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The data in servlet is transferred to JSP page, and the problem cannot be displayed using El expression ${}

2022-07-03 02:16:00 【Grilled little fat sheep with charcoal...】

Problem description ： el expression ${} The data of the tag is not displayed on the page .

First look at my servlet and jsp page .

Servlet Code :

@WebServlet(urlPatterns = "/demo1")
public class Servlet extends HttpServlet {
    
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        // 1.  Prepare the data 
        List<Brand> brands = new ArrayList<>();
        brands.add(new Brand(1," The three little squirrels "," The three little squirrels ",100," The three little squirrels , It's delicious but not hot ",1));
        brands.add(new Brand(2," uniqlo "," uniqlo ",200," uniqlo , Suit life ",0));
        brands.add(new Brand(3," millet "," Xiaomi Technology Co., Ltd ",1000," Born with a fever ",1));

        // 2.  Store in request domain 
        request.setAttribute("brands", brands);

        // 3.  Forwarding to  el-demo.jsp in 
        request.getRequestDispatcher("/el-demo.jsp").forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        this.doGet(request, response);
    }
}

JSP Code ：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    ${brands}
</body>
</html>

Access in a browser ：http://localhost:8080/Jsp_demo/demo1, Discover the use of setAttribute Packaged in brands The data in the field is not displayed

Insert picture description here
reason ：JSP and Servlet Version results in el The function is off by default , Join in <%@page isELIgnored="false"%> Label manual opening el function .

After modification JSP Code ：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page isELIgnored="false"%>   <%--   Add this tag to start it manually el function   --%>
<html>
<head>
    <title>Title</title>
</head>
<body>
    ${brands}
</body>
</html>

Access... Again in the browser ：http://localhost:8080/Jsp_demo/demo1, el expression ${} It's normal to show .
Insert picture description here

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