freeMarker取数据取不出来

Question

   我用ftl模板取后台数据,取不出来,打开浏览器运行 http://localhost:9090/f01 就跟我下载一个f01的不知道是什么文件,还有时就是原样输出

java代码:

package com.freemarker.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/f01")
public class FreeMarker01 extends HttpServlet {

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置数据(给模板设置数据)
        req.setAttribute("msg","Hello FreeMarker!!!");
        //请求转发跳转到指定的模板页面: template/f01.ftl
        req.getRequestDispatcher("template/f01.ftl").forward(req,resp);
    }
}

web.xml:

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>

  <servlet>
    <servlet-name>freemarker</servlet-name>
    <servlet-class>freemarker.ext.servlet.FreemarkerServlet</servlet-class>
    <init-param>
      <!--模板路径-->
      <param-name>Templatepath</param-name>
      <!--默认在webapp目录下查找对应的模板文件-->
      <param-value>/</param-value>
    </init-param>
    
    <init-param>
      <!--模板默认的编码UTF-8-->
      <param-name>default_encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </servlet>

  <!--处理所有以.ftl结尾的文件,ftl是freemarker默认的文件后缀-->
  <servlet-mapping>
    <servlet-name>freemarker</servlet-name>
    <url-pattern>.ftl</url-pattern>
  </servlet-mapping>
</web-app>

f01.ftl 就只有一句输出

${msg}  

Answer 1

resp.setAttribute("msg","Hello FreeMarker!!!");

为什么要用重定向？