一个简单的Python MVC框架(2)

框架(2)"/>

一个简单的Python MVC框架(2)

import pymysql
import os
#用于测试
class EmptyModel:def __init__(self,name=None):self.TableName=name
#数据库帮助基类，相当于接口。其实对于python这种语言，这个类完全没必要存在.
#不过对于多种数据库支持时，还是有点用.
#注意：这里的参数是格式化到字符串，无法防止SQL注入。为了防止SQL注入，可以对SQL进行处理。
#一般来说最好的办法是真正参数化，但我看了一下pymysql,并没有提供真正参数化的方法。
class DbHelper:def QueryByParam(self,sql,pms,EntityName,conn=None):return []def ExecuteCommand(self,sql,pms,conn=None):return 0
#Mysql的访问类，基于pymysql.
class DbHelperMySql(DbHelper):def __init__(self,CharsetName='utf8'):self.CharsetName = CharsetNameif(self.CharsetName==''):self.CharsetName='utf8'def ExecuteCommand(self,sql,pms,conn=None):theNeedCloseConn = Falseif(conn==None):conn=self.GetMySqlDbConnDefault()theNeedCloseConn = TruetheCursor = conn.cursor()try:theCursor.execute("set NAMES "+self.CharsetName) #保证字符集正确.theRet = theCursor.execute(sql,pms)finally:theCursor.close()if theNeedCloseConn:conn.close()return theRet@staticmethoddef GetMySqlDbConn(host,port,user,pwd,dbname):return pymysql.connect(host=host, port=port,user=user, passwd=pwd, db=dbname)@staticmethoddef GetMySqlDbConnDefault():return DbHelperMySql.GetMySqlDbConn('127.0.0.1',3306,'xxxxx','xxxxx','dbname')#pms 为Dict类型.def QueryByParam1(self,sql,pms,EntityName,conn=None):theNeedCloseConn = Falseif(conn==None):conn=self.GetMySqlDbConnDefault()theNeedCloseConn = TruetheCursor = conn.cursor(pymysql.cursors.DictCursor)try:theCursor.execute("set NAMES "+self.CharsetName) #保证字符集正确.theCursor.execute(sql,pms)rows = theCursor.fetchall()models=[]for r in rows:m=EmptyModel(EntityName)for fld in r.items():setattr(m,fld[0],fld[1])models.append(m)return modelsfinally:theCursor.close()if theNeedCloseConn:conn.close()return []#pms 为Dict类型.def QueryByParam2(self,EntityType,sql,pms,conn=None):theNeedCloseConn = Falseif(conn==None):conn=self.GetMySqlDbConnDefault()theNeedCloseConn = TruetheCursor = conn.cursor(pymysql.cursors.DictCursor)try:theCursor.execute("set NAMES "+self.CharsetName) #保证字符集正确.theCursor.execute(sql,pms)rows = theCursor.fetchall()models=[]for r in rows:m=EntityType()for fld in r.items():setattr(m,fld[0],fld[1])m.CurrFields.append(fld[0])models.append(m)return modelsfinally:theCursor.close()if theNeedCloseConn:conn.close()return []

没有单独做一个数据访问层，实体访问就放在业务基类中：
3）业务层基类：
主要提供实体类的增加，修改，删除和查询（单个和List),现在的应用模式，一般情况下不要缓存实体。EF和Hibernate那种缓存，其实都是灾难的开始。给实体打状态编辑，也仅仅是为了处理前面传过来的实体集合可以分解成增加，修改和删除。除此之外，实体状态的维护也是没必要的。

from DbOpts import *
import uuid
class BusinessBase(object):def __init__(self,EntityType):self.EntityType = EntityTypedef AddModel(self,model,conn=None):theDb=DbHelperMySql()theInsertSQL=model.GetInsertSQL()theValues=[]theFields = model.GetFields()for theF in theFields:theValues.append(model[theF])theRet= theDb.ExecuteCommand(theInsertSQL,theValues,conn)return theRetdef GetModels(self,sql,pms,conn=None):theDb=DbHelperMySql()return theDb.QueryByParam2(self.EntityType,sql,pms,conn)def GetModel(self,pk,conn=None):theTable = self.EntityType.TableNametheKeyField=self.EntityType.KeyFieldtheSQL = 'SELECT * FROM '+theTable+' WHERE '+theKeyField+'='+self.EntityType.FieldParams[theKeyField]['DSFmt']theParam=(pk)theModels = self.GetModels(theSQL,theParam,conn)if len(theModels)>0:return theModels[0]return Nonedef UpdateModel(self,model,conn=None):theDb=DbHelperMySql()theSQL=model.GetUpdateAllSQL()theValues=[]theFields = model.GetFields()for theF in theFields:theValues.append(model[theF])theRet= theDb.ExecuteCommand(theSQL,theValues,conn)return theRet@staticmethoddef GetGuid():return uuid.uuid1().__str__()def GetDbTables(self,dbname,conn=None):theSQL='select table_Comment as Script, table_Name as TableName,table_Type from INFORMATION_SCHEMA.tables where 1=1'if(dbname!=None and dbname !=''):theSQL += ' and table_schema=\''+dbname+'\''theDb=DbHelperMySql()return theDb.QueryByParam1(theSQL,None,'tables',conn)def GetTabFields(self,dbname,tablename,conn=None):theSQL ='select a.table_name,a.column_name,a.data_type,a.is_nullable,\a.character_maximum_length as maxlengthb,a.character_octet_length as lengthb,\a.numeric_precision as precisionlen,a.numeric_scale as scalelen, \b.iskey \from information_schema.columns as a \left join ( select t.TABLE_NAME,c.COLUMN_NAME,1 as iskey from \INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS t,  INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS c \WHERE  t.TABLE_NAME = c.TABLE_NAME  AND t.CONSTRAINT_TYPE = \'PRIMARY KEY\' ) as b \on a.table_name =b.table_name and a.column_name=b.column_name \where 1=1'if(dbname!=None and dbname !=''):theSQL += ' and a.table_schema=\''+dbname+'\''if(tablename!=None and tablename !=''):theSQL += ' and a.table_name=\''+tablename+'\''theDb=DbHelperMySql()return theDb.QueryByParam1(theSQL,None,'columns',conn)

我在基本方法中增加了conn参数，目的是为了扩展后面的事务处理。对于分布式的事务，这种方法是不适合的，但也只需要定义一个自己的事务类，这个事务包含参与事务的连接即可。