请教：关于 Applet ,servlet,JNI的问题

applet与servlet通信，让后在servlet中使用本地代码，即 JNI，出现错误，调试了好久，还是出错，请各位大侠指教！谢谢！ 代码如下：applet端：import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;/**
 * Simple demonstration for an Applet <-> Servlet communication.
 */
public class RobotApplet extends Applet {
private TextField inputField = new TextField();
private TextField outputField = new TextField();
private TextArea exceptionArea = new TextArea(); /**
 * Setup the GUI.
 */
public void init() {
// set new layout
setLayout(new GridBagLayout()); // add title
Label title = new Label("监控界面", Label.CENTER);
title.setFont(new Font("SansSerif", Font.BOLD, 14));
GridBagConstraints c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;
c.weightx = 1.0;
c.fill = GridBagConstraints.HORIZONTAL;
c.insets = new Insets(5, 5, 5, 5);
add(title, c); // add input label, field and send button
c = new GridBagConstraints();
c.anchor = GridBagConstraints.EAST;
add(new Label("距离: ", Label.RIGHT), c);
c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 1.0;
add(inputField, c);
Button sendButton = new Button("Forward");
c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;
add(sendButton, c);
sendButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
onSendData();
}
}); // add output label and non-editable field
c = new GridBagConstraints();
c.anchor = GridBagConstraints.EAST;
add(new Label("反馈结果: ", Label.RIGHT), c);
c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 50.0;
add(outputField, c);
outputField.setEditable(false); // add exception label and non-editable textarea
c = new GridBagConstraints();
c.anchor = GridBagConstraints.EAST;
add(new Label("异常结果: ", Label.RIGHT), c);
c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;
c.weighty = 1;
c.fill = GridBagConstraints.BOTH;
add(exceptionArea, c);
exceptionArea.setEditable(false);
} /**
 * Get a connection to the servlet.
 */
private URLConnection getServletConnection()
throws MalformedURLException, IOException { // Connection zum Servlet 鰂fnen
URL urlServlet = new URL(getCodeBase(), "echo");
URLConnection con = urlServlet.openConnection(); // konfigurieren
con.setDoInput(true);
con.setDoOutput(true);
con.setUseCaches(false);
con.setRequestProperty(
"Content-Type",
"application/x-java-serialized-object"); // und zur點kliefern
return con;
} /**
 * Send the inputField data to the servlet and show the result in the outputField.
 */
private void onSendData() {
try {
// get input data for sending
String input = inputField.getText(); // send data to the servlet
URLConnection con = getServletConnection();
OutputStream outstream = con.getOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(outstream);
oos.writeObject(input);
oos.flush();
oos.close(); // receive result from servlet
InputStream instr = con.getInputStream();
ObjectInputStream inputFromServlet = new ObjectInputStream(instr);
String result = (String) inputFromServlet.readObject();
inputFromServlet.close();
instr.close(); // show result
outputField.setText(result); } catch (Exception ex) {
ex.printStackTrace();
exceptionArea.setText(ex.toString());
}
}
}
servlet 端：import java.io.*;
import java.io.IOException;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
//import java.lang.Math;public class KongZhiServlet extends HttpServlet
{   static{
    System.loadLibrary("control");
}
   public native boolean SKConnect(); 
  public void service(HttpServletRequest request,HttpServletResponse     response)throws ServletException, IOException 
{
try 
{
response.setContentType("application/x-java-serialized-object"); InputStream in = request.getInputStream();
ObjectInputStream inputFromApplet = new ObjectInputStream(in);
         String echo = (String) inputFromApplet.readObject();

OutputStream outstr = response.getOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(outstr);  

boolConnect = this.SKConnect(); if (boolConnect)
{
   oos.writeObject("nihao");
}

oos.flush();
oos.close(); } 
catch (Exception e) 
{
    e.printStackTrace();
}
}

}这段代码的本意就是由applet发送一个简单的字符给 servlet,然后再servlet中调用本地的函数实现一些功能，然后再返回数据之类的给 applet.如果不加上 本地代码即 static{
    System.loadLibrary("control");
}
这段，applet 和 servlet之间是可以互相通信的，加上后就会出现异常，
java.io.IOException: Server returned HTTP response code: 500 for URL: http://localhost:8088/echo/echo另外我用的是 Tomcat ,将本地代码生成的 .Dll 文件放在了C:\Program Files\Apache Software Foundation\Tomcat 4.1\webapps\echo\WEB-INF\classes 下面请各位指教，谢谢!!!