[Python] SQLBuilder 示例代码
用Python写一个SQLBuilder，Java版可以从 http://www.java2s.com/Code/Java/Database-SQL-JDBC/SQLBuilder.htm 看到。
附上代码：
示例代码（一）：
class SQLDirector:
@classmethod
def buildSQL(cls, builder):
sql = ""
sql += builder.getCommand()
sql += builder.getTable()
sql += builder.getWhat()
sql += builder.getCriteria()
return sql
class SQLBuilder:
def __init__(self): pass
def __del__(self): pass
def getCommand(self): pass
def getTable(self): pass
def getWhat(self): pass
def getCriteria(self): pass
class InsertBuilder(SQLBuilder):
def __init__(self):
self._table = ""
self._columnsAndData = dict()
self._criteria = ""
def setTable(self, table):
self._table = table
def getCommand(self):
return "INSERT INTO "
def getTable(self):
return self._table
def getWhat(self):
columns = list()
values = list()
what = ""
for columnName in self._columnsAndData:
columns.append(columnName)
values.append(self._columnsAndData[columnName])
columns_str = string.join( map(lambda x: str(x), columns), "," )
values_str = string.join( map(lambda x: str(x), values), "," )
what += " ("
what += columns_str
what += ") VALUES ("
what += values_str
what += ") "
return what
def getCriteria(self):
return ""
def addColumnAndData(self, columnName, value):
if value:
self._columnsAndData[columnName] = value
def main():
builder = InsertBuilder()
builder.setTable("employees")
builder.addColumnAndData("employee_id", int(221))
builder.addColumnAndData("first_name", "'Shane'")
builder.addColumnAndData("last_name", "'Grinnell'")
builder.addColumnAndData("email", "'[email protected]'")
sql = SQLDirector.buildSQL(builder)
print sql
if __name__ == '__main__':
main()
更有意思的玩法，
代码示例（二）：
#!/usr/bin/env python
import string
class SQLDirector:
def __init__(self, builder):
self._builder = builder
def construct(self):
self._builder.buildSQL()
return self._builder.getSQL()
class SQLBuilder:
def __init__(self): self._sql = ''
def buildSQL(self): return self
def getSQL(self): return self._sql
class InsertBuilder(SQLBuilder):
def __init__(self):
self._columns = list()
self._values = list()
def buildSQL(self):
columns_str = string.join( map(lambda x: "`%s`" % str(x), self._columns), "," )
values_str = string.join( map(lambda x: "'%s'" % str(x), self._values), "," )
self._sql = "INSERT INTO "
self._sql += self._table
self._sql += " (%s) VALUES (%s) " % (columns_str, values_str)
return self
def table(self, table):
self._table = table
return self
def column(self, columnName, value):
self._columns.append(columnName)
self._values.append(value)
return self
def main():
insertBuilder = InsertBuilder()
insertBuilder.table("dt_process") \
.column("attr_key","foo").column("attr_val", "bar")
sqlDirector = SQLDirector(insertBuilder)
print sqlDirector.construct()
if __name__ == "__main__":
main()
示例代码（三）：
#!/usr/bin/env python
import string
def main():
insertBuilder = InsertBuilder()
insertBuilder.table("dt_process") \
.column("attr_key","foo").column("attr_val", "bar")
sqlDirector = SQLDirector(insertBuilder)
print sqlDirector.construct()
createBuilder = CreateBuilder()
createBuilder.table("newTable").ifnotexists() \
.column("id").col_type("INTEGER").col_autoincrement() \
.column("name").col_type("VARCHAR(40)").col_nullable(False).col_default("empty")
sqlDirector = SQLDirector(createBuilder)
print sqlDirector.construct()
# -----------------------------------------------------------------------------
# Libraries
# -----------------------------------------------------------------------------
class SQLDirector:
def __init__(self, builder):
self._builder = builder
def construct(self):
self._builder.buildSQL()
return self._builder.getSQL()
class SQLBuilder:
def __init__(self): self._sql = ''
def buildSQL(self): return self
def getSQL(self): return self._sql
class CreateBuilder(SQLBuilder):
def __init__(self):
self._columns = list() # item: dict => 'name', 'nullable', 'default'
self._column_context = None
self._table = ""
self._ifnotexists = ""
self._criteria = ""
def _map_column(self, column):
sql = ""
if column.has_key('name'): sql += " `%s`"%column['name']
if column.has_key('type'): sql += " %s"%column['type']
if column.has_key('nullable'): sql += "%s"%column['nullable']
if column.has_key('default'): sql += "%s"%column['default']
if column.has_key('auto_increment'): sql += "%s"%column['auto_increment']
return sql
def _reduce_column(self, left, right):
return left + ", " + right
def buildSQL(self):
columns_str = reduce(self._reduce_column, map( self._map_column, self._columns ))
self._sql = "CREATE TABLE "
self._sql += self._ifnotexists
self._sql += self._table
self._sql += " (%s)" % columns_str
return self
def ifnotexists(self):
self._ifnotexists = " IF NOT EXISTS "
return self
def table(self, table):
self._table = table
return self
def column(self, columnName):
column = dict()
column['name'] = columnName
self._columns.append(column)
self._column_context = column
return self
def col_type(self, type):
self._column_context['type'] = type
return self
def col_nullable(self, nullable=True):
if nullable:
self._column_context['nullable'] = ""
else:
self._column_context['nullable'] = " NOT NULL"
return self
def col_default(self, default):
self._column_context['default'] = " DEFAULT %s" % default
return self
def col_autoincrement(self, autoincrement=True):
self._column_context['auto_increment'] = " AUTO_INCREMENT"
return self
def primary(self, primary=True):
self._primary_key.append(self._column_context['name'])
return self
#
# INSERT INTO
#
class InsertBuilder(SQLBuilder):
def __init__(self):
self._columns = list()
self._values = list()
self._table = ""
def buildSQL(self):
columns_str = string.join( map(lambda x: "`%s`" % str(x), self._columns), "," )
values_str = string.join( map(lambda x: "'%s'" % str(x), self._values), "," )
self._sql = "INSERT INTO "
self._sql += self._table
self._sql += " (%s) VALUES (%s) " % (columns_str, values_str)
return self
def table(self, table):
self._table = table
return self
def column(self, columnName, value):
self._columns.append(columnName)
self._values.append(value)
return self
if __name__ == "__main__":
main()