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Python设计模式:适配器与外观

2026-07-01 14:23:49

Python设计模式:适配器与外观

副标题

: 90%的人不知道，适配器模式能让不兼容的接口协同工作

痛点：为什么你的第三方库总是难以集成？

2025年某项目需要集成3个不同的支付API，每个API的接口都不一样。问题出在哪？工程师没有使用适配器模式统一接口。

真相

：适配器模式让接口不兼容的类可以一起工作。

模式	核心目的	典型场景
适配器	接口转换	第三方库集成、遗留代码
外观	简化接口	复杂子系统访问

一、适配器模式

1.1 什么是适配器模式

将一个类的接口转换成客户希望的另一个接口。

# 目标接口（客户期望的）
class PaymentProcessor:
def process_payment(self, amount):
pass
需要适配的类（不兼容的）
class LegacyPaymentGateway:
def make_payment(self, money):
print(f"旧网关支付: ${money}")
return True
def refund_payment(self, money):
print(f"旧网关退款: ${money}")
return True
类适配器（多重继承）
class LegacyPaymentAdapter(PaymentProcessor, LegacyPaymentGateway):
def process_payment(self, amount):
return self.make_payment(amount)
def refund(self, amount):
return self.refund_payment(amount)
对象适配器（组合）
class PaymentGatewayAdapter(PaymentProcessor):
def __init__(self, legacy_gateway):
self._gateway = legacy_gateway
def process_payment(self, amount):
return self._gateway.make_payment(amount)
def refund(self, amount):
return self._gateway.refund_payment(amount)
使用
legacy = LegacyPaymentGateway()
adapter = PaymentGatewayAdapter(legacy)
adapter.process_payment(100)

1.2 适配器模式vs桥接模式

# 适配器：改变接口
class Target:
def request(self):
pass
class Adaptee:
def specific_request(self):
pass
class Adapter(Target):
def __init__(self, adaptee):
self._adaptee = adaptee
def request(self):
self._adaptee.specific_request()
桥接：分离抽象和实现
class Implementor:
def operation(self):
pass
class RefinedImplementorA(Implementor):
def operation(self):
return "实现A"
class RefinedImplementorB(Implementor):
def operation(self):
return "实现B"
class Abstraction:
def __init__(self, implementor):
self._implementor = implementor
def operation(self):
return self._implementor.operation()
class RefinedAbstraction(Abstraction):
def extended_operation(self):
return self.operation() + " 扩展"

1.3 真实场景：数据库适配器

# 统一的数据库接口
class Database:
def connect(self):
pass
def query(self, sql):
pass
def close(self):
pass
MySQL适配器
class MySQLAdapter(Database):
def __init__(self, host, user, password):
self.host = host
self.user = user
self.password = password
self._conn = None
def connect(self):
import pymysql
self._conn = pymysql.connect(
host=self.host,
user=self.user,
password=self.password
)
print(f"连接 MySQL: {self.host}")
def query(self, sql):
if not self._conn:
raise RuntimeError("未连接")
with self._conn.cursor() as cursor:
cursor.execute(sql)
return cursor.fetchall()
def close(self):
if self._conn:
self._conn.close()
PostgreSQL适配器
class PostgreSQLAdapter(Database):
def __init__(self, host, user, password, database):
self.host = host
self.user = user
self.password = password
self.database = database
self._conn = None
def connect(self):
import psycopg2
self._conn = psycopg2.connect(
host=self.host,
user=self.user,
password=self.password,
database=self.database
)
print(f"连接 PostgreSQL: {self.host}")
def query(self, sql):
if not self._conn:
raise RuntimeError("未连接")
with self._conn.cursor() as cursor:
cursor.execute(sql)
return cursor.fetchall()
def close(self):
if self._conn:
self._conn.close()
使用
db = MySQLAdapter("localhost", "user", "pass")
db.connect()
results = db.query("SELECT * FROM users")
db.close()

二、外观模式

2.1 什么是外观模式

为子系统中的一组接口提供一个一致的界面。

# 子系统类
class CPU:
def freeze(self):
print("CPU: 冻结")
def jump(self, position):
print(f"CPU: 跳转到 {position}")
def execute(self):
print("CPU: 执行")
class Memory:
def load(self, position, data):
print(f"内存: 加载 {position} -> {data}")
class HardDrive:
def read(self, lba, size):
return f"硬盘数据: {lba}, {size}"
外观
class ComputerFacade:
def __init__(self):
self._cpu = CPU()
self._memory = Memory()
self._hard_drive = HardDrive()
def boot(self):
print("=== 启动电脑 ===")
self._cpu.freeze()
self._memory.load("0x00", self._hard_drive.read("100", "1024"))
self._cpu.jump("0x00")
self._cpu.execute()
print("=== 启动完成 ===")
使用
computer = ComputerFacade()
computer.boot()

