文件下载回显

首先思路是给前端一个url（里面的动作是赋值输出流）

1.上传byte[]

public byte[] uploadbyte(MultipartFile[] files, MarketChannelSaveRequest saveRequest, HttpServletRequest request) {
    String listFileStr = "";
    try {
        for (int i = 0; i < files.length; i++) {
            MultipartFile file = files[i];
            String fileName = file.getOriginalFilename();
            byte[] bytes = file.getBytes();
            String hexString = byteToHex(bytes);
            listFileStr += fileName + "=" + hexString + ",";
        }
        listFileStr = listFileStr.substring(0, listFileStr.length() - 1);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return ZipUtil.gzip(listFileStr, "UTF-8");
}
//转16进制 方便存储

public String byteToHex(byte[] buf) {
    StringBuilder sb = new StringBuilder(buf.length * 2);
    for (byte b : buf) {
        sb.append(String.format("%02x", new Integer(b & 0xff)));
    }
    return sb.toString();
}
2.获取byte

public String download(String id) {
    MarketChannel marketChannel = marketChannelDao.queryById(id);
    String listFileStrs = ZipUtil.unGzip(marketChannel.getEmailAttachment(),"UTF-8");
    return listFileStrs;

}
获取文件名和id byte

  String listFileStrs = this.download(channelId);
    String[] bytesStrs = listFileStrs.split(",");
    for (int i = 0; i < bytesStrs.length; i++) {
        ShowBackResponse showBackResponse = new ShowBackResponse();
        String[] files = bytesStrs[i].toString().split("=");
        String fileName = files[0];
        String byteStr = files[1];
        showBackResponse.setName(fileName);
        showBackResponse.setId(channelId);
        appPushShowBackResponses.add(showBackResponse);
    }
}
return appPushShowBackResponses;
回显 注 先赋值contentType 强制为下载 后赋值为直接展示

String channelId = id;
String listFileStrs = this.download(channelId);
String[] bytesStrs = listFileStrs.split(",");
for (int i = 0; i < bytesStrs.length; i++) {
    String[] files = bytesStrs[i].toString().split("=");
    String fileName = files[0];
    if(fileName.equals(name)){
        OutputStream outputStream = null;
        try {
            outputStream = response.getOutputStream();
            String byteStr = files[1];
            byte[] bytes= this.hexToByteArray(byteStr);
            outputStream.write(bytes);
            response.setContentType("application/octet-stream");
            response.setCharacterEncoding("UTF-8");
            response.setHeader("Content-Disposition", "attachment;filename="+fileName);
            //outputStream.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                outputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }else {
        continue;
    }
}

16进制转回2进制
/**
 * hex字符串转byte数组
 * @param inHex 待转换的Hex字符串
 * @return  转换后的byte数组结果
 */
public static byte[] hexToByteArray(String inHex){
    int hexlen = inHex.length();
    byte[] result;
    if (hexlen % 2 == 1){
        //奇数
        hexlen++;
        result = new byte[(hexlen/2)];
        inHex="0"+inHex;
    }else {
        //偶数
        result = new byte[(hexlen/2)];
    }
    int j=0;
    for (int i = 0; i < hexlen; i+=2){
        result[j]=hexToByte(inHex.substring(i,i+2));
        j++;
    }
    return result;
}

/**
 * Hex字符串转byte
 * @param inHex 待转换的Hex字符串
 * @return  转换后的byte
 */
public static byte hexToByte(String inHex){
    return (byte)Integer.parseInt(inHex,16);
}