[Python] SQLBuilder 演示样例代码

Posted 2020-09-16

用Python写一个SQLBuilder。Java版能够从 http://www.java2s.com/Code/Java/Database-SQL-JDBC/SQLBuilder.htm 看到。

附上代码：

演示样例代码（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。

代码演示样例（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()

演示样例代码（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()