java阻止在我的应用程序中多次访问servlet

Question

下面给出了配置为autosys作业的url。这将调用下面给出的servlet。有谁能建议我如何保护这个方法“psServiceWrapper.processHRFeed（）；”每次连续按此url（比如10次）时，通过不正确的数据修改不断调用此url。我希望一次只能访问一个线程

我知道我必须使用同步方法或块。。我不知道该怎么做。。因为我对线程不太熟悉

http://mydomain:11000/dorf/HRDORFScriptServlet?script=hrFeed


public class HRDORFScriptServlet extends HttpServlet {

private static final long serialVersionUID = 1L;
private static final Logger log = Logger.getLogger(HRDORFScriptServlet.class);
private final String script = "script";

@Override
protected void doGet(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
    // TODO Auto-generated method stub
    performTask(arg0, arg1);
}

@Override
protected void doPost(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
    // TODO Auto-generated method stub
    performTask(arg0, arg1);
}

 /** Execute the servlet.
 * 
 * @param request
 * @param response
 * @throws ServletException
 * @throws IOException
 */
public void performTask(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException {

    DorfUser dorfUser = DorfSessionUtils.getDorfUser(request.getSession());
    HRDorfFeedServiceWrapper psServiceWrapper = new HRDorfFeedServiceWrapper(dorfUser);
    String reqParam = request.getParameter(script);
    if(reqParam.equals("hrFeed")){
    try{
        psServiceWrapper.processHRFeed();           
    }
    catch(ServiceException se){
        log.error("Error While calling HRFeed Service : "+se.getMessage());
    }
    catch(Exception e){
        log.error("Error While calling HRFeed Service : "+e.getMessage());
    }

    }
 }

}

Answer 1

synchronized(this){ 
 psServiceWrapper.processHRFeed();     
}

但这将导致瓶颈，因为servlet将在当前线程执行psServiceWrapper.processHRFeed();之前停止响应

如果您使用的是Java5，也可以使用ReetrantLock

A reentrant mutual exclusion Lock with the same basic behavior and semantics as the implicit monitor lock accessed using synchronized methods and statements, but with extended capabilities.

   private final ReentrantLock lock = new ReentrantLock();//Declare it

像下面那样使用它

 lock.lock();  // block until condition holds
 try {
   psServiceWrapper.processHRFeed();
 } finally {
   lock.unlock()
 }

Answer 2

我将把psServiceWrapper.processHRFeed()的功能移到一个实现Runnable的简单类

public class MyTask implements Runnable
{
    public void run() 
    {
        psServiceWrapper.processHRFeed();
    }
}

然后创建一个固定线程池大小为1的ExecutorService

ExecutorService psServiceRunner = Executors.newFixedThreadPool(1);

每次调用servlet时，我都会将MyTask的一个实例发布到这个servlet

psServiceRunner.execute(new MyTask());

这将

1. 不要阻止servlet调用程序
2. 确保在任何时间点只有一个servlet可以运行该方法