private ConcurrentHashMap<String, Locker> relation = new ConcurrentHashMap<String, Locker>();

protected void doGet(HttpServletRequest request, final HttpServletResponse response) {

    final String id = request.getParameter("id");

    if(null != id){

        final Locker locker = relation.get(id);   //此处的效率？

        if(locker == null){

            Locker lock = new Locker(id, false);

            synchronized(lock){

                try{

                    relation.put(id, lock);

                    System.out.println(id + "开始等待，relation.size() = " + relation.size());

                    lock.wait(5000l); //设置超时时间

                    HttpClientUtil.httpGetRequest("http://localhost:8080/Test/BusiServlet?id=" + 2);

                    System.out.println(id + "同步处理完成，relation.size() = " + relation.size());

                }catch(InterruptedException e){

                    e.printStackTrace();

                }

            }

            try{

                response.serHeader("content-type", "text/html;charset=utf-8");

                if(relation.containsKey(id)){

                    response.getOutputStream().write(("失败...." + id).getBytes("utf-8"));

                } else {

                    response.getOutputStream().write(("成功...." + id).getBytes("utf-8"));

                }

            }catch(IOException e){

                e.printStackTrace();

            }

        } else {

            //此处需要加锁？

            synchronized(locker){

                try{

                    locker.notify();

                }catch(Exception e){

                    e.printStackTrace();

                }

                relation.remove(id);

            }

        }

    }

}

class Locker{

    String id;

    boolean dir;

    //Getter and Setter

}