Servlet文件上传

Servlet实现文件上传

由于步骤相对比较固定，所以本文只记录核心步骤，其他步骤一般可以想出来，想不出来去翻这一篇博客：servlet-文件上传-狂神笔记 - 你我不在年少 - 博客园 (cnblogs.com)

步骤一：导入包

①commons-io依赖

②commons-fileupload依赖

步骤二：获取DiskFileItemFactory对象

/**
     * 获取DiskFileItemFactory对象
     *
     * @param tempfile 文件临时存储路径
     * @return
     */
public static DiskFileItemFactory getDiskFileItemFactory(File tempfile) {
    DiskFileItemFactory factory = new DiskFileItemFactory();

    //文件大于2M，由内存转存到临时文件中
    factory.setSizeThreshold(1024 * 1024 * 2);
    //临时文件存储路径
    factory.setRepository(tempfile);

    return factory;
}

步骤三：获取ServletFileUpload对象

构造方法中可以传入步骤二中获取到的DiskFileItemFactory对象

/**
* 获取ServletFileUpload对象
*
* @param factory
* @return
*/
public static ServletFileUpload getServletFileUpload(DiskFileItemFactory factory) {
    ServletFileUpload upload = new ServletFileUpload(factory);

    //读取单个部分标题时，设置编码格式
    upload.setHeaderEncoding("utf-8");
    //单个文件最大20M
    upload.setFileSizeMax(1024 * 1024 * 100);
    //最多上传20M
    upload.setSizeMax(1024 * 1024 * 100);

    //监听上传进程
    upload.setProgressListener(new ProgressListener() {
        @Override
        public void update(long pBytesRead, long pContentLength, int pItems) {
            //计算百分比
            //                double percentResult = (pBytesRead / (double) pContentLength);
            System.out.println("总大小：" + pContentLength + "    已上传" + pBytesRead);
        }
    });

    return upload;
}

步骤三：解析请求，获取文件，返回结果

//解析请求并返回结果
public String parseUploadRequest(HttpServletRequest request, ServletFileUpload upload, String uploadPath) throws FileUploadException, IOException {
    List<FileItem> fileItems = upload.parseRequest(request);
    String msg = "";

    for (FileItem fileItem : fileItems) {
        if (fileItem.isFormField()) {
            //如果是简单的表单字段，返回true；如果代表上传的文件，返回false
            continue;
        } else {
            if (fileItem.getName().trim().equals("") || fileItem.getName() == null) {
                //文件名不合乎规则
                continue;
            } else {
                //文件名
                String uploadFileName = fileItem.getName();
                System.out.println("uploadFileName" + uploadFileName);

                //一般uploadFileName是单纯的文件名，但有些浏览器也会把路径给带上去，所以这里要再过滤一下
                //lastindexof找不到返回-1
                //substring从下标0开始
                String fileName = uploadFileName.substring(uploadFileName.lastIndexOf("/") + 1);
                System.out.println("fileName:" + fileName);
                //后缀名
                String fileExtName = uploadFileName.substring(uploadFileName.lastIndexOf(".") + 1);
                System.out.println("fileExtName:" + fileExtName);

                //输出到服务器上
                //可能需要用到UUID
                InputStream inputStream = fileItem.getInputStream();
                //                FileOutputStream fos = new FileOutputStream(uploadPath + "/" + fileName + "." + fileExtName);
                //使用UUID确保文件名唯一性
                String uuidStirng = UUID.randomUUID().toString();
                FileOutputStream fos = new FileOutputStream(uploadPath + "/" + uuidStirng + "." + fileExtName);

                byte[] buffer = new byte[1024 * 1024];

                while (inputStream.read(buffer) > 0) {
                    fos.write(buffer);
                }

                fos.flush();
                fos.close();

                inputStream.close();
                msg = "文件上传成功";
            }
        }
        fileItem.delete();
    }
    return msg;
}

小结

步骤相对固定。但其中还会有些许其他小技巧，如：获取文件名、借助UUID编号保持文件名唯一性。