基于SpringMVC的基础文件上传与下载

springmvc配置文件

<!--    bean扫描-->
    <context:component-scan base-package="uploadfile.comtroller"></context:component-scan>

<!--    Thymeleaf视图解析器-->
    <bean id="thymeleafViewResolver" class="org.thymeleaf.spring6.view.ThymeleafViewResolver">
        <property name="characterEncoding" value="UTF-8"></property>
        <property name="order" value="1"></property>
        <property name="templateEngine">
         <bean id="thymeleafViewResolver" class="org.thymeleaf.spring6.SpringTemplateEngine">
        <property name="templateResolver">
            <bean class="org.thymeleaf.spring6.templateresolver.SpringResourceTemplateResolver">
            <!--设置模板文件的位置（前缀）-->
            <property name="prefix" value="/WEB-INF/templates/"/>
            <!--设置模板文件后缀（后缀），Thymeleaf文件扩展名不一定是html，也可以是其他，例如txt，大部分都是html-->
            <property name="suffix" value=".html"/>
            <!--设置模板类型，例如：HTML,TEXT,JAVASCRIPT,CSS等-->
            <property name="templateMode" value="HTML"/>
            <!--用于模板文件在读取和解析过程中采用的编码字符集-->
            <property name="characterEncoding" value="UTF-8"/>
            </bean>
        </property>
     </bean>
        </property>
    </bean>
<!--    注解驱动-->
    <mvc:annotation-driven/>
<!--指定了当用户访问根路径("/")时，将会返回名为"index"的视图-->
    <mvc:view-controller path="/" view-name="index"></mvc:view-controller>

web.xml配置

<servlet>
    <servlet-name>springmvc</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:springmvc-servlet.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
    <multipart-config>
        <!--设置单个支持最大文件的大小-->
        <max-file-size>2097152</max-file-size>
        <!--设置整个表单所有文件上传的最大值-->
        <max-request-size>2097152</max-request-size>
        <!--设置最小上传文件大小-->
        <file-size-threshold>0</file-size-threshold>
    </multipart-config>

</servlet>
<servlet-mapping>
    <servlet-name>springmvc</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

前端简单实现

文件上传表单 enctype设置请求头的内容类型
enctype="application/x-www-form-urlencoded" 是默认类型
enctype="multipart/form-data" 文件上传
@{/file/up} 是一个Thymeleaf的URL表达式
type="file" 固定设置

<form th:action="@{/file/up}" method="post" enctype="multipart/form-data">
    文件上传：<input type="file" name="fileName"/><br>
    <input type="submit" value="上传">
</form>

<a th:href="@{/download}">文件下载</a>

后端实现

@RequestMapping(value = "/file/up",method = RequestMethod.POST)
public String uploadFile(@RequestParam("fileName") MultipartFile multipartFile, HttpServletRequest request) throws IOException {
    //获取上传的文件名
    String originalFilename = multipartFile.getOriginalFilename();
    BufferedInputStream bin = new BufferedInputStream(multipartFile.getInputStream());
    String uploadPath = request.getServletContext().getRealPath("upload");
    File file = new File(uploadPath);
    if(!file.exists()){
        file.mkdirs();//创建文件夹
    }
    //使用UUID避免同名文件 上传覆盖
   String destFile = uploadPath + "/" + UUID.randomUUID().toString()+  originalFilename.substring(originalFilename.lastIndexOf("."));
    //写出  到服务器
    BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(destFile,true));
    //边读边写
    byte [] bytes = new byte[1024*1024];
    int count = 0;
    while ((count = bin.read(bytes))!=-1){
        bos.write(bytes,0,count);
    }
    bos.flush();
    bos.close();
    bin.close();
    return "OK";
}

@GetMapping("/download")
public ResponseEntity<byte []> downloadFile(HttpServletRequest request) throws IOException {
    File file = new File(request.getServletContext().getRealPath("/upload") + "/1.jpg");
    //设置响应体
    //1.创建响应头
    HttpHeaders httpHeaders = new HttpHeaders();
    //2.设置响应类型
    httpHeaders.setContentType(MediaType.APPLICATION_OCTET_STREAM);
    //3.设置下载文件名   file.getName()  1.jpg   attachment附件
    httpHeaders.setContentDispositionFormData("attachment",file.getName());
    //下载文件    file.toPath() 文件的绝对路径  
   return new ResponseEntity<byte []>(Files.readAllBytes(file.toPath()),httpHeaders, HttpStatus.OK);
}