当前位置：主页 > 查看内容

使用URL进行授权访问_对象存储服务 OBS_SDK参考_Java_授权访问

发布时间：2021-09-10 00:00| 有位朋友查看

简介：开发过程中，您有任何问题可以在github上提交issue ，或者在华为云对象存储服务论坛中发帖求助。接口参考文档详细介绍了每个接口的参数和使用方法。 OBS客户端支持通过访问密钥、请求方法类型、请求参数等信息生成一个在Query参数中携带鉴权信息的URL，……

开发过程中，您有任何问题可以在github上提交issue，或者在华为云对象存储服务论坛中发帖求助。接口参考文档详细介绍了每个接口的参数和使用方法。

OBS客户端支持通过访问密钥、请求方法类型、请求参数等信息生成一个在Query参数中携带鉴权信息的URL，可将该URL提供给其他用户进行临时访问。在生成URL时，您需要指定URL的有效期来限制访客用户的访问时长。

如果您想授予其他用户对桶或对象临时进行其他操作的权限（例如上传或下载对象），则需要生成带对应请求的URL后（例如使用生成PUT请求的URL上传对象），将该URL提供给其他用户。

通过该方式可支持的操作以及相关信息见下表：

操作名	HTTP请求方法（OBS Java SDK对应值）	特殊操作符（OBS Java SDK对应值）	是否需要桶名	是否需要对象名
创建桶	HttpMethodEnum.PUT	N/A	是	否
获取桶列表	HttpMethodEnum.GET	N/A	否	否
删除桶	HttpMethodEnum.DELETE	N/A	是	否
列举桶内对象	HttpMethodEnum.GET	N/A	是	否
列举桶内多版本对象	HttpMethodEnum.GET	SpecialParamEnum.VERSIONS	是	否
列举分段上传任务	HttpMethodEnum.GET	SpecialParamEnum.UPLOADS	是	否
获取桶元数据	HttpMethodEnum.HEAD	N/A	是	否
获取桶区域位置	HttpMethodEnum.GET	SpecialParamEnum.LOCATION	是	否
获取桶存量信息	HttpMethodEnum.GET	SpecialParamEnum.STORAGEINFO	是	否
设置桶配额	HttpMethodEnum.PUT	SpecialParamEnum.QUOTA	是	否
获取桶配额	HttpMethodEnum.GET	SpecialParamEnum.QUOTA	是	否
设置桶存储类型	HttpMethodEnum.PUT	SpecialParamEnum.STORAGEPOLICY	是	否
获取桶存储类型	HttpMethodEnum.GET	SpecialParamEnum.STORAGEPOLICY	是	否
设置桶访问权限	HttpMethodEnum.PUT	SpecialParamEnum.ACL	是	否
获取桶访问权限	HttpMethodEnum.GET	SpecialParamEnum.ACL	是	否
开启/关闭桶日志	HttpMethodEnum.PUT	SpecialParamEnum.LOGGING	是	否
查看桶日志	HttpMethodEnum.GET	SpecialParamEnum.LOGGING	是	否
设置桶策略	HttpMethodEnum.PUT	SpecialParamEnum.POLICY	是	否
查看桶策略	HttpMethodEnum.GET	SpecialParamEnum.POLICY	是	否
删除桶策略	HttpMethodEnum.DELETE	SpecialParamEnum.POLICY	是	否
设置生命周期规则	HttpMethodEnum.PUT	SpecialParamEnum.LIFECYCLE	是	否
查看生命周期规则	HttpMethodEnum.GET	SpecialParamEnum.LIFECYCLE	是	否
删除生命周期规则	HttpMethodEnum.DELETE	SpecialParamEnum.LIFECYCLE	是	否
设置托管配置	HttpMethodEnum.PUT	SpecialParamEnum.WEBSITE	是	否
查看托管配置	HttpMethodEnum.GET	SpecialParamEnum.WEBSITE	是	否
清除托管配置	HttpMethodEnum.DELETE	SpecialParamEnum.WEBSITE	是	否
设置桶多版本状态	HttpMethodEnum.PUT	SpecialParamEnum.VERSIONING	是	否
查看桶多版本状态	HttpMethodEnum.GET	SpecialParamEnum.VERSIONING	是	否
设置跨域规则	HttpMethodEnum.PUT	SpecialParamEnum.CORS	是	否
查看跨域规则	HttpMethodEnum.GET	SpecialParamEnum.CORS	是	否
删除跨域规则	HttpMethodEnum.DELETE	SpecialParamEnum.CORS	是	否
设置/关闭事件通知	HttpMethodEnum.PUT	SpecialParamEnum.NOTIFICATION	是	否
查看事件通知	HttpMethodEnum.GET	SpecialParamEnum.NOTIFICATION	是	否
设置桶标签	HttpMethodEnum.PUT	SpecialParamEnum.TAGGING	是	否
查看桶标签	HttpMethodEnum.GET	SpecialParamEnum.TAGGING	是	否
删除桶标签	HttpMethodEnum.DELETE	SpecialParamEnum.TAGGING	是	否
上传对象	HttpMethodEnum.PUT	N/A	是	是
追加上传	HttpMethodEnum.POST	SpecialParamEnum.APPEND	是	是
下载对象	HttpMethodEnum.GET	N/A	是	是
复制对象	HttpMethodEnum.PUT	N/A	是	是
删除对象	HttpMethodEnum.DELETE	N/A	是	是
批量删除对象	HttpMethodEnum.POST	SpecialParamEnum.DELETE	是	是
获取对象属性	HttpMethodEnum.HEAD	N/A	是	是
设置对象访问权限	HttpMethodEnum.PUT	SpecialParamEnum.ACL	是	是
查看对象访问权限	HttpMethodEnum.GET	SpecialParamEnum.ACL	是	是
初始化分段上传任务	HttpMethodEnum.POST	SpecialParamEnum.UPLOADS	是	是
上传段	HttpMethodEnum.PUT	N/A	是	是
复制段	HttpMethodEnum.PUT	N/A	是	是
列举已上传的段	HttpMethodEnum.GET	N/A	是	是
合并段	HttpMethodEnum.POST	N/A	是	是
取消分段上传任务	HttpMethodEnum.DELETE	N/A	是	是
取回归档存储对象	HttpMethodEnum.POST	SpecialParamEnum.RESTORE	是	是

