java - 未调用 HttpSessionBindingListner 方法

Question

我正在尝试 HttpSessionBindingListener 示例，但事件未触发。我在这里做错了什么。

这是我尝试设置的 Attribute 类的代码和 servlet 类的代码。

servlet 正在工作，但没有显示我期望的输出。

    public class SimpleAttribute implements HttpSessionBindingListener {

        PrintWriter writer;

        public  SimpleAttribute(PrintWriter writer) {
            this.writer = writer;
        }

        public void valueBound(HttpSessionBindingEvent event) {
            writer.write("Value bound called");
            writer.write("<br/>");
        }

        public void valueUnbound(HttpSessionBindingEvent event) {
            writer.write("value Unbound called");
            writer.write("<br/>");


}
}




public class SessionBindingServlet extends HttpServlet {

    private static final String SIMPLEATTR = "simpleattribute";

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws IOException {

        ServletContext servletContext = getServletContext();            
        PrintWriter out = response.getWriter();
        response.setContentType("text/html");
        try {
            servletContext.removeAttribute(SIMPLEATTR);
            out.write("removed previous attribute successfully");
            out.write("<br/>");
        } catch (Exception e) {

        }

        servletContext.setAttribute(SIMPLEATTR, new SimpleAttribute(out));
        out.write("Added simple attribute successfully");
        out.write("<br/>");
    }
}

Answer 1

您实际上并未将对象绑定(bind)到 HttpSession，而是将其绑定(bind)到 ServletContext。

您应该使用

检索HttpSession

HttpSession session = request.getSession(true);

并添加属性

session.setAttribute(SIMPLEATTR, new SimpleAttribute(out));

这将触发一个HttpSessionBindingEvent，它将通知您的HttpSessionBindingListener实现类对象。