Java中文件下载上传常出现的几种问题

下载文件名乱码问题（Java后端）

1、第一种修改编码方式

		String fileName = fileName+".xls";
		String fileNameURL = URLEncoder.encode(fileName, "UTF-8");
		response.setHeader("Content-disposition", "attachment;filename="+fileNameURL+";"+"filename*=utf-8''"+fileNameURL);

1、第二种修改编码方式

		String userAgent = request.getHeader("User-Agent");
        String formFileName = "员工表.xls";
		// 针对IE或者以IE为内核的浏览器：
        if (userAgent.contains("MSIE") || userAgent.contains("Trident")) {
            formFileName = java.net.URLEncoder.encode(formFileName, "UTF-8");
        } else {
            // 非IE浏览器的处理：
            formFileName = new String(formFileName.getBytes("UTF-8"), "ISO-8859-1");
        }
        

1、第三种修改编码方式

        response.setHeader("Content-disposition",
                "attachment;filename=" + URLEncoder.encode("员工表.xls","UTF-8"));
        response.setContentType("application/msexcel;charset=UTF-8");
        response.setCharacterEncoding("UTF-8");
        

前端处理编码问题

function download(fileName, fileData) {
    let a = document.createElement('a'); //创建a标签
    a.setAttribute('href', fileData);
    a.setAttribute('download', fileName);
    a.setAttribute('target', '_blank'); //打开一个新的窗口
    a.setAttribute('id', "downLoad");
    if (document.getElementById('downLoad')) {
    document.body.removeChild(document.getElementById('downLoad'));
    }
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
}
//编码定义
let data = "data:image/jpeg;base64,'' ";
download('爱因斯坦', data);

各种文件的编码定义

文件的转换问题

1、将文件转换成base64

	/**
     * 将文件转为base64
     */
    public static String getBase64FromFile(File file) throws IOException {
        FileInputStream in = null;
        ByteArrayOutputStream out = null;
        try {
            in = new FileInputStream(file);
            out = new ByteArrayOutputStream();
            int read = 0;
            byte[] buffer = new byte[1024];
            while ((read = in.read(buffer, 0, 1024)) != -1) {
                out.write(buffer, 0, read);
            }
 
            return Base64.getEncoder().encodeToString(out.toByteArray());
        } catch (IOException e) {
            throw e;
        } finally {
            if (in != null) {
                in.close();
            }
            if (out != null){
                out.close();
            }
        }
    }

2、将MultipartFile转换为File

    /**
     * 将MultipartFile转换为File
     */
    public static File MultipartFileToFile(MultipartFile multiFile) throws IOException {
        String fileName = multiFile.getOriginalFilename();
        String prefix = fileName.substring(fileName.lastIndexOf("."));
        InputStream in = null;
        OutputStream out = null;
        try {
            File file = File.createTempFile(fileName, prefix);
            out = new FileOutputStream(file);
            in = multiFile.getInputStream();
            int read = 0;
            byte[] buffer = new byte[1024];
            while ((read = in.read(buffer, 0, 1024)) != -1) {
                out.write(buffer, 0, read);
            }
 
            return file;
        } catch (Exception e) {
            throw e;
        }finally {
            if (in != null){
                in.close();
            }
            if (out != null){
                out.close();
            }
        }
    }

response.setContentType()的String参数及对应类型

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本文链接：https://blog.csdn.net/Boy_Martin/article/details/126290873