JayDeBeApi 触发 java.sql.SQLException：找不到合适的驱动程序

Question

我正在尝试使用JayDeBeApi包在Python 3 中连接到Teradata数据库。这是使用Flask和Flask-Restplus的 API 项目的一部分

这是重现该问题的最小工作示例。在终端窗口中，键入以下命令来设置您的工作站：

# Install JVM
sudo apt-get install default-jre

# Create Python virtual environment
sudo apt-get install python3-venv
python3 -m venv jdbc
source jdbc/bin/activate

# Install Python packages in virtual environment
pip3 install --upgrade pip
pip3 install jaydebeapi
pip3 install flask

使用以下内容创建文件 app.py：

from flask import Flask
import jaydebeapi

app = Flask(__name__)


def get_jdbc_connection():
    connection = jaydebeapi.connect(
        'com.teradata.jdbc.TeraDriver',
        'jdbc:teradata://edw-dev.company.org',
        {'user': 'LOGIN', 'password': 'PASSWORD', 'tmode': 'TERA', 'charset': 'UTF8'},
        '/home/alexis/teradataDriverJdbc.jar')
    return connection


@app.route('/hello/')
def hello_world():
    print('Init second connection')
    get_jdbc_connection()
    print('Success')
    return 'Hello world!'


if __name__ == '__main__':
    print('Init connection')
    test_connection = get_jdbc_connection()
    test_connection.close()
    print('Init connection closed')
    app.run(host='localhost', port=5000, threaded=True, debug=True)

在激活虚拟环境的终端窗口中，键入以下内容：

python3
>>> import app
>>> app.get_jdbc_connection()
<jaydebeapi.Connection object at 0x7f28ecb2ebe0>

上面的代码片段有效并且该方法get_jdbc_connection()返回一个连接对象。现在尝试用 Flask 运行它。在激活虚拟环境的终端窗口中，键入以下内容：

python3 app.py
Init connection
Init connection closed
 * Running on http://localhost:5000/ (Press CTRL+C to quit)
 * Restarting with stat
Init connection
Init connection closed
 * Debugger is active!
 * Debugger PIN: 301-429-987

在您的浏览器中，导航到http://localhost:5000/hello/ 您将收到以下错误消息，这与我在上面的第一条消息中粘贴的错误消息相同：

Init second connection
127.0.0.1 - - [08/Mar/2018 16:00:30] "GET /hello/ HTTP/1.1" 500 -
Traceback (most recent call last):
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/app.py", line 2000, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/app.py", line 1991, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/app.py", line 1567, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/_compat.py", line 33, in reraise
    raise value
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/app.py", line 1988, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/app.py", line 1641, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/app.py", line 1544, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/_compat.py", line 33, in reraise
    raise value
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/app.py", line 1639, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/alexis/dq/lib/python3.5/site-packages/flask/app.py", line 1625, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/alexis/app.py", line 19, in hello_world
    get_jdbc_connection()
  File "/home/alexis/app.py", line 12, in get_jdbc_connection
    '/home/alexis/teradataDriverJdbc.jar')
  File "/home/alexis/dq/lib/python3.5/site-packages/jaydebeapi/__init__.py", line 381, in connect
    jconn = _jdbc_connect(jclassname, url, driver_args, jars, libs)
  File "/home/alexis/dq/lib/python3.5/site-packages/jaydebeapi/__init__.py", line 199, in _jdbc_connect_jpype
    return jpype.java.sql.DriverManager.getConnection(url, *dargs)
jpype._jexception.java.sql.SQLExceptionPyRaisable: java.sql.SQLException: No suitable driver found for jdbc:teradata://edw-dev.company.org

备注：我也在 Github 项目上创建了一个 issue：https : //github.com/baztian/jaydebeapi/issues/66

编辑：根据 baztian 的推荐，我在 jPype Github 项目上提出了这个问题：https : //github.com/originell/jpype/issues/290

Answer 1

可以解决您的问题的解决方法如下：

   def get_jdbc_connection():
        import jpype
        if jpype.isJVMStarted() and not jpype.isThreadAttachedToJVM():
            jpype.attachThreadToJVM()
            jpype.java.lang.Thread.currentThread().setContextClassLoader(jpype.java.lang.ClassLoader.getSystemClassLoader())
        connection = jaydebeapi.connect(
            'com.teradata.jdbc.TeraDriver',
            'jdbc:teradata://edw-dev.company.org',
            {'user': 'LOGIN', 'password': 'PASSWORD', 'tmode': 'TERA', 'charset': 'UTF8'},
            '/home/alexis/teradataDriverJdbc.jar')
        return connection