Java 从servlet向html页面发送警报
我正在尝试使用Javaservlet创建一个注册页面。如何在html页面上通知表单中的空字段?这是我代码的一部分Java 从servlet向html页面发送警报,java,servlets,Java,Servlets,我正在尝试使用Javaservlet创建一个注册页面。如何在html页面上通知表单中的空字段?这是我代码的一部分 String uName = request.getParameter("username"); String pass = request.getParameter("passwd"); String rpass = request.getParameter("rpasswd"); String email = request
String uName = request.getParameter("username");
String pass = request.getParameter("passwd");
String rpass = request.getParameter("rpasswd");
String email = request.getParameter("email");
if(uName == "" || pass == "" || rpass == "" || email == "") {
//what must i put here to send notification to html page
}
您可以使用&,例如:
String uName = request.getParameter("username");
String pass = request.getParameter("passwd");
String rpass = request.getParameter("rpasswd");
String email = request.getParameter("email");
if(uName == null|| pass == null || rpass == null || email == null) {
//here you can set attribute like any error message
request.setAttribute("error", "Please fill all fields in form");
request.getRequestDispatcher("yourjsppage").forward(request,response);
}
要显示上面的消息
,请在jsp页面中执行以下操作:
//this line will print whatever is in error : Please fill all fields in form
<p class="text-center" style="color: green">${error}</p>
您可以使用&,例如:
String uName = request.getParameter("username");
String pass = request.getParameter("passwd");
String rpass = request.getParameter("rpasswd");
String email = request.getParameter("email");
if(uName == null|| pass == null || rpass == null || email == null) {
//here you can set attribute like any error message
request.setAttribute("error", "Please fill all fields in form");
request.getRequestDispatcher("yourjsppage").forward(request,response);
}
要显示上面的消息
,请在jsp页面中执行以下操作:
//this line will print whatever is in error : Please fill all fields in form
<p class="text-center" style="color: green">${error}</p>
然后在jspPage中添加这行代码
<p>${error}</p>
然后在jspPage中添加这行代码
<p>${error}</p>
它不是那样工作的,你需要返回一个新页面。您也可以在提交表单之前进行客户端验证。同意@Oleg。另外,请记住,在检查字符串相等性时使用equals方法,而不是“==”。它不是那样工作的,您需要返回一个新页面。您也可以在提交表单之前进行客户端验证。同意@Oleg。请记住,在检查字符串是否相等而不是“==”时,请使用equals方法。