了解SpringMVC的上传和下载

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
    https://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context
    https://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/aop
    https://www.springframework.org/schema/aop/spring-aop.xsd
    http://www.springframework.org/schema/tx
    https://www.springframework.org/schema/tx/spring-tx.xsd
    http://www.springframework.org/schema/mvc
    https://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!--    开启ioc注解开启扫描-->
    <context:component-scan base-package="cn.hp"></context:component-scan>
    <!--    开启mvc的注解扫描  里面有个转换服务器-->
    <mvc:annotation-driven ></mvc:annotation-driven>
    <!--    将视图解析器 交给spring-->
    <bean id="resolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <!--        <property name="prefix" value="/WEB-INF/pages/"></property>-->
        <property name="prefix" value="/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

    <!--    配置一个bean 让他支持文件上传-->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!--        俩属性 name="defaultEncoding" 编码格式utf-8
                    name="maxUploadSize" 文件上传最大 值 100M
        -->
        <property name="defaultEncoding" value="utf-8"></property>
        <property name="maxUploadSize" value="10240000"></property>
    </bean>
</beans>

<?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>dispatcherServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!-- 初始化时加载springmvc配置文件 -->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:*.xml</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcherServlet</servlet-name>
        <url-pattern>*.do</url-pattern>
    </servlet-mapping>
    <filter>
        <filter-name>fileEncoding</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>Encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>fileEncoding</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

package cn.hp.controller;
import org.apache.commons.io.FileUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Date;
import java.util.Random;
@Controller
public class FileUploadController {
    @RequestMapping(value="upload.do")
    public String upload(MultipartFile file[], HttpServletRequest request) throws IOException {
        //1.获取上传文件路径
        String path = request.getServletContext().getRealPath("/upload");
        for (int i =0;i<file.length;i++) {
            //2.拿到上传的文件名
            String name = file[i].getOriginalFilename();
            //3.改名，把用户上传的文件进行改名操作
            String newNmae = new Date().getTime() + new Random().nextInt(999999) + name;
            //4.实例化File类的对象加载上传的路径和文件
            File f = new File(path + newNmae);
            //5. MultipartFile里面的方法把这个路径的文件写入过去
            file[i].transferTo(f);
        }
        return "success";
    }
    @RequestMapping(value="download.do")
    public ResponseEntity<byte[]> download(@RequestParam("fileName") String fileName,HttpServletRequest request) throws IOException {
        //1.下载路径
        String path = request.getServletContext().getRealPath("/download/");
        //2.实例化File类的对象加载下载的路径和文件
        File f= new File(path+fileName);
        //3.转格式
        String newName = new String(fileName.getBytes("utf-8"),"iso8859-1");
        //4.转流
        HttpHeaders hh = new HttpHeaders();
        hh.setContentDispositionFormData("attachment",newName);
        hh.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        //5.相应发送
        return  new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(f),hh, HttpStatus.CREATED);
    }
}

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<%--如果说表单有文件上传的功能，那么表达就要设置这个属性--%>
<form action="upload" method="post" enctype="multipart/form-data">
    文件上传<input type="file" name="file" /><br/>
    文件上传<input type="file" name="file" /><br/>
    文件上传<input type="file" name="file" /><br/>
    <input type="submit" value="确定" />
</form>
<a href="download/自我介绍模板.docx">下载文件</a>
<a href="download/10.png">下载文件</a>
<a href="download/4.jpg">下载文件1</a>
<a href="download.do?fileName=新建文本文档.txt">下载文件2</a>
<a href="download/新建文本文档.txt">下载文件3</a>
</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
上传成功
</body>
</html>