java 上传下载文件

// java
public String uploadFile(MultipartFile[] files) {
    if (files != null && files.length > 0) {
        for (MultipartFile mf : files) {
            String fileName = mf.getOriginalFilename(); // 获取文件名称
            String suffix = fileName.substring(fileName.lastIndexOf(".")); // 获取文件后缀
            String fileRealName = DateUtil.getStringMillisecond() + suffix; // 存储的文件名
            File file = new File(init.getFileManagePath() + File.separator + fileRealName);
            if (!file.exists()) {
                file.mkdirs();
            }
            try {
                mf.transferTo(file); // 存入磁盘
                // 数据入库
                FileManage fileManage = new FileManage();
                fileManage.setFilePath(init.getFileManagePath());
                fileManage.setFileName(fileName);
                fileManage.setFileRealName(fileRealName);
                fileManageMapper.addFile(fileManage);
            } catch (IOException e) {
                e.printStackTrace();
                return "fail";
            }
        }
    }
    return "success";
}


public void downloadFile(HttpServletResponse response, Long fileId) {
    FileManage fileManage = fileManageMapper.findById(fileId);

    String filePath = fileManage.getFilePath() + File.separator + fileManage.getFileRealName();
    String fileName = fileManage.getFileName();
    try {
        response.setHeader("content-disposition", "attachment;fileName=\""+ URLEncoder.encode(fileName,"UTF-8")+"\"");
        FileInputStream fis = new FileInputStream(filePath);
        BufferedInputStream bis = new BufferedInputStream(fis);
        byte[] buffer = new byte[fis.available()];
        fis.read(buffer);
        fis.close();
        OutputStream os = new BufferedOutputStream(response.getOutputStream());
        os.write(buffer);
        os.flush();
        os.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

// html

<form id="uploadFileForm" enctype="multipart/form-data" style="display: none">
    <input type="file" name="file" id="resultFile" multiple="multiple" hidden="hidden" onchange="uploadMoreFile()"/>
</form>

<input type="button" value="上传文件" id="resultUpload" onclick="$('#resultFile').click()" />

// js

// 多文件上传
function uploadMoreFile(){
    let formData = new FormData($("#uploadFileForm")[0]);
    $.ajax({
        type: 'post',
        url: webUrl+"/manage/file/uploadFile.action",
        data: formData,
        processData: false,
        contentType: false,
    }).success(function (data) {
        loadFileList();
    }).error(function () {});
}
// 下载

function downloadFileM(fileId) {
   let form = $("<form>");
   form.attr("style","display:none");
   form.attr("action",webUrl+"/web/file/downloadFile.action");
   form.attr("method","post");
   $('body').append(form);
   let input = $("<input>");
   input.attr("type","hidden");
   input.attr("name","fileId");
   input.attr("value",fileId);
   form.append(input);
   form.submit();
   form.remove();
}