JSTL 和 Servlet 中的单选按钮

Question

我在 JSP 文件中有一些值，将单选按钮推送到 Servlet 并输出它时出现问题。

输入文件在这个jsp:

<label for="phone">Phone: </label>
    <input type="text" name="phone" id="phone" value="${phone}"><br/><br/>

    <input type="radio" name="sex" id="sex" value="${male}">Male
    <input type="radio" name="sex" id="sex" value="${female}"/>Female<br/><br/>

Servler 在这里：public static RequestNewEmployee fromRequestParameters(HttpServletRequest request) { return new RequestNewEmployee( request.getParameter("firstName"), request.getParameter("lastName"), request.getParameter("email"), request.getParameter("phone"), request.getParameter("sex")); } public void setAsRequestAttributes(HttpServletRequest request) { request.setAttribute("firstName", firstName); request.setAttribute("lastName", lastName); request.setAttribute("email", email); request.setAttribute("phone", phone); request.setAttribute("sex", sex); }

但是，我在性领域没有收到任何 praramentr（尽管所有其他人都正常工作）。可能是什么问题？

Answer 1

理论
${} 称为 EL 表达式。在里面你可以有变量。来自 the oracle tutorial:

The web container evaluates a variable that appears in an expression by looking up its value according to the behavior of PageContext.findAttribute(String). For example, when evaluating the expression ${product}, the container will look for product in the page, request, session, and application scopes and will return its value. If product is not found, null is returned. A variable that matches one of the implicit objects described in Implicit Objects will return that implicit object instead of the variable's value.

现在让我们谈谈您的问题。

您不能有两个具有相同 ID 的 html 标签。
您收到空参数，因为显然它是空的（未定义）。您在哪里定义 male 和 female 变量？

我认为这就是您要实现的目标：

form.jsp

<%@ page contentType="text/html;charset=UTF-8" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <form action="/formServlet">
        <input type="radio" name="sex" id="sexChoice1" value="male">Male
        <input type="radio" name="sex" id="sexChoice2" value="female"/>Female<br/><br/>
        <input type="submit" value="submit">
    </form>
</body>
</html>

FormServlet

public class FormServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
        System.out.println(req.getParameter("sex"));
    }
}

web.xml

<web-app xmlns="http://java.sun.com/xml/ns/javaee" version="2.5">
    <servlet>
        <servlet-name>FormServlet</servlet-name>
        <servlet-class>com.artmal.controller.FormServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>FormServlet</servlet-name>
        <url-pattern>/formServlet</url-pattern>
    </servlet-mapping>
</web-app>

选择 'male' 选项并提交后的控制台输出：

male

JSTL 和 Servlet 中的单选按钮

Radio button in JSTL and Servlet

jsp

servlets

el