我是java spring的新手，想通过教程学习它。在教程中，我收到以下错误：此错误也出现在另一个项目中……出了什么问题？
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.<init>(DefaultSingletonBeanRegistry.java:81)
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.<init>(FactoryBeanRegistrySupport.java:43)
at org.springframework.beans.factory.support.AbstractBeanFactory.<init>(AbstractBeanFactory.java:176)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.<init>(AbstractAutowireCapableBeanFactory.java:159)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.<init>(AbstractAutowireCapableBeanFactory.java:170)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.<init>(DefaultListableBeanFactory.java:165)
at org.springframework.beans.factory.xml.XmlBeanFactory.<init>(XmlBeanFactory.java:78)
at org.springframework.beans.factory.xml.XmlBeanFactory.<init>(XmlBeanFactory.java:67)
at org.semiz.DrawingApp.main(DrawingApp.java:12)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory
at java.net.URLClassLoader$1.run(Unknown Source)
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)
... 9 more
这是课程：
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.FileSystemResource;
public class DrawingApp {
public static void main(String[] args) {
BeanFactory factory = new XmlBeanFactory(new FileSystemResource(
"spring.xml"));
Triangle triangle = (Triangle) factory.getBean("triangle");
triangle.draw();
}
}
public class Triangle {
public void draw() {
System.out.println("Triangle draw");
}
}