Servlet可以有多步交互吗？

Question

Is there any way to start executing java Servlet code (specifically, in Websphere Application Server) (one session, one thread on the Servlet) and then pause to get more information from the calling client at various points? I require that the current session, and ongoing Servlet thread, not die until specified, and instead keep waiting (open) for information from the client.

Is this kind of ongoing conversation possible? Or can the Servlet call to "doPost" only be started - and then the Servlet ignores the client until it finishes?

Answer 1

As suggested, I would use an object stored in session to maintain the state needed. You can also modify the session on a servlet by servlet basis if you need certain actions to extend the session timeout beyond the webapp defaults using the following method in the HttpSession API:

public void setMaxInactiveInterval(int interval) Specifies the time, in seconds, between client requests before the servlet container will invalidate this session. A negative time indicates the session should never timeout.

You just need to establish your logic for your object setting/retrieval from session. Typically something like this:

HttpSession session = req.getSession();
MyBeanClass bean;
Object temp = null;

temp = session.getAttribute("myBean");
if(temp !=null) {
    bean = (MyBeanClass) temp;
} else {
    bean = new MyBeanClass();
}

// Logic

session.setAttribute("myBean", bean);

Answer 2

I have not done this with directly, but the underlying support is somewhat related to Jetty's continuation model and Servlet 3.0 Suspend/Resume support .

Web frameworks that work like the post description (actually, they are resumed across different connections) are sometimes called Continuation-Based frameworks . I am unsure of any such frameworks in Java (as the Java language is not conducive to such models) but there are two rather well known examples of the general principle:

1. Seaside (for Smalltalk) and;
2. Lift (for Scala).

Hope this was somewhat useful.

Answer 3

您可以保存/更新请求之间的会话状态，当下一个请求到来时，您可以还原并继续执行您的操作。