通过OBS Java SDK实现URL授权访问的步骤如下：

通过ObsClient.createTemporarySignature生成带签名信息的URL。
使用任意HTTP库发送HTTP/HTTPS请求，访问OBS服务。

以下代码展示了如何使用URL进行授权访问，包括：创建桶、上传对象、下载对象、列举对象、删除对象。

创建桶

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;

TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.PUT, expireSeconds);
request.setBucketName("bucketname");
TemporarySignatureResponse response = obsClient.createTemporarySignature(request);
System.out.println("Creating bucket using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());

Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}
// 使用PUT请求创建桶
String location = "your bucket location";
Request httpRequest = builder.url(response.getSignedUrl()).put(RequestBody.create(null, "<CreateBucketConfiguration><Location>" + location + "</Location></CreateBucketConfiguration>".getBytes())).build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

上传对象

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;

Map<String, String> headers = new HashMap<String, String>();
String contentType = "text/plain";
headers.put("Content-Type", contentType);

TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.PUT, expireSeconds);
request.setBucketName("bucketname");
request.setObjectKey("objectname");
request.setHeaders(headers);

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);

System.out.println("Creating object using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());
Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}

//使用PUT请求上传对象
Request httpRequest = builder.url(response.getSignedUrl()).put(RequestBody.create(MediaType.parse(contentType), "Hello OBS".getBytes("UTF-8"))).build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

下载对象

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;


TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.GET, expireSeconds);
request.setBucketName("bucketname");
request.setObjectKey("objectname");

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);

System.out.println("Getting object using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());
Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}

//使用GET请求下载对象
Request httpRequest = builder.url(response.getSignedUrl()).get().build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

列举对象

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;


TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.GET, expireSeconds);
request.setBucketName("bucketname");

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);

System.out.println("Getting object list using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());
Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}

//使用GET请求获取对象列表
Request httpRequest = builder.url(response.getSignedUrl()).get().build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

删除对象

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;


TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.DELETE, expireSeconds);
request.setBucketName("bucketname");
request.setObjectKey("objectname");

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);

System.out.println("Deleting object using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());
Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}

//使用DELETE删除对象
Request httpRequest = builder.url(response.getSignedUrl()).delete().build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

初始化分段上传任务

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;

TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.POST, expireSeconds);
request.setBucketName("bucketname");
request.setObjectKey("objectname");
request.setSpecialParam(SpecialParamEnum.UPLOADS);

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);

System.out.println("initiate multipart upload using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());

Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}

//使用POST请求初始化分段上传任务
Request httpRequest = builder.url(response.getSignedUrl()).post(RequestBody.create(null, "")).build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

上传段

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;

TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.PUT, expireSeconds);
request.setBucketName("bucketname");
request.setObjectKey("objectname");

Map<String, Object> queryParams = new HashMap<String, Object>();
// 设置partNumber请求参数，例如：queryParams.put("partNumber", "1");
queryParams.put("partNumber", "partNumber");
queryParams.put("uploadId", "your uploadId");

request.setQueryParams(queryParams);

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);

System.out.println("upload part using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());

Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}

//使用PUT请求上传段
Request httpRequest = builder.url(response.getSignedUrl()).put(RequestBody.create(null, new byte[6 * 1024 * 1024])).build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

列举已上传段

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;

TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.GET, expireSeconds);
request.setBucketName("bucketname");
request.setObjectKey("objectname");

Map<String, Object> queryParams = new HashMap<String, Object>();
queryParams.put("uploadId", "your uploadId");
request.setQueryParams(queryParams);

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);

System.out.println("list parts using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());

Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}

//使用GET请求列举已上传段
Request httpRequest = builder.url(response.getSignedUrl()).get().build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

合并段

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;

TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.POST, expireSeconds);
request.setBucketName("bucketname");
request.setObjectKey("objectname");

Map<String, String> headers = new HashMap<String, String>();
String contentType = "application/xml";
headers.put("Content-Type", contentType);
request.setHeaders(headers);

Map<String, Object> queryParams = new HashMap<String, Object>();
queryParams.put("uploadId", "your uploadId");
request.setQueryParams(queryParams);

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);

System.out.println("complete multipart upload using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());

Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}

// 以下content为示例代码，需要通过列举已上传段方法的响应结果，拼装以下内容
String content = "<CompleteMultipartUpload>";
content += "<Part>";
content += "<PartNumber>1</PartNumber>";
content += "<ETag>da6a0d097e307ac52ed9b4ad551801fc</ETag>";
content += "</Part>";
content += "<Part>";
content += "<PartNumber>2</PartNumber>";
content += "<ETag>da6a0d097e307ac52ed9b4ad551801fc</ETag>";
content += "</Part>";
content += "</CompleteMultipartUpload>";

//使用POST请求合并段
Request httpRequest = builder.url(response.getSignedUrl()).post(RequestBody.create(MediaType.parse(contentType), content.getBytes("UTF-8"))).build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

获取图片转码的下载链接

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, endPoint);
// URL有效期，3600秒
long expireSeconds = 3600L;


TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.GET, expireSeconds);
request.setBucketName("bucketname");
request.setObjectKey("objectname");

// 设置图片转码参数

Map<String,Object> queryParams = new HashMap<String, Object>();
queryParams.put("x-image-process", "image/resize,m_fixed,w_100,h_100/rotate,100");
request.setQueryParams(queryParams);

