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Servlet和ThreadLocal的测试

时间:2009-12-23 15:42来源:未知 作者:admin 点击:
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public class TestThreadServlet extends HttpServlet { private static ThreadLocal thread = new ThreadLocal(); private int flag = 0; public void doGet( HttpServletRequest request, HttpServletResponse response) throws ServletException, IOExcept

  public class TestThreadServlet extends HttpServlet {
  
  private static ThreadLocal thread    = new ThreadLocal();
  
  private int   flag   = 0;
  
  public void doGet( HttpServletRequest request,
  
   HttpServletResponse response)
  
  throws ServletException, IOException {
  
  flag++;
  
  String str = "This is the first String." + new Object();
  
  if (thread.get() == null)
  
  thread.set(str);
  
  PrintWriter out = response.getWriter();
  
  out.println("<p>");
  
  out.println("<BR>flag : " + flag);
  
  out.println("<BR>sessionid : " + request.getSession().getId());
  
  out.println("<BR>servlet : " + this.toString());
  
  out.println("<BR>thread : " + thread.get());
  
  out.println("</p>");
  
  }
  
  }
  
  执行结果:
  
  Session 1:
  
  flag : 2
  sessionid : amGeaiVwKvL9
  servlet : test.other.TestThreadServlet@5f2db0
  thread : This is the first String.Java.lang.Object@1ad6b4b
  
  Session 1:
  
  flag : 3
  sessionid : aR3GkcUQoXT-
  servlet : test.other.TestThreadServlet@5f2db0
  thread : This is the first String.java.lang.Object@6214f5
  
  由执行结果可以看出
  
  1 服务器对每个Servlet只创建一个实例。flag不停增加
  
  2 Session范围内的ThreadLocal中对象唯一。不同的请求,Object的hashCode相同。
  
  3 不同的Session共享ThreadLocal,但内部对象不同
  
  另:后来有人提醒我,实际上在web.XML为同一个servlet配置不同的名字,将会是两个不同的实例。也就是说,servlet的实例与配置有关。
  
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