刚刚开始学习Spring，于是在eclipse下引入了spring的包，等一切配置完成后，开始运行，没有想到报错，如下所示：
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory
at org.springframework.context.support.AbstractApplicationContext.<init>(AbstractApplicationContext.java:145)
at org.springframework.context.support.AbstractRefreshableApplicationContext.<init>(AbstractRefreshableApplicationContext.java:84)
at org.springframework.context.support.AbstractRefreshableConfigApplicationContext.<init>(AbstractRefreshableConfigApplicationContext.java:59)
at org.springframework.context.support.AbstractXmlApplicationContext.<init>(AbstractXmlApplicationContext.java:58)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:136)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:93)
at org.nupt.springtest.A.main(A.java:10)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
… 7 more
仔细得看了看错误，发现缺少一个类：org/apache/commons/logging/LogFactory。
于是开始Google，发现，只要引入logging.jar这个包，问题就可以解决。
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