载地址：https://www.slf4j.org/download.html）。
