java.lang.NoClassDefFoundError: javax/mail/internet/AddressException解決

初學log4j，用于監聽系統運作狀态，因為系統要一直運作，是以用了發送郵件通知功能，結果報錯了，如下： Exception in thread "Animation Thread" java.lang.NoClassDefFoundError: javax/mail/internet/AddressException at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Unknown Source) at java.lang.Class.getConstructor0(Unknown Source) at java.lang.Class.newInstance0(Unknown Source) at java.lang.Class.newInstance(Unknown Source) at org.apache.log4j.helpers.OptionConverter.instantiateByClassName(OptionConverter.java:336) at org.apache.log4j.helpers.OptionConverter.instantiateByKey(OptionConverter.java:123) at org.apache.log4j.PropertyConfigurator.parseAppender(PropertyConfigurator.java:752) at org.apache.log4j.PropertyConfigurator.parseCategory(PropertyConfigurator.java:735) at org.apache.log4j.PropertyConfigurator.parseCatsAndRenderers(PropertyConfigurator.java:639) at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:504) at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:395) at org.apache.log4j.PropertyConfigurator.configure(PropertyConfigurator.java:403) at source.MapDistribution.setup(MapDistribution.java:84) at processing.core.PApplet.handleDraw(Unknown Source) at processing.core.PApplet.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Caused by: java.lang.ClassNotFoundException: javax.mail.internet.AddressException 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) ... 17 more 傻傻的找了很多資料，嘗試了未果。後來想起來以前做的一個項目也用到mail功能，當時好像導入了一個庫的。在現在項目裡找了半天，GOD！居然沒有！去下了javamail，把庫導入到項目裡，OK，解決！ 折騰了半天，原來是這種小錯誤，嗚呼哀哉……