在网上查阅的相关代码，基本都一样，试过都报这个错，请高手指点 
代码： 
public   static   void   toXML(Object   bean)   { 
FileOutputStream   xmlData   =   null; 
JOXBeanOutputStream   joxOut   =   null; 
try   { 
xmlData   =   new   FileOutputStream( "d:/bean.xml "); 
        joxOut   =   new   JOXBeanOutputStream(xmlData, "UTF-8 ");//这句报错 
joxOut.writeObject( "person ",   bean); 
}   catch   (Exception   exc)   { 
exc.printStackTrace(); 
}   finally   { 
try   { 
xmlData.close(); 
joxOut.close(); 
}   catch   (Exception   e)   { 
e.printStackTrace(); 
} 
} 
} 


错误信息： 
java.lang.NullPointerException 
at   com.jox.main.JoxMain.toXML(JoxMain.java:56) 
at   com.jox.main.JoxMain.main(JoxMain.java:79) 
Exception   in   thread   "main "   java.lang.NoClassDefFoundError:   org/apache/xml/serialize/OutputFormat 
at   com.wutka.jox.JOXBeanOutputStream.setupSink(JOXBeanOutputStream.java:173) 
at   com.wutka.jox.JOXBeanOutputStream. <init> (JOXBeanOutputStream.java:82) 
at   com.jox.main.JoxMain.toXML(JoxMain.java:49) 
at   com.jox.main.JoxMain.main(JoxMain.java:79) 
Caused   by:   java.lang.ClassNotFoundException:   org.apache.xml.serialize.OutputFormat 
at   java.net.URLClassLoader$1.run(URLClassLoader.java:200) 
at   java.security.AccessController.doPrivileged(Native   Method) 
at   java.net.URLClassLoader.findClass(URLClassLoader.java:188) 
at   java.lang.ClassLoader.loadClass(ClassLoader.java:307) 
at   sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) 
at   java.lang.ClassLoader.loadClass(ClassLoader.java:252) 
at   java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) 
...   4   more

jar包打了，代码是不报错的，运行报错