ERROR Failed to load driver

log4j:ERROR Failed to load driver
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver 
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:338)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at org.apache.log4j.jdbc.JDBCAppender.setDriver(JDBCAppender.java:391)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.log4j.config.PropertySetter.setProperty(PropertySetter.java:245)
	at org.apache.log4j.config.PropertySetter.setProperty(PropertySetter.java:204)
	at org.apache.log4j.config.PropertySetter.setProperties(PropertySetter.java:169)
	at org.apache.log4j.config.PropertySetter.setProperties(PropertySetter.java:104)
	at org.apache.log4j.PropertyConfigurator.parseAppender(PropertyConfigurator.java:842)
	at org.apache.log4j.PropertyConfigurator.parseCategory(PropertyConfigurator.java:768)
	at org.apache.log4j.PropertyConfigurator.configureRootCategory(PropertyConfigurator.java:648)
	at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:514)
	at org.apache.log4j.PropertyConfigurator.doConfigure(PropertyConfigurator.java:580)
	at org.apache.log4j.helpers.OptionConverter.selectAndConfigure(OptionConverter.java:526)
	at org.apache.log4j.LogManager.<clinit>(LogManager.java:127)
	at org.apache.log4j.Logger.getLogger(Logger.java:117)
	at top.simba1949.AppTest.<clinit>(AppTest.java:11)

解决方案：

将log4j.properties 中每行后面的空格都删除就解决了.