<dependency>

 <groupId>org.apache.commons</groupId>

 <artifactId>commons-io</artifactId>

 <version>1.3.2</version>

 </dependency>

使用Intellij IDEA生成預設SpringBoot專案不含webapp資料夾，如果沒有找到webapp，

request.getSession().getServletContext().getRealPath("/") 

獲取到的是C盤的臨時目錄建立在src/main下建立webapp即可解決
 

一，設定上傳檔案大小

可以在啟動類中建立如下方法配置上傳大小

 @Bean
    public MultipartConfigElement multipartConfigElement(){
        MultipartConfigFactory multipartConfigFactory = new MultipartConfigFactory();
        multipartConfigFactory.setMaxFileSize("24MB");
        multipartConfigFactory.setMaxRequestSize("20MB");
        return multipartConfigFactory.createMultipartConfig();
    }
 

@Configuration

二，controller中方法

1，上傳

@PostMapping(value = "/upload")
    public @ResponseBody String upload(@RequestParam("file") MultipartFile file, HttpServletRequest request) throws IOException {
        String contentType = file.getContentType();
        String fileName = file.getOriginalFilename();
        System.out.println(fileName);

        String filePath = request.getSession().getServletContext().getRealPath("/") + "upload\\";
        System.out.println(filePath);
        if (!file.isEmpty()){
            File targetFile = new File(filePath + fileName);
            if (!targetFile.exists()){
                targetFile.createNewFile();
            }
            file.transferTo(targetFile);
        }
        return "upload success";
    }
 

2.，下載

@RequestMapping(value = "/download",method = RequestMethod.GET)
    public ResponseEntity<byte[]> dowonload(HttpServletRequest request) throws IOException {
        String path = request.getSession().getServletContext().getRealPath("/") + "upload\\";
        File file = new File(path + "/symbol-check.png");
        HttpHeaders headers = new HttpHeaders();
        headers.setContentDispositionFormData("attachment","symbol-check.png");
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file), headers, HttpStatus.CREATED);
    }

3，前臺

<form id="fileForm" name="fileForm" enctype="multipart/form-data">
<input type="file" name="file" id="file"/>
<button id="btn" type="button">提交</button>
</form>
<a href="download">下載</a>

 $(function () {
        $("#btn").click(function () {
            $.ajax({
                type: "POST",
                url: "upload",
                contentType: false,
                processData: false,
                data: new FormData($("#fileForm")[0]),
                success: function (data) {
                    alert(data)
                }
            });
        });
    });