后端文件上传（图片）

引入缩略图依赖

<!--缩略图相关依赖-->
  <dependency>
    <groupId>net.coobird</groupId>
    <artifactId>thumbnailator</artifactId>
    <version>0.4.8</version>
  </dependency>

后台接口代码

上传

import com.wuxiapptec.uniteplatform.rest.modular.domain.util.Encodes;
import com.wuxiapptec.uniteplatform.rest.modular.domain.util.Digests;

private static final String FILE_SEPARATOR = "/";

@RequestMapping(value = "/upload", method = RequestMethod.POST)
    public ResponseEntity<?> upload(@RequestPart("file") MultipartFile file) throws IOException {
        log4.info("上传文件");
        Map<String, String> result = new HashMap<>();
        if (file.isEmpty()) {
            log4.info("上传文件为空！");
            result.put("msg","上传文件不能为空");
            return new ResponseEntity<>(result, HttpStatus.NO_CONTENT);
        }
        String url = "";
        try {
            byte[] fileBytes = null;
            try {
                fileBytes = file.getBytes();
            } catch (final IOException e1) {
                e1.printStackTrace();
            }
            final String name = file.getOriginalFilename();
            final String md5 = Encodes.encodeHex(Digests.md5(fileBytes));
            StringBuilder path = getPath(md5);
            path = path.append(name);
            // 获取服务器文件资源保存路径(保存在数据库中)
            String serverFileSavePath = settingMapper.getSetValue("FileSavePath");;
            if (StringUtils.isEmpty(serverFileSavePath)) {
                result.put("msg","服务器文件保存路径为空");
                return new ResponseEntity<>(result, HttpStatus.INTERNAL_SERVER_ERROR);
            }
            String filePath = serverFileSavePath + FILE_SEPARATOR + path.toString();

            File localFile = null;
            try {
                localFile = new File(filePath);
                localFile.getParentFile().mkdirs();
                Files.write(fileBytes,localFile);
            } catch (final IOException e) {
                log4.error("保存文件失败: {}", e);
            }
            url = fileSavePath + FILE_SEPARATOR + md5 + FILE_SEPARATOR + name;
            // 缩略图名称添加固定后缀
            int i = name.lastIndexOf(".");
            String newName = name.substring(0,i) + "_thumbnail" + name.substring(i);
            String path2 = serverFileSavePath + FILE_SEPARATOR + getPath(md5).toString() + newName;
            // 按照一定比例生成缩略图
Thumbnails.of(localFile).scale(0.04f).outputQuality(1.0f).toFile(path2);
            String zoomOutUrl = fileSavePath + FILE_SEPARATOR + md5 + FILE_SEPARATOR + newName;
            // 返回原图和缩略图的url请求路径
            result.put("url",url);
            result.put("smallUrl",zoomOutUrl);
        } catch (final Exception e){
            log4.error("保存文件失败: {}", e);
            new ResponseEntity<>(result, HttpStatus.INTERNAL_SERVER_ERROR);
        }
        return new ResponseEntity<>(result, HttpStatus.OK);
    }
    /**
     * 获取上传文件的路径
     * @param md5
     * @return
     */
    private StringBuilder getPath(String md5) {
        final StringBuilder sb = new StringBuilder();
        // @formatter:off
        sb.append(StringUtils.left(md5, 2))
                .append(FILE_SEPARATOR)
                .append(StringUtils.mid(md5, 2, 2))
                .append(FILE_SEPARATOR)
                .append(md5)
                .append(FILE_SEPARATOR);
        // @formatter:off
        return sb;
    }

下载

import java.net.URLEncoder;
/**
     * 获取文件
     *
     * @param p
     * @param name
     * @param request
     * @param response
     * @throws IOException
     */
    @RequestMapping(value = "/{p}/{name:.+}", method = RequestMethod.GET)
    public void download(@PathVariable("p") String p, @PathVariable("name") String name, HttpServletRequest request,
                         HttpServletResponse response) throws IOException {
        log4.info("文件资源获取");
        // get absolute path of the application
        final ServletContext context = request.getServletContext();
        final String appPath = context.getRealPath("");
        System.out.println("appPath = " + appPath);

        // construct the complete absolute path of the file
        final String fullPath = p + "/" + name;
        // 调用service解析请求路径获取对应文件
        final File downloadFile = fileService.downloadFile(fullPath);
        final FileInputStream inputStream = new FileInputStream(downloadFile);

        // get MIME type of the file
        String mimeType = context.getMimeType(fullPath);
        if (mimeType == null) {
            // set to binary type if MIME mapping not found
            mimeType = "application/octet-stream";
        }
        System.out.println("MIME type: " + mimeType);

        // set content attributes for the response
        response.setContentType(mimeType);
        response.setContentLength((int) downloadFile.length());

        // set headers for the response
        final String headerKey = "Content-Disposition";
        String fileName = URLEncoder.encode(downloadFile.getName(),"UTF-8");
        final String headerValue = String.format("attachment; filename=\"%s\"",
                fileName);
        response.setHeader(headerKey, headerValue);

        // get output stream of the response
        final OutputStream outStream = response.getOutputStream();

        IOUtils.copy(inputStream, outStream);

        inputStream.close();
        outStream.close();

    }

service解析路径

import org.apache.commons.lang3.time.DateUtils;

    private static String[] parsePatterns = {"yyyy-MM-dd","yyyy年MM月dd日",
            "yyyy-MM-dd HH:mm:ss", "yyyy-MM-dd HH:mm", "yyyy/MM/dd",
            "yyyy/MM/dd HH:mm:ss", "yyyy/MM/dd HH:mm", "yyyyMMdd","yyyyMMddHHmmss"};

/**
     * 下载文件
     * @param path
     * @return
     * @throws IOException
     */
    public File downloadFile(String path) throws IOException {

        final String[] paths = path.split("/");
        final String p3 = paths[0];
        final String name = paths[1];
        final String p1 = StringUtils.left(p3, 2);
        final String p2 = StringUtils.mid(p3, 2, 2);
        // 获取服务器文件资源保存路径
        String fileSavePath = "";
        StringBuilder sb;
        try {
        // 根据不同的业务情况解析路径，获取文件的保存路径
            if (p3.contains("-")) {
                String[] tempPath = p3.split("-");
                fileSavePath = settingMapper.getSetValue("ImportModule");
                sb = new StringBuilder(fileSavePath).append(File.separator).append(tempPath[0]).append(File.separator)
                        .append(tempPath[1]).append(File.separator).append(name);
            } else {
                // 如果是日期格式则是excel
                DateUtils.parseDate(p3, parsePatterns);
                fileSavePath = settingMapper.getSetValue("ExcelSavePath");
                sb = new StringBuilder(fileSavePath).append(File.separator).append(p3).append(File.separator).append(name);
            }
        } catch (ParseException e) {
            fileSavePath = settingMapper.getSetValue("FileSavePath");
            sb = new StringBuilder(fileSavePath).append(File.separator).append(p1).append(File.separator).append(p2)
                    .append(File.separator).append(p3).append(File.separator).append(name);
        }

        final File file = new File(sb.toString());
        return file;
    }

ps：上述方法为当前业务案例，根据文件上传时的保存路径及返回的url，在下载时实现对应的解析，此处仍需完善