Spring MVC實現文件上傳和下載

<!--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（10485760=10M） -->
 <property name="maxUploadSize" value="10485760"/>
 <property name="maxInMemorySize" value="40960"/>
</bean>

@RestController
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();
        }
        System.out.println("上傳文件保存地址：" + realPath);
        //通過CommonsMultipartFile的方法直接寫文件（註意這個時候）
        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"); //二進制傳輸數據
    //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、執行 寫出操作
    while ((index = input.read(buff)) != -1) {
        out.write(buff, 0, index);
        out.flush();
    }
    out.close();
    input.close();
    return null;
}