# atomic() 方法 
# from django.db import transaction
###################
# atomic()
###################
def atomic(using=None, savepoint=True): # 裝飾器和上下文管理器必須.()調(diào)用方法，因?yàn)檎嬲奶幚硎窃摲椒ǚ祷氐膶?shí)例，不是該方法本身
 if callable(using):
  return Atomic(DEFAULT_DB_ALIAS, savepoint)(using)
 # Decorator: @atomic(...) or context manager: with atomic(...): ...
 else:
  return Atomic(using, savepoint)
##########################################
# Atomic類 省略了非核心內(nèi)容
############################################
class Atomic(ContextDecorator):
 def __init__(self, using, savepoint):
 self.using = using
 self.savepoint = savepoint
 def __enter__(self):
 connection = get_connection(self.using)
 sid = connection.savepoint()   # 進(jìn)入with創(chuàng)建一個(gè)保存點(diǎn)
 # .............do
 def __exit__(self, exc_type, exc_value, traceback):
 if connection.in_atomic_block:
 # do.............
 if sid is not None:
  try:
   connection.savepoint_commit(sid)  # 提交事務(wù)
  except DatabaseError:
   try:
    connection.savepoint_rollback(sid) # 捕獲數(shù)據(jù)庫(kù)異?；貪L
    connection.savepoint_commit(sid)
   except Error:
    connection.needs_rollback = True
   raise
 ## 還有一段代碼是exec_type收到其他程序異常時(shí)候 全局回滾，此處省略
 # do.................
###############################
# ContextDecorator
#################################
class ContextDecorator(object):
 def __call__(self, func):
  def inner(*args, **kwargs):
   with self:    # 把函數(shù)放進(jìn)self的with上下文管理器，效果with相同，只是控制細(xì)粒度不同
    return func(*args, **kwargs)
  return inner

class Tran():
 def __init__(self, conn=None, close=True):
  if conn is None:     # 創(chuàng)建數(shù)據(jù)庫(kù)鏈接
   print 'init'
   self.conn = conn_tbkt()
   self.cur = self.conn.cursor()
   self.sql = []

 def __enter__(self):       # 上下文管理器返回 sql語(yǔ)句列表 with Tran('tbkt_pxb') as sqls:
  print 'enter'
  return self.sql  # sql.append('select 1')

 def __exit__(self, exc_type, exc_val, exc_tb):
  print 'exit'
  try:

   print self.sql        # 執(zhí)行sql
   for s in self.sql:
    self.cur.execute(s)
   self.conn.commit()
  except:            # 可以捕獲所有異常(django事務(wù)如果中間出現(xiàn)程序異常終止無(wú)法回滾)
   try:     # 回滾本身也是sql執(zhí)行，也有可能失敗
    import traceback
    traceback.print_exc()
    print 'rollback'
    self.conn.rollback()
   except:
    print u'回滾失敗'
  finally:
   self.cur.close()
   self.conn.close()

# 在事務(wù)塊中@atomic() 或者 with atomic():
sid = transaction.savepoint('tbkt_pxb')
try:
 # do ..........
except:
 transaction.savepoint_rollback(sid, 'tbkt_pxb')

  ziyuan_app = ['math2', 'ziyuan']
  if model._meta.app_label in ziyuan_app:
   return "ziyuan_new"

  return 'default'