session - 当绑定(bind)/未绑定(bind)到 HTTP session 时获取通知

Question

当我的对象绑定(bind)/未绑定(bind)到 HTTP session 对象时，我如何收到通知。

Answer 1

让对象的类实现 HttpSessionBindingListener .

public class YourObject implements HttpSessionBindingListener {

    @Override
    public void valueBound(HttpSessionBindingEvent event) {
        // The current instance has been bound to the HttpSession.
    }

    @Override
    public void valueUnbound(HttpSessionBindingEvent event) {
        // The current instance has been unbound from the HttpSession.
    }

}

如果您无法控制对象的类代码，因此无法更改其代码，则另一种方法是实现 HttpSessionAttributeListener .

@WebListener
public class YourObjectSessionAttributeListener implements HttpSessionAttributeListener {

    @Override
    public void attributeAdded(HttpSessionBindingEvent event) {
        if (event.getValue() instanceof YourObject) {
            // An instance of YourObject has been bound to the session.
        }
    }

    @Override
    public void attributeRemoved(HttpSessionBindingEvent event) {
        if (event.getValue() instanceof YourObject) {
            // An instance of YourObject has been unbound from the session.
        }
    }

    @Override
    public void attributeReplaced(HttpSessionBindingEvent event) {
        if (event.getValue() instanceof YourObject) {
            // An instance of YourObject has been replaced in the session.
        }
    }

}

注意:当您仍在使用 Servlet 2.5 或更早版本时，请替换 @WebListener通过<listener> web.xml中的配置条目.