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);
//获取支持图片转码的下载链接
System.out.println("Getting object using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());
res.close();

下载SSE-C加密类型的对象

String endPoint = "http://your-endpoint";
String ak = "*** Provide your Access Key ***";
String sk = "*** Provide your Secret Key ***";

ObsConfiguration config = new ObsConfiguration();
config.setSocketTimeout(30000);
config.setConnectionTimeout(10000);
config.setEndPoint(endPoint);
// 创建ObsClient实例
ObsClient obsClient = new ObsClient(ak, sk, config);
// URL有效期，3600秒
long expireSeconds = 3600L;

TemporarySignatureRequest request = new TemporarySignatureRequest(HttpMethodEnum.GET, expireSeconds);
request.setBucketName("bucketname");
request.setObjectKey("objectname");
// 设置SSE-C加密方式的头域信息
Map<String, String> headers = new HashMap<String, String>();
headers.put("x-obs-server-side-encryption-customer-algorithm", "AES256");
// 设置加密使用的密钥，该头域由256-bit的密钥经过base64-encoded得到
headers.put("x-obs-server-side-encryption-customer-key", "your base64 sse-c key generated by AES-256 algorithm");
// 设置加密使用的密钥的MD5值，该头域由密钥的128-bit MD5值经过base64-encoded得到
headers.put("x-obs-server-side-encryption-customer-key-MD5", "the md5 value of your sse-c key");
request.setHeaders(headers);

TemporarySignatureResponse response = obsClient.createTemporarySignature(request);

System.out.println("Getting object using temporary signature url:");
System.out.println("\t" + response.getSignedUrl());
Request.Builder builder = new Request.Builder();
for (Map.Entry<String, String> entry : response.getActualSignedRequestHeaders().entrySet()) {
       builder.header(entry.getKey(), entry.getValue());
}

//使用GET请求下载对象
Request httpRequest = builder.url(response.getSignedUrl()).get().build();
OkHttpClient httpClient = new OkHttpClient.Builder().followRedirects(false).retryOnConnectionFailure(false)
              .cache(null).build();

Call c = httpClient.newCall(httpRequest);
Response res = c.execute();
System.out.println("\tStatus:" + res.code());
if (res.body() != null) {
       System.out.println("\tContent:" + res.body().string() + "\n");
}
res.close();

HttpMethodEnum是OBS Java SDK定义的枚举类型，代表请求方法类型。

加密秘钥的计算方式，可以参考章节：如何生成SSE-C方式的加密秘钥。

父主题： 授权访问

本站部分内容转载于网络，版权归原作者所有，转载之目的在于传播更多优秀技术内容，如有侵权请联系QQ/微信：153890879删除，谢谢！

上一篇：创建存储容量单位包 - 云服务器 ECS 下一篇：没有了

使用URL进行授权访问_对象存储服务 OBS_SDK参考_Java_授权访问

创建桶

上传对象

下载对象

列举对象

删除对象

初始化分段上传任务

上传段

列举已上传段

合并段

获取图片转码的下载链接

下载SSE-C加密类型的对象

推荐图文

你做过代码 Review 吗？

全新开发者体验实验室功能介绍

Oracle Fusion企业绩效管理云，用计划预算管理拥抱

云服务器公网带宽问题 - 常见问题

支持的监控指标_云手机 CPH_用户指南_监控

怎么选择服务器提供商

随机推荐

亮点前瞻 | 中国信通院ICT深度观察报告会

自带光芒！单字符域名i.cn建站爱微商！

一种低延迟的超时中心实现方式

ClickHouse物化视图在微信的实战经验

开发者社区精选直播合集（三）| 企业级安

Redis内存模型

开发者值得关注的9大流行PHP框架

让大型机构的管理和灾备更简单：一云多Re

回溯算法：求组合问题！

新疆喀什疫情｜疫情之下：大数据的洞察力

关于我们