JavaWeb 两个疑问解答-转发和重定向显示的问题+前端转后端乱码问题-2023-04-06
一、转发和重定向显示的问题
如果想在index.jsp中输入表单内容，提交后的 username 和 password 信息通过转发在另一个页面显示。
只能用requestDispatcher, 不能用sendredirect
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录界面</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/login" method="post">
<span>用户名:</span> <input type="text" name="username" > <br>
<span>密码:</span> <input type="text" name="password" > <br>
爱好：<br>
<input type="checkbox" name="hobbys" value="足球">足球
<input type="checkbox" name="hobbys" value="basketball">篮球
<input type="checkbox" name="hobbys" value="排球">排球
<br>
<input type="submit">
</form>
</body>
</html>package com.feijian.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Arrays;
public class RequestServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
String username = req.getParameter("username");
String password = req.getParameter("password");
System.out.println(username+" : "+password);
String[] hobbys = req.getParameterValues("hobbys");
System.out.println(Arrays.toString(hobbys));
for (String hobby : hobbys) {
resp.getWriter().println(hobby);
}
// resp.sendRedirect("/r/success.jsp");
// req.setAttribute("msg",username);
// req.setAttribute("msg1",password);
req.setAttribute("msg",username);
req.setAttribute("msg1",password);
req.getRequestDispatcher("/success.jsp").forward(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}<?xml version="1.0" encoding="UTF-8"?>
<web-app 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_4_0.xsd"
version="4.0">
<servlet>
<servlet-name>request</servlet-name>
<servlet-class>com.feijian.servlet.RequestServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>request</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>为什么不能用SendRedirect 是因为重定向会跳转到第二个页面，系统认为是第二个request, 显然第一个request的信息不会传给第二个response,相当于两个独立的request 和 response
在从前端多个爱好选项内容，写入后端在控制台上显示乱码问题。主要是在Tomcat上要做虚拟机的代码说明，如下：
