Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/httpclient/HttpConnectionManager
at test.ExchangeMail.init(ExchangeMail.java:40)
at test.ExchangeMail.main(ExchangeMail.java:129)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.httpclient.HttpConnectionManager
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)
... 2 more
求助怎么解决呀