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对不起，我提前提出了这个愚蠢的问题，但这个镜头片段无法正常工作。该JSP打印出 “空” 找到下面的代码：getParameter返回null
<html>
<head>
<title></title>
</head>
<body>
<form action="ServletController" method="post">
<input type="text" name="invoice">
<input type="text" name="amount">
<input type="text" name="date">
<input type="submit">
</form>
</body>
</html>
public class ServletController extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setContentType("text/html");
String invoice = req.getParameter("invoice");
String amount = req.getParameter("amount");
String date = req.getParameter("date");
//connection = new DBConn();
//connection.createConnection(invoice, amount, date);
req.setAttribute("attr", invoice);
RequestDispatcher requestDispatcher = req.getRequestDispatcher("index.jsp");
requestDispatcher.forward(req, resp);
}
}
<html>
<head>
<title></title>
</head>
<body>
<%-- String str = (String) request.getParameter("invoice");
PrintWriter writer = response.getWriter();
writer.print(str);
--%>
${param.invoice}
</body>
</html>
<servlet>
<servlet-name>ServContr</servlet-name>
<servlet-class>classes.ServletController</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ServContr</servlet-name>
<url-pattern>/ServletController</url-pattern>
</servlet-mapping>
</servlet>
如果我把scriplet JSP代码返回 “空”，在EL的情况下JSP什么。我试图用HTML表单进行实验，因为我认为浏览器没有正确提出请求的问题，但没有任何结果。请告诉我错误在哪里，为什么$ {}不起作用。谢谢！
小小，感谢您的edditing – aime