Flutter图片上传OSS

目前阿里没有针对Flutter有官方SDK可集成, 但是有人对Flutter的上传有封装库https://pub.dev/packages/aly_oss#-example-tab-, 所以我们只能通过post提交PostObject的形式来上传;

准备工作:

1、获取OSS凭证地址(your oss_sts_server), 通知get直接获取static String ossServerUrl = 'http://.../sts-server/sts.php';

2、上传的存储地址(桶名):static String ossEndPointCdn = '<your endpointcdn>';

// 通过ossServerUrl直接get获取到如下数据
{
        "StatusCode": 200,
          "AccessKeyId": "STS.NSsrKZes4cqm.....",
          "AccessKeySecret": "7eGnLZaEFsRCGYJAnrtdE9n.....",
          "Expiration": "2020-04-08T03:44:21Z",
          "SecurityToken": "CAISlQJ1q6Ft5B2y....."
  }

//表单需要的参数: AccessKeyId、AccessKeySecret、SecurityToken;
FormData formdata = new FormData.from({
        //文件名，随意
        'Filename': OssUtil.instance.getImageName(filePath),
        //"可以填写文件夹名（对应于oss服务中的文件夹）/" + fileName
        'key': uploadName,//上传后的文件名
        'policy': OssUtil.policy,
        //Bucket 拥有者的AccessKeyId。
        'OSSAccessKeyId': data['AccessKeyId'],
        //让服务端返回200，不然，默认会返回204
        'success_action_status': '200',
        'signature': OssUtil.instance.getSignature(data['AccessKeySecret']),
        //临时用户授权时必须，需要携带后台返回的security-token
        'x-oss-security-token': data['SecurityToken'],
        'file': new UploadFileInfo(
            file, OssUtil.instance.getImageNameByPath(filePath))
        //必须放在参数最后
   });
//然后通过存储地址直接把表单(formdata)上传上去;
Dio dio=Dio();
dio.options.responseType=ResponseType.plain;
Response response=awaitdio.post(<ossEndPointCdn>,data:formData);
......

tips: 上传成功后图片地址 imageUrl = ossEndPointCdn + '/' + uploadName;

给一个工具类

import 'dart:convert';
import 'package:crypto/crypto.dart';
import 'dart:math';

class OssUtil {
 获取
  //验证文本域
  static String _policyText =
      '{"expiration": "2069-05-22T03:15:00.000Z","conditions": [["content-length-range", 0, 1048576000]]}';//UTC时间+8=北京时间

  //进行utf8编码
  // ignore: non_constant_identifier_names
  static List<int> _policyText_utf8 = utf8.encode(_policyText);
  //进行base64编码
  static String policy= base64.encode(_policyText_utf8);

  //再次进行utf8编码
  // ignore: non_constant_identifier_names
  static List<int> _policy_utf8 = utf8.encode(policy);

  // 工厂模式
  factory OssUtil() => _getInstance();

  static OssUtil get instance => _getInstance();
  static OssUtil _instance;

  OssUtil._internal();

  static OssUtil _getInstance() {
    if (_instance == null) {
      _instance = new OssUtil._internal();
    }
    return _instance;
  }

  /*
  *获取signature签名参数
  */
  String getSignature(String _accessKeySecret){
    //进行utf8 编码
    // ignore: non_constant_identifier_names
    List<int> AccessKeySecretUtf8 = utf8.encode(_accessKeySecret);
    //通过hmac,使用sha1进行加密
    List<int> signaturePre = new Hmac(sha1, AccessKeySecretUtf8).convert(_policy_utf8).bytes;
    //最后一步，将上述所得进行base64 编码
    String signature = base64.encode(signaturePre);
    return signature;
  }

  // ignore: slash_for_doc_comments
  /**
   * 生成上传上传图片的名称 ,获得的格式:photo/20171027175940_oCiobK
   * 可以定义上传的路径uploadPath(Oss中保存文件夹的名称)
   * @param uploadPath 上传的路径 如：/photo
   * @return photo/20171027175940_oCiobK
   */
  String getImageUploadName(String uploadPath,String filePath) {
    String imageMame = "";
    var timestamp = new DateTime.now().millisecondsSinceEpoch;
    imageMame =timestamp.toString()+"_"+getRandom(6);
    if(uploadPath!=null&&uploadPath.isNotEmpty){
      imageMame=uploadPath+"/"+imageMame;
    }
    String imageType=filePath?.substring(filePath?.lastIndexOf("."),filePath?.length);
    return imageMame+imageType;
  }

  String getImageName(String filePath) {
    String imageMame = "";
    var timestamp = new DateTime.now().millisecondsSinceEpoch;
    imageMame =timestamp.toString()+"_"+getRandom(6);
    String imageType=filePath?.substring(filePath?.lastIndexOf("."),filePath?.length);
    return imageMame+imageType;
  }

  /*
  * 生成固定长度的随机字符串
  * */
  String getRandom(int num) {
    String alphabet = 'qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM';
    String left = '';
    for (var i = 0; i < num; i++) {
//    right = right + (min + (Random().nextInt(max - min))).toString();
      left = left + alphabet[Random().nextInt(alphabet.length)];
    }
    return left;
  }

  /*
  * 根据图片本地路径获取图片名称
  * */
  String getImageNameByPath(String filePath) {
    // ignore: null_aware_before_operator
    return filePath?.substring(filePath?.lastIndexOf("/")+1,filePath?.length);
  }
}