odoo17核心概念—

odoo17核心概念——env

env在odoo中是一个非常重要的概念，它是一个全局变量，保存了odoo运行环境的重要信息，env分为前端和后端

一、环境(env)

1、前端的env

在web\static\src\env.js中定义，包含两个重要的对象：

全局数据总线bus，可以在不同的组件之间进行通信
所有的服务services

这个文件非常重要，它定义了两个函数

makeEnv：初始化env对象。

export function makeEnv() {return {bus: new EventBus(),services: {},debug: odoo.debug,get isSmall() {throw new Error("UI service not initialized!");},};
}

startServices：启动所有的Service，这个函数的实现非常巧妙，因为它要在不考虑服务加载顺序的前提下解决服务之间的依赖问题。其中细节，值得一读。

不过这里只有这两个函数的定义，并没有执行这两个函数，真正执行这两个函数的位置在 start.js中

const env = makeEnv();
await startServices(env);

服务启动完后，会放入env的services对象中。注意其中放的不是服务对象本身，而是start函数的返回值。

2、后端的env

后端的env在odoo\api.py中定义

"""The Odoo API module defines Odoo Environments and method decorators... todo:: Document this module
"""__all__ = ['Environment','Meta','model','constrains', 'depends', 'onchange', 'returns','call_kw',
]

文件的注释中说明了两点：
1、这个文件定义了odoo环境和方法装饰器
2、todo：要为这个模块写文档（啥时候写？）
默认导出的对象，odoo后端最重要的一些对象
‘Environment’,
‘Meta’,
‘model’,
‘constrains’, ‘depends’, ‘onchange’, ‘returns’,
‘call_kw’,

from collections.abc import Mappingclass Environment(Mapping):""" The environment stores various contextual data used by the ORM:- :attr:`cr`: the current database cursor (for database queries);- :attr:`uid`: the current user id (for access rights checks);- :attr:`context`: the current context dictionary (arbitrary metadata);- :attr:`su`: whether in superuser mode.It provides access to the registry by implementing a mapping from modelnames to models. It also holds a cache for records, and a datastructure to manage recomputations."""def reset(self):""" Reset the transaction, see :meth:`Transaction.reset`. """self.transaction.reset()def __new__(cls, cr, uid, context, su=False):if uid == SUPERUSER_ID:su = Trueassert context is not Noneargs = (cr, uid, context, su)# determine transaction objecttransaction = cr.transactionif transaction is None:transaction = cr.transaction = Transaction(Registry(cr.dbname))# if env already exists, return itfor env in transaction.envs:if env.args == args:return env# otherwise create environment, and add it in the setself = object.__new__(cls)args = (cr, uid, frozendict(context), su)self.cr, self.uid, self.context, self.su = self.args = argsself.transaction = self.all = transactionself.registry = transaction.registryself.cache = transaction.cacheself._cache_key = {}                    # memo {field: cache_key}self._protected = transaction.protectedtransaction.envs.add(self)return self

env对象存储了不同类型的上下文数据被ORM使用，
- :attr:cr: the current database cursor (for database queries);
- :attr:uid: the current user id (for access rights checks);
- :attr:context: the current context dictionary (arbitrary metadata);
- :attr:su: whether in superuser mode.

env继承自 collection 的Mapping

在文件的末尾有两句import有点意思

# keep those imports here in order to handle cyclic dependencies correctly
from odoo import SUPERUSER_ID
from odoo.modules.registry import Registry

之所以放在文件末尾，是为了正确的处理循环依赖。姑且先不管的原理是啥了，不过这里引入了一个重要的对象 Regisitry ——后端的注册表

class Registry(Mapping):""" Model registry for a particular database.The registry is essentially a mapping between model names and model classes.There is one registry instance per database."""_lock = threading.RLock()_saved_lock = None@lazy_classpropertydef registries(cls):""" A mapping from database names to registries. """size = config.get('registry_lru_size', None)if not size:# Size the LRU depending of the memory limitsif os.name != 'posix':# cannot specify the memory limit soft on windows...size = 42else:# A registry takes 10MB of memory on average, so we reserve# 10Mb (registry) + 5Mb (working memory) per registryavgsz = 15 * 1024 * 1024size = int(config['limit_memory_soft'] / avgsz)return LRU(size)def __new__(cls, db_name):""" Return the registry for the given database name."""with cls._lock:try:return cls.registries[db_name]except KeyError:return cls.new(db_name)finally:# set db tracker - cleaned up at the WSGI dispatching phase in# odoo.http.rootthreading.current_thread().dbname = db_name