为什么在尝试读取.DOCX文件时出现异常？

尝试.docx使用以下代码段读取文件时：

public void parseDocxFile(String textEntered) {
    try {
        XWPFDocument doc = new XWPFDocument(new FileInputStream(new File(SContainer.getFilePath())));
        XWPFWordExtractor extractor = new XWPFWordExtractor(doc);
        System.out.println("DOCX File : " + extractor.getText());
    }catch(Exception exc) {exc.printStackTrace();}
}

我遇到一个异常，它说：

Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: org/apache
/xmlbeans/XmlException
at org.suhail.gui.Main.parseDocxFile(Main.java:246)
at org.suhail.gui.Main.jButton1ActionPerformed(Main.java:167)
at org.suhail.gui.Main.access$000(Main.java:22)
at org.suhail.gui.Main$1.actionPerformed(Main.java:71)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
at java.awt.Component.processMouseEvent(Component.java:6038)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3260)
at java.awt.Component.processEvent(Component.java:5803)
at java.awt.Container.processEvent(Container.java:2058)
at java.awt.Component.dispatchEventImpl(Component.java:4410)
at java.awt.Container.dispatchEventImpl(Container.java:2116)
at java.awt.Component.dispatchEvent(Component.java:4240)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
at java.awt.Container.dispatchEventImpl(Container.java:2102)
at java.awt.Window.dispatchEventImpl(Window.java:2429)
at java.awt.Component.dispatchEvent(Component.java:4240)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

这是什么意思 ？为什么会发生？