<form action="" enctype="multipart/form-data" method="post">
  <input type="file" name="file"/>
  <input type="submit">
</form>

<!--文件上傳-->
<dependency>
  <groupId>commons-fileupload</groupId>
  <artifactId>commons-fileupload</artifactId>
  <version>1.3.3</version>
</dependency>
<!--servlet-api導入高版本的-->
<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>javax.servlet-api</artifactId>
  <version>4.0.1</version>
</dependency>

<!--文件上傳配置-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
  <!-- 請求的編碼格式，必須和jSP的pageEncoding屬性一致，以便正確讀取表單的內(nèi)容，默認為ISO-8859-1 -->
  <property name="defaultEncoding" value="utf-8"/>
  <!-- 上傳文件大小上限，單位為字節(jié)（10485760=10M） -->
  <property name="maxUploadSize" value="10485760"/>
  <property name="maxInMemorySize" value="40960"/>
</bean>

<form action="/upload" enctype="multipart/form-data" method="post">
 <input type="file" name="file"/>
 <input type="submit" value="upload">
</form>

package com.xiaohua.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.commons.CommonsMultipartFile;

import javax.servlet.http.HttpServletRequest;
import java.io.*;

@Controller
public class FileController {
  //@RequestParam("file") 將name=file控件得到的文件封裝成CommonsMultipartFile 對象
  //批量上傳CommonsMultipartFile則為數(shù)組即可
  @RequestMapping("/upload")
  public String fileUpload(@RequestParam("file") CommonsMultipartFile file , HttpServletRequest request) throws IOException {

    //獲取文件名 : file.getOriginalFilename();
    String uploadFileName = file.getOriginalFilename();

    //如果文件名為空，直接回到首頁！
    if ("".equals(uploadFileName)){
      return "redirect:/index.jsp";
    }
    System.out.println("上傳文件名 : "+uploadFileName);

    //上傳路徑保存設置
    String path = request.getServletContext().getRealPath("/upload");
    //如果路徑不存在，創(chuàng)建一個
    File realPath = new File(path);
    if (!realPath.exists()){
      realPath.mkdir();
    }
    System.out.println("上傳文件保存地址："+realPath);

    InputStream is = file.getInputStream(); //文件輸入流
    OutputStream os = new FileOutputStream(new File(realPath,uploadFileName)); //文件輸出流

    //讀取寫出
    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";
  }
}

/*
 * 采用file.Transto 來保存上傳的文件
 */
@RequestMapping("/upload2")
public String fileUpload2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {

  //上傳路徑保存設置
  String path = request.getServletContext().getRealPath("/upload");
  File realPath = new File(path);
  if (!realPath.exists()){
    realPath.mkdir();
  }
  //上傳文件地址
  System.out.println("上傳文件保存地址："+realPath);

  //通過CommonsMultipartFile的方法直接寫文件（注意這個時候）
  file.transferTo(new File(realPath +"/"+ file.getOriginalFilename()));

  return "redirect:/index.jsp";
}

@RequestMapping(value="/download")
public String downloads(HttpServletResponse response ,HttpServletRequest request) throws Exception{
  //要下載的圖片地址
  String path = request.getServletContext().getRealPath("/upload");
  String fileName = "基礎語法.jpg";

  //1、設置response 響應頭
  response.reset(); //設置頁面不緩存,清空buffer
  response.setCharacterEncoding("UTF-8"); //字符編碼
  response.setContentType("multipart/form-data"); //二進制傳輸數(shù)據(jù)
  //設置響應頭
  response.setHeader("Content-Disposition",
      "attachment;fileName="+URLEncoder.encode(fileName, "UTF-8"));

  File file = new File(path,fileName);
  //2、 讀取文件--輸入流
  InputStream input=new FileInputStream(file);
  //3、 寫出文件--輸出流
  OutputStream out = response.getOutputStream();

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