在Servlet和JSP中如何实现多线程安全？

import javax.servlet.http.HttpServlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
//该类模拟多线程Servlet的情况
public class SmulateMultiThread implements Runnable{
  public SmulateMultiThread() {
  }
  public static void main(String[] args) {
   //处理100个请求
    for(int i=0;i<100;i++)
    {
      new Thread(new SmulateMultiThread()).start();
    }
  }
  public void run()  {
    HttpServletRequest request=null;
    HttpServletResponse  response=null;
    try {
      WebContainer.getServlet().doGet(request, response);
    }
    catch (IOException ex) {
    }
    catch (ServletException ex) {
    }
  }
}
//这是一个Servlet类
class UnsafeServlet extends HttpServlet{
  private String unsafe;
  public void init() throws ServletException {
  }
  //Process the HTTP Get request
  public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
    unsafe=Thread.currentThread().getName();
    System.out.println(unsafe);
  }
}
//这个是容器类
class WebContainer{
  private static UnsafeServlet us=new UnsafeServlet();
  public static UnsafeServlet getServlet(){
    return us;
  }
}

<%! String unsafeVar; %> //不是线程安全的
<% String safeVar; %>      // 线程安全的