Question

我遇到了简单的Java表单提交问题。

我有我的login.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>The best login page in the world</title>
    </head>
    <body>

        <h1>Connexion</h1>
        <form id="asdasd" name="coucou" method="post" action="doLogin">
            <input type="text" name="user_email" />
            <input type="password" name="user_password" />
            <input type="submit" name="asd" value="Se connecter" />

        </form>
    </body>
</html>

我的web.xml指定doLogin in fact the servlet loginServlet

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
    <context-param>
        <param-name>javax.faces.PROJECT_STAGE</param-name>
        <param-value>Development</param-value>
    </context-param>
    <servlet>
        <servlet-name>Faces Servlet</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet>
        <servlet-name>loginServlet</servlet-name>
        <servlet-class>com.courses.web.servlet.loginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>/faces/*</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>loginServlet</servlet-name>
        <url-pattern>/loginServlet</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>loginServlet</servlet-name>
        <url-pattern>/doLogin</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
    <welcome-file-list>
        <welcome-file>faces/index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

我的loginServlet.java

public class loginServlet extends HttpServlet {


    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        try (PrintWriter out = response.getWriter()) {

        }
    }

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

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse response) {
        String username = req.getParameter("user_email");
        String password = req.getParameter("user_password");

        Console console = System.console();
        console.printf("mail : %s\npassword: %s\n", username,password);

    }

    @Override
    public String getServletInfo() {
        return "Short description";
    }

}

没有什么比这更复杂，但是我从getParameter得到的变量总是为NULL，我不知道为什么。

我做错了什么？

Answer 1

由于您尚未发布堆栈跟踪，因此唯一可以返回null值的行就是这一行：

Console console = System.console();

你的评论注意到：我在Netbeans中运行glassfish 。所以，这一行将抛出NullPointerException：

console.printf("mail : %s\npassword: %s\n", username,password); //console is null

尝试使用记录器来打印消息。只是为了一个简单的快速解决方案，请使用System.out.println，直到您碰巧配置和使用记录器。所以，简而言之，替换这些行：

Console console = System.console();
console.printf("mail : %s\npassword: %s\n", username,password);

要：

System.out.printf("mail : %s\npassword: %s\n", username,password));

JSP中的Java post表单，servlet中的get参数返回NULL

1 个答案: