问题弹出式显示(Java 1.4)

只需让servlet将条件存储在请求范围内,让jsp有条件地打印javascript代码。

Servlet:

boolean exist = yourDAO.exist(parameters);
request.setAttribute("exist", exist);
request.getRequestDispatcher("page.jsp").forward(request, response);

JSP(使用JSTL):

<c:if test="${!exist}">
    <script>
        if (confirm('Data does not exist, do you want to continue?')) {
            // Do whatever you want when user want to continue ("goes on screen").
        } else {
            // Do whatever you want when user don't want to continue ("returns to starting point").
        }
    </script>
</c:if>

我会按照以下步骤做一些事情:

首先,在进行数据库检查时设置一个布尔标志

<%
    boolean POPUP_FLAG = /*condition check*/
%>

然后,如果您的渲染代码是这样的,您可以检查标记并在页面中包含一个window.open(视情况而定)。

<%
  if (POPUP_FLAG) {
%>
    <script>
    window.open("popup.jsp", "_blank");
    </script>
    /*
      Include here any special details to display on the main page in popup mode
    */
<%
  } else {
%>
    /*
      Include here the normal information you would want displayed when not in popup mode
    */
<%
  }
%>