jsp调用applet出异常 java.lang.NullPointerException

在java内置applet运行环境中毫无问题，用jsp调用时抛出
java.lang.NullPointerException
at sun.plugin2.applet.Plugin2Manager.findAppletJDKLevel(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
异常：java.lang.NullPointerException
注：应为放到webinf下跑出无法找到指定类所以放到webcontent目录下！代码如下！！！

package applet;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JApplet;
import javax.swing.Timer;

import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.title.TextTitle;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.axis.ValueAxis;
import org.jfree.data.time.*;

/**
* 一个简单的曲线图例子
*
* @author tf date 2007-01-30
*/

public class test extends JApplet {
private static final long serialVersionUID = 3257566209007171634L;

private double cpuValue1=0;
private TimeSeries cpu1=null;

/**
* 内部类--实现动态随机产生虚拟CPU使用率的值
*
* @author