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# 第 2 步：测试与分类账的连接
**重要**
终止支持通知：现有客户将能够使用 Amazon QLDB，直到 2025 年 7 月 31 日终止支持。有关更多详细信息，请参阅[将亚马逊 QLDB 账本迁移到亚马逊 Aurora PostgreSQL](https://aws.amazon.com/blogs/database/migrate-an-amazon-qldb-ledger-to-amazon-aurora-postgresql/)。
在此步骤中，您将验证是否可以使用事务数据 API 端点连接至 Amazon QLDB 中的`vehicle-registration`分类账。
**测试与分类账的连接**
1. 查看以下程序（`connect_to_ledger.py`），该程序创建了与 `vehicle-registration` 分类账的数据会话连接。
------
#### [ 3.x ]
```
# Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: MIT-0
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of this
# software and associated documentation files (the "Software"), to deal in the Software
# without restriction, including without limitation the rights to use, copy, modify,
# merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
# PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# This code expects that you have AWS credentials setup per:
# https://boto3.amazonaws.com/v1/documentation/api/latest/guide/quickstart.html
from logging import basicConfig, getLogger, INFO
from botocore.exceptions import ClientError
from pyqldb.driver.qldb_driver import QldbDriver
from pyqldbsamples.constants import Constants
logger = getLogger(__name__)
basicConfig(level=INFO)
def create_qldb_driver(ledger_name=Constants.LEDGER_NAME, region_name=None, endpoint_url=None, boto3_session=None):
"""
Create a QLDB driver for executing transactions.
:type ledger_name: str
:param ledger_name: The QLDB ledger name.
:type region_name: str
:param region_name: See [1].
:type endpoint_url: str
:param endpoint_url: See [1].
:type boto3_session: :py:class:`boto3.session.Session`
:param boto3_session: The boto3 session to create the client with (see [1]).
:rtype: :py:class:`pyqldb.driver.qldb_driver.QldbDriver`
:return: A QLDB driver object.
[1]: `Boto3 Session.client Reference `.
"""
qldb_driver = QldbDriver(ledger_name=ledger_name, region_name=region_name, endpoint_url=endpoint_url,
boto3_session=boto3_session)
return qldb_driver
def main(ledger_name=Constants.LEDGER_NAME):
"""
Connect to a given ledger using default settings.
"""
try:
with create_qldb_driver(ledger_name) as driver:
logger.info('Listing table names ')
for table in driver.list_tables():
logger.info(table)
except ClientError as ce:
logger.exception('Unable to list tables.')
raise ce
if __name__ == '__main__':
main()
```
**注意**
要在分类账上运行数据事务，必须创建一个 QLDB 驱动对象以连接到指定的分类账。这与您在上一步中创建分类账时使用的 `qldb_client` 客户端对象不同。之前的客户端仅用于[Amazon QLDB API 参考](api-reference.md)中列出的管理 API 操作。
创建此驱动程序对象时，您必须指定分类账名称。
------
#### [ 2.x ]
```
# Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: MIT-0
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of this
# software and associated documentation files (the "Software"), to deal in the Software
# without restriction, including without limitation the rights to use, copy, modify,
# merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
# PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# This code expects that you have AWS credentials setup per:
# https://boto3.amazonaws.com/v1/documentation/api/latest/guide/quickstart.html
from logging import basicConfig, getLogger, INFO
from botocore.exceptions import ClientError
from pyqldb.driver.pooled_qldb_driver import PooledQldbDriver
from pyqldbsamples.constants import Constants
logger = getLogger(__name__)
basicConfig(level=INFO)
def create_qldb_driver(ledger_name=Constants.LEDGER_NAME, region_name=None, endpoint_url=None, boto3_session=None):
"""
Create a QLDB driver for creating sessions.
:type ledger_name: str
:param ledger_name: The QLDB ledger name.
:type region_name: str
:param region_name: See [1].
:type endpoint_url: str
:param endpoint_url: See [1].
:type boto3_session: :py:class:`boto3.session.Session`
:param boto3_session: The boto3 session to create the client with (see [1]).
:rtype: :py:class:`pyqldb.driver.pooled_qldb_driver.PooledQldbDriver`
:return: A pooled QLDB driver object.
[1]: `Boto3 Session.client Reference `.
"""
qldb_driver = PooledQldbDriver(ledger_name=ledger_name, region_name=region_name, endpoint_url=endpoint_url,
boto3_session=boto3_session)
return qldb_driver
def create_qldb_session():
"""
Retrieve a QLDB session object.
:rtype: :py:class:`pyqldb.session.pooled_qldb_session.PooledQldbSession`
:return: A pooled QLDB session object.
"""
qldb_session = pooled_qldb_driver.get_session()
return qldb_session
pooled_qldb_driver = create_qldb_driver()
if __name__ == '__main__':
"""
Connect to a session for a given ledger using default settings.
"""
try:
qldb_session = create_qldb_session()
logger.info('Listing table names ')
for table in qldb_session.list_tables():
logger.info(table)
except ClientError:
logger.exception('Unable to create session.')
```
**注意**
要在分类账上运行数据事务，必须创建一个 QLDB 驱动程序对象以连接到指定的分类账。这与您在上一步中创建分类账时使用的 `qldb_client` 客户端对象不同。此前的客户端仅用于[Amazon QLDB API 参考](api-reference.md)中列出的管理 API 操作。
首先，创建一个池化的 QLDB 驱动程序对象。创建此驱动程序时，您必须指定分类账名称。
然后，您可以从此池驱动程序对象创建会话。
------
1. 要运行该程序，请输入以下命令。
```
python connect_to_ledger.py
```
要在 `vehicle-registration` 分类账中创建表，请继续 [步骤 3：创建表、索引与示例数据](getting-started.python.step-3.md)。