16.SpringMVC实现上传下载

SpringMVC为文件上传提供了专门的支持 ， 即插即用的MulitpartResolver

文件上传

1.导入依赖

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.4</version>
</dependency>
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.10.0</version>
</dependency>

2.在spring中进行文件上传的配置

<!--文件上传配置-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!--请求的编码格式，必须和JSP的pageEncoding属性一致，以便于正确读取表单的内容，默认为ISO-8859-1-->
    <property name="defaultEncoding" value="utf-8"/>
    <!--上传文件大小限制-->
    <!--<property name="maxUploadSize" value=""/>
    <property name="maxInMemorySize" value=""/>-->
 </bean>

3.编写文件上传Controller

• 方式一：

  @Controller
  public class FileController {
      //@RequestParam("file") 将name=file控件得到的文件封装成CommonsMultipartFile 对象
      //批量上传CommonsMultipartFile则为数组即可
      @RequestMapping("/upload")
      public String fileUpload(@RequestParam("file") CommonsMultipartFile file , HttpServletRequest request) throws IOException {
  
          //获取文件名 : file.getOriginalFilename();
          String uploadFileName = file.getOriginalFilename();
  
          //如果文件名为空，直接回到首页！
          if ("".equals(uploadFileName)){
              return "redirect:/index.jsp";
          }
          System.out.println("上传文件名 : "+uploadFileName);
  
          //上传路径保存设置
          String path = request.getServletContext().getRealPath("/upload");
          //如果路径不存在，创建一个
          File realPath = new File(path);
          if (!realPath.exists()){
              realPath.mkdir();
          }
          System.out.println("上传文件保存地址："+realPath);
  
          InputStream is = file.getInputStream(); //文件输入流
          OutputStream os = new FileOutputStream(new File(realPath,uploadFileName)); //文件输出流
  
          //读取写出
          int len=0;
          byte[] buffer = new byte[1024];
          while ((len=is.read(buffer))!=-1){
              os.write(buffer,0,len);
              os.flush();
          }
          os.close();
          is.close();
          return "redirect:/index.jsp";
      }
  }
  

• 方式二：

  /*
   * 采用file.Transto 来保存上传的文件
   */
  @RequestMapping("/upload2")
  public String  fileUpload2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
  
      //上传路径保存设置
      String path = request.getServletContext().getRealPath("/upload");
      File realPath = new File(path);
      if (!realPath.exists()){
          realPath.mkdir();
      }
      //上传文件地址
      System.out.println("上传文件保存地址："+realPath);
  
      //通过CommonsMultipartFile的方法直接写文件（注意这个时候）
      file.transferTo(new File(realPath +"/"+ file.getOriginalFilename()));
  
      return "redirect:/index.jsp";
  }
  

文件下载

@Controller
public class FileController {
    @RequestMapping(value="/download")
    public String downloads(HttpServletResponse response ,HttpServletRequest request) throws Exception{
        //要下载的图片地址
        String  path = request.getSession().getServletContext().getRealPath("/static");
        String  fileName = "1.png";
        //1、设置response 响应头
        response.reset(); //设置页面不缓存,清空buffer
        response.setCharacterEncoding("UTF-8"); //字符编码
        response.setContentType("multipart/form-data"); //二进制传输数据
        //设置响应头
        response.setHeader("Content-Disposition",
                "attachment;fileName="+URLEncoder.encode(fileName, "UTF-8"));

        File file = new File(path,fileName);
        //2、 读取文件--输入流
        InputStream input=new FileInputStream(file);
        //3、 写出文件--输出流
        OutputStream out = response.getOutputStream();

        byte[] buff =new byte[1024];
        int index=0;
        //4、执行 写出操作
        while((index= input.read(buff))!= -1){
            out.write(buff, 0, index);
            out.flush();
        }
        out.close();
        input.close();
        return null;
    }
}