微信小程序请求服务端签名，直连上传图片到OSS

• JDK版本：1.8
• oss sdk版本：aliyun-sdk-oss3.15.2
• 服务端签名

   long expireEndTime = System.currentTimeMillis() + 21600* 1000  ;
            Date expiration = new Date(expireEndTime);
            // 上传空间
            String uploadDir = DateTimeUtils.getDateTime("yyyyMMdd", expiration);
            PolicyConditions policyCons = new PolicyConditions();
            policyCons.addConditionItem(PolicyConditions.COND_CONTENT_LENGTH_RANGE, 0, 1048576000);
            policyCons.addConditionItem(MatchMode.StartWith, PolicyConditions.COND_KEY, uploadDir);
            // 生成post请求策略
            String postPolicy = ossClient().generatePostPolicy(expiration, policyCons);
            byte[] binaryData = postPolicy.getBytes(StandardCharsets.UTF_8);
            String encodedPolicy = BinaryUtil.toBase64String(binaryData);
            // 生成签名用于直连上传
            String postSignature = ossClient().calculatePostSignature(postPolicy);
            // 构建
            OssPolicy ossPolicy = new OssPolicy();
            ossPolicy.setPolicy(encodedPolicy);
            ossPolicy.setAccessKeyId(ossConfig().getAccessKeyId());
            ossPolicy.setSignature(postSignature);
            ossPolicy.setExpireEndTime((expireEndTime - 28800 * 1000)/ 1000);
            ossPolicy.setDir(uploadDir);
            // 前端上传域名
            ossPolicy.setHost(ossConfig().getHost());

• 小程序直连上传

        let imgSignature = {}
		if (!oldExpireEndTime || oldExpireEndTime <= Math.round(new Date().getTime() / 1000)) {
			const { data } = await that.$api.generatePolicy()
			imgSignature = data.body
			uni.setStorageSync("imgSignature", imgSignature)
		} else {
			imgSignature = uni.getStorageSync("imgSignature")
		}
		const { accessKeyId, policy, signature, dir, host, expireEndTime } = imgSignature
		const key = `${dir}/user-${userId}-${new Date().getTime()}.png`
		const queryInfo = {
			key,
			policy,
			OSSAccessKeyId: accessKeyId,
			signature,
			expireEndTime,
		}
		uni.uploadFile({
			url: host,
			filePath,
			name: "file",
			formData: queryInfo,
			success: (res) => {
				
				if (res.statusCode === 204) resolve(host + "/" + key)
				else reject()
			},
			fail: (err) => {
				
				reject()
			},
		})

• 出现问题 Invalid according to Policy: Policy expired。policy的过期时间设置为六个小时了。