UML class diagram In the above
UML class diagram, the client class that requires a target interface cannot reuse the adaptee class directly because its interface doesn't conform to the target interface. Instead, the client works through an adapter class that implements the target interface in terms of adaptee: • The object adapter way implements the target interface by delegating to an adaptee object at run-time (adaptee.specificOperation()). • The class adapter way implements the target interface by inheriting from an adaptee class at compile-time (specificOperation()).
Object adapter pattern In this adapter pattern, the adapter contains an instance of the class it wraps. In this situation, the adapter makes calls to the instance of the wrapped
object.
Class adapter pattern This adapter pattern uses multiple
polymorphic interfaces implementing or inheriting both the interface that is expected and the interface that is pre-existing. It is typical for the expected interface to be created as a pure
interface class, especially in
languages such as
Java (before JDK 1.8) that do not support
multiple inheritance of classes.
A further form of runtime adapter pattern Motivation from compile time solution It is desired for to supply with some data, let us suppose some data. A compile time solution is: classB.setStringData(classA.getStringData()); However, suppose that the format of the string data must be varied. A compile time solution is to use inheritance: public class Format1ClassA extends ClassA { @Override public String getStringData() { return format(toString()); } } and perhaps create the correctly "formatting" object at runtime by means of the
factory pattern.
Run-time adapter solution A solution using "adapters" proceeds as follows: {{ordered list|list-style-type=lower-roman interface StringProvider { public String getStringData(); } public class ClassAFormat1 implements StringProvider { private ClassA classA = null; public ClassAFormat1(final ClassA a) { classA = a; } public String getStringData() { return format(classA.getStringData()); } private String format(final String sourceValue) { // Manipulate the source string into a format required // by the object needing the source object's data return sourceValue.trim(); } } public class ClassAFormat1Adapter extends Adapter { public Object adapt(final Object anObject) { return new ClassAFormat1((ClassA) anObject); } } AdapterFactory.getInstance().registerAdapter(ClassA.class, ClassAFormat1Adapter.class, "format1"); Adapter adapter = AdapterFactory.getInstance() .getAdapterFromTo(ClassA.class, StringProvider.class, "format1"); StringProvider provider = (StringProvider) adapter.adapt(classA); String string = provider.getStringData(); classB.setStringData(string); or more concisely: classB.setStringData(((StringProvider)AdapterFactory.getInstance() .getAdapterFromTo(ClassA.class, StringProvider.class, "format1") .adapt(classA)) .getStringData() ); Adapter adapter = AdapterFactory.getInstance() .getAdapterFromTo(ClassA.class, StringProvider.class, "format2"); Adapter adapter = AdapterFactory.getInstance() .getAdapterFromTo(ClassA.class, ImageProvider.class, "format2"); ImageProvider provider = (ImageProvider) adapter.adapt(classA); classC.setImage(provider.getImage()); }}
Implementation of the adapter pattern When implementing the adapter pattern, for clarity, one can apply the class name to the provider implementation; for example, . It should have a constructor method with an adaptee class variable as a parameter. This parameter will be passed to an instance member of . When the clientMethod is called, it will have access to the adaptee instance that allows for accessing the required data of the adaptee and performing operations on that data that generates the desired output.
Java package org.wikipedia.examples; interface ILightningPhone { void recharge(); void useLightning(); } interface IMicroUsbPhone { void recharge(); void useMicroUsb(); } class Iphone implements ILightningPhone { private boolean connector; @Override public void useLightning() { connector = true; System.out.println("Lightning connected"); } @Override public void recharge() { if (connector) { System.out.println("Recharge started"); System.out.println("Recharge finished"); } else { System.out.println("Connect Lightning first"); } } } class Android implements IMicroUsbPhone { private boolean connector; @Override public void useMicroUsb() { connector = true; System.out.println("MicroUsb connected"); } @Override public void recharge() { if (connector) { System.out.println("Recharge started"); System.out.println("Recharge finished"); } else { System.out.println("Connect MicroUsb first"); } } } /* exposing the target interface while wrapping source object */ class LightningToMicroUsbAdapter implements IMicroUsbPhone { private final ILightningPhone lightningPhone; public LightningToMicroUsbAdapter(ILightningPhone lightningPhone) { this.lightningPhone = lightningPhone; } @Override public void useMicroUsb() { System.out.println("MicroUsb connected"); lightningPhone.useLightning(); } @Override public void recharge() { lightningPhone.recharge(); } } public class AdapterDemo { static void rechargeMicroUsbPhone(IMicroUsbPhone phone) { phone.useMicroUsb(); phone.recharge(); } static void rechargeLightningPhone(ILightningPhone phone) { phone.useLightning(); phone.recharge(); } public static void main(String[] args) { Android android = new Android(); Iphone iPhone = new Iphone(); System.out.println("Recharging android with MicroUsb"); rechargeMicroUsbPhone(android); System.out.println("Recharging iPhone with Lightning"); rechargeLightningPhone(iPhone); System.out.println("Recharging iPhone with MicroUsb"); rechargeMicroUsbPhone(new LightningToMicroUsbAdapter(iPhone)); } } Output Recharging android with MicroUsb MicroUsb connected Recharge started Recharge finished Recharging iPhone with Lightning Lightning connected Recharge started Recharge finished Recharging iPhone with MicroUsb MicroUsb connected Lightning connected Recharge started Recharge finished
Python """ Adapter pattern example. """ from abc import ABCMeta, abstractmethod from typing import NoReturn RECHARGE: list[str] = ["Recharge started.", "Recharge finished."] POWER_ADAPTERS: dict[str, str] = {"Android": "MicroUSB", "iPhone": "Lightning"} CONNECTED_MSG: str = "{} connected." CONNECT_FIRST_MSG: str = "Connect {} first." class RechargeTemplate(metaclass = ABCMeta): @abstractmethod def recharge(self) -> NoReturn: raise NotImplementedError("You should implement this.") class FormatIPhone(RechargeTemplate): @abstractmethod def use_lightning(self) -> NoReturn: raise NotImplementedError("You should implement this.") class FormatAndroid(RechargeTemplate): @abstractmethod def use_micro_usb(self) -> NoReturn: raise NotImplementedError("You should implement this.") class IPhone(FormatIPhone): __name__: str = "iPhone" def __init__(self): self.connector: bool = False def use_lightning(self) -> None: self.connector = True print(CONNECTED_MSG.format(POWER_ADAPTERS[self.__name__])) def recharge(self) -> None: if self.connector: for state in RECHARGE: print(state) else: print(CONNECT_FIRST_MSG.format(POWER_ADAPTERS[self.__name__])) class Android(FormatAndroid): __name__: str = "Android" def __init__(self) -> None: self.connector: bool = False def use_micro_usb(self) -> None: self.connector = True print(CONNECTED_MSG.format(POWER_ADAPTERS[self.__name__])) def recharge(self) -> None: if self.connector: for state in RECHARGE: print(state) else: print(CONNECT_FIRST_MSG.format(POWER_ADAPTERS[self.__name__])) class IPhoneAdapter(FormatAndroid): def __init__(self, mobile: FormatAndroid) -> None: self.mobile: FormatAndroid = mobile def recharge(self) -> None: self.mobile.recharge() def use_micro_usb(self) -> None: print(CONNECTED_MSG.format(POWER_ADAPTERS["Android"])) self.mobile.use_lightning() class AndroidRecharger: def __init__(self) -> None: self.phone: Android = Android() self.phone.use_micro_usb() self