**文件管理**
##############################

在NOS中，用户可以通过一系列的接口管理桶(Bucket)中的文件(Object)，比如list_objects，delete_object，copy_object等。

列出桶中的文件
=============================

您可以使用list_objects列出桶中的文件::

    import boto3
    import botocore

    access_key = "您的accessKeyId"
    secret_key = "您的accessKeySecret"
    end_point  = "建桶时选择的的区域域名"
    s3Client = boto3.client('s3',aws_access_key_id=access_key,aws_secret_access_key=secret_key,endpoint_url=end_point,)

    try:
        object_lists = s3Client.list_objects(Bucket=bucketName)
        for ob in object_lists['Contents']:
            print("key : {0}".format(ob["Key"]))
    except botocore.exceptions.ClientError as e:
        print(
            "ServiceError: %s\n"
            "status_code: %s\n"
            "error_code: %s\n"
            "request_id: %s\n"
            "message: %s\n" % (
            e,
            e.response['ResponseMetadata']['HTTPStatusCode'],  # 错误http状态码
            e.response["Error"]['Code'],  # NOS服务器定义错误类型
            e.response['ResponseMetadata']['HTTPHeaders']['x-nos-request-id'],  # NOS服务器定义错误码
            e.response['Error']['Message'],  # 请求ID，有利于nos开发人员跟踪异常请求的错误原因
        ))
    except botocore.exceptions.ParamValidationError as e:
        print(
            "ClientError: %s\n"
            "message: %s\n"
            % (
                e,
                e.fmt
            ))
    

list_objects可以指定的可选参数如下所示:

+------------------------+---------------------------------------------------------------------------------------------------------+
|参数                    |    说明                                                                                                 |
+========================+=========================================================================================================+
| delimiter              |用于对Object名字进行分组的字符。所有名字包含指定的前缀且第一次出现delimiter字符之间的object作为一组元素  |
+------------------------+---------------------------------------------------------------------------------------------------------+
| prefix                 |限定返回的object key必须以prefix作为前缀。注意使用prefix查询时，返回的key中仍会包含prefix                |
+------------------------+---------------------------------------------------------------------------------------------------------+
| limit                  |限定此次返回object的最大数，如果不设定，默认为100                                                        |
+------------------------+---------------------------------------------------------------------------------------------------------+
| marker                 |设定结果从marker之后按字母排序的第一个开始返回                                                           |
+------------------------+---------------------------------------------------------------------------------------------------------+

删除单个文件
===========================

您可以使用delete_object删除单个需要删除的文件::

    import boto3
    import botocore

    try:
        s3Client.delete_object(bucket, object)
    except botocore.exceptions.ClientError as e:
        print(
            "ServiceError: %s\n"
            "status_code: %s\n"
            "error_code: %s\n"
            "request_id: %s\n"
            "message: %s\n" % (
            e,
            e.response['ResponseMetadata']['HTTPStatusCode'],  # 错误http状态码
            e.response["Error"]['Code'],  # NOS服务器定义错误类型
            e.response['ResponseMetadata']['HTTPHeaders']['x-nos-request-id'],  # NOS服务器定义错误码
            e.response['Error']['Message'],  # 请求ID，有利于nos开发人员跟踪异常请求的错误原因    
        ))
    except botocore.exceptions.ParamValidationError as e:
        print(
            "ClientError: %s\n"
            "message: %s\n"
            % (
                e,
                e.fmt
            ))

删除多个文件
============================
您可以使用delete_objects批量删除文件::

    import boto3
    import botocore

    keys = {
            'Objects': [
                {
                    'Key': 'string',
                },
                {
                    'Key': 'aa'
                },
                {
                    'Key': key
                }
            ],
            'Quiet': True
        }
    #如果Quiet=True，那么正确删除的将不显示，反之会显示

    try:
        client.delete_objects(bucket, keys)
    except botocore.exceptions.ClientError as e:
        print(
            "ServiceError: %s\n"
            "status_code: %s\n"
            "error_code: %s\n"
            "request_id: %s\n"
            "message: %s\n" % (
            e,
            e.response['ResponseMetadata']['HTTPStatusCode'],  # 错误http状态码
            e.response["Error"]['Code'],  # NOS服务器定义错误类型
            e.response['ResponseMetadata']['HTTPHeaders']['x-nos-request-id'],  # NOS服务器定义错误码
            e.response['Error']['Message'],  # 请求ID，有利于nos开发人员跟踪异常请求的错误原因
        ))
    except botocore.exceptions.ParamValidationError as e:
        print(
            "ClientError: %s\n"
            "message: %s\n"
            % (
                e,
                e.fmt
            ))

拷贝文件
===========================

您可以使用copy_object拷贝文件::

    import boto3
    import botocore

    try:
        copySource = "/{0}/{1}".format(bucketName, key) #格式按照这个来，否者NOS不接受该请求
        response = s3Client.copy_object(CopySource=copySource, Bucket=destBucketName, Key=destKey)
    except botocore.exceptions.ClientError as e:
        print(
            "ServiceError: %s\n"
            "status_code: %s\n"
            "error_code: %s\n"
            "request_id: %s\n"
            "message: %s\n"
            % (
            e,
            e.response['ResponseMetadata']['HTTPStatusCode'],  # 错误http状态码
            e.response["Error"]['Code'],  # NOS服务器定义错误类型
            e.response['ResponseMetadata']['HTTPHeaders']['x-nos-request-id'],  # NOS服务器定义错误码
            e.response['Error']['Message'],  # 请求ID，有利于nos开发人员跟踪异常请求的错误原因
        ))
    except botocore.exceptions.ParamValidationError as e:
        print(
            "ClientError: %s\n"
            "message: %s\n"
            % (
                e,
                e.fmt
            ))

.. attention::

    1. 支持跨桶的文件copy




生成私有对象可下载的URL链接
===========================    

您可以使用generate_presigned_url来生成私有对象的可下载的URL::


    url = s3Client.generate_presigned_url(
        ClientMethod='get_object',
        Params={
            'Bucket': bucketName,
            'Key': objectName
        },
        ExpiresIn = 10 # 单位s，默认3600s
    )
    print(url) # print的内容是可以直接用来下载对象的，可以直接贴到浏览器中下载