2.2 简化复杂API

# 复杂的第三方API
class ComplexAPI:
def authenticate(self, username, password):
print(f"认证: {username}")
return "token123"
def get_user_profile(self, token):
print(f"获取用户: {token}")
return {"name": "Alice", "email": "alice@example.com"}
def update_user(self, token, data):
print(f"更新用户: {token}, {data}")
return True
def get_user_orders(self, token):
print(f"获取订单: {token}")
return [{"id": 1, "total": 99.99}]
def create_order(self, token, items):
print(f"创建订单: {token}, {items}")
return {"order_id": 123}
外观：简化API使用
class UserAPIFacade:
def __init__(self):
self._api = ComplexAPI()
self._token = None
def login(self, username, password):
self._token = self._api.authenticate(username, password)
return self._token
def get_profile(self):
if not self._token:
raise RuntimeError("未登录")
return self._api.get_user_profile(self._token)
def update_profile(self, data):
if not self._token:
raise RuntimeError("未登录")
return self._api.update_user(self._token, data)
def get_orders(self):
if not self._token:
raise RuntimeError("未登录")
return self._api.get_user_orders(self._token)
def create_order(self, items):
if not self._token:
raise RuntimeError("未登录")
return self._api.create_order(self._token, items)
使用
facade = UserAPIFacade()
facade.login("alice", "password")
profile = facade.get_profile()
orders = facade.get_orders()

三、实战案例

3.1 日志适配器

import logging
from datetime import datetime
统一的日志接口
class Logger:
def info(self, message):
pass
def error(self, message):
pass
def warning(self, message):
pass
FileLogger适配器
class FileLoggerAdapter(Logger):
def __init__(self, filename):
self._logger = logging.getLogger(filename)
self._logger.setLevel(logging.INFO)
if not self._logger.handlers:
handler = logging.FileHandler(filename)
formatter = logging.Formatter(
'%(asctime)s - %(levelname)s - %(message)s'
)
handler.setFormatter(formatter)
self._logger.addHandler(handler)
def info(self, message):
self._logger.info(message)
def error(self, message):
self._logger.error(message)
def warning(self, message):
self._logger.warning(message)
ConsoleLogger适配器
class ConsoleLoggerAdapter(Logger):
def __init__(self, name="app"):
self._logger = logging.getLogger(name)
self._logger.setLevel(logging.INFO)
if not self._logger.handlers:
handler = logging.StreamHandler()
formatter = logging.Formatter(
'[%(levelname)s] %(message)s'
)
handler.setFormatter(formatter)
self._logger.addHandler(handler)
def info(self, message):
self._logger.info(message)
def error(self, message):
self._logger.error(message)
def warning(self, message):
self._logger.warning(message)
使用
logger = FileLoggerAdapter('app.log')
logger.info("应用启动")
logger.error("发生错误")

3.2 通知系统外观

# 子系统
class EmailService:
def send(self, to, subject, body):
print(f"发送邮箱: {to}, {subject}")
class SMSService:
def send(self, phone, message):
print(f"发送短信: {phone}, {message}")
class PushService:
def send(self, user_id, title, message):
print(f"推送通知: {user_id}, {title}")
外观
class NotificationFacade:
def __init__(self):
self._email = EmailService()
self._sms = SMSService()
self._push = PushService()
def notify_user(self, user, message, channels=['email']):
"""统一通知接口"""
if 'email' in channels:
self._email.send(user['email'], '通知', message)
if 'sms' in channels:
self._sms.send(user['phone'], message)
if 'push' in channels:
self._push.send(user['id'], '新消息', message)
使用
user = {'id': 1, 'email': 'alice@example.com', 'phone': '13800138000'}
facade = NotificationFacade()
facade.notify_user(user, '您的订单已发货', channels=['email', 'push'])

3.3 第三方API集成

# 需要集成的第三方服务
class StripeAPI:
def create_customer(self, email):
return {'customer_id': 'cus_123'}
def create_charge(self, customer_id, amount):
return {'charge_id': 'ch_123'}
class PayPalAPI:
def create_account(self, email):
return {'account_id': 'pay_123'}
def execute_payment(self, account_id, amount):
return {'payment_id': 'pay_123'}
统一的支付接口
class PaymentGateway:
def create_customer(self, email):
pass
def charge(self, customer_id, amount):
pass
Stripe适配器
class StripeAdapter(PaymentGateway):
def __init__(self):
self._stripe = StripeAPI()
def create_customer(self, email):
result = self._stripe.create_customer(email)
return result['customer_id']
def charge(self, customer_id, amount):
result = self._stripe.create_charge(customer_id, amount)
return result['charge_id']
PayPal适配器
class PayPalAdapter(PaymentGateway):
def __init__(self):
self._paypal = PayPalAPI()
def create_customer(self, email):
result = self._paypal.create_account(email)
return result['account_id']
def charge(self, customer_id, amount):
result = self._paypal.execute_payment(customer_id, amount)
return result['payment_id']
使用
gateway = StripeAdapter()
customer_id = gateway.create_customer('alice@example.com')
charge_id = gateway.charge(customer_id, 100)

四、模式对比

4.1 适配器 vs 外观

# 适配器：转换接口
class Adaptee:
def specific_request(self):
pass
class Adapter:
def __init__(self, adaptee):
self._adaptee = adaptee
def request(self):
self._adaptee.specific_request()
外观：简化接口
class SubsystemA:
def method_a(self):
pass
class SubsystemB:
def method_b(self):
pass
class Facade:
def __init__(self):
self._a = SubsystemA()
self._b = SubsystemB()
def operation(self):
self._a.method_a()
self._b.method_b()