collective.lead 1.0

用例

• You want SQLAlchemy
• You want to look up database connections/sessions as named utilities
• You want to use simple domain/mapper classes, with no particular dependencies
• You don’t want to worry about transaction and connection handling
• You want to be able to configure SQL connection parameters at run-time, e.g. in the ZODB. Well, you don’t have to, but it’s nice to have the option.

你要做什么

假设我们有一些域类tableone和table2，与表相关 表1和表2。

>>> class TableOne(object):
...     pass
>>> class TableTwo(object):
...     pass

您应该将collective.lead.database子类化，填写它的模板 方法，然后将新类注册为全局的、非持久的 提供IDatabase的命名实用程序。

>>> from collective.lead import Database
>>> import sqlalchemy as sa

>>> class MyDatabase(Database):
...     @property
...     def _url(self):
...         return sa.engine.url.URL(drivername='mysql', username='user',
...                    host='localhost',  database='testdb')
...
...     def _setup_tables(self, metadata, tables):
...         tables['table1'] = sa.Table('table1', metadata, autoload=True)
...         tables['table2'] = sa.Table('table2', metadata, autoload=True)
...
...     def _setup_mappers(self, tables, mappers):
...         mappers['table1'] = sa.mapper(TableOne, tables['table1'])
...         mappers['table2'] = sa.mapper(TableTwo, tables['table2'],
...                                         properties = {
...                                             'table1' : sa.relation(TableOne),
...                                             })

现在可以使用zcml注册数据库实用程序：

<utility

provides=”collective.lead.interfaces.IDatabase” factory=”.database.MyDatabase” name=”my.database” />

或者如果您喜欢直接从python（xxx，这不起作用）：

>>> from zope.component import provideUtility
>>> from collective.lead.interfaces import IDatabase
>>> provideUtility(MyDatabase, name='my.database', provides=IDatabase)

使用数据库连接

在应用程序代码中，现在可以按名称获取数据库引擎。这个引擎 是线程本地的，并且包含单个缓存会话。当它第一次 请求时，将开始新的交易。这是连接到zope的 事务，并在请求时根据需要提交或回滚 末端。或者，换言之，它应该或多或少地像你期望的那样工作 您不必担心事务（无论是zope还是sql事务）。

>>> from zope.component import getUtility
>>> db = getUtility(IDatabase, name='my.database')
>>> db.session.query(TableOne).list()
[]

>>> db.connection.execute("SELECT * FROM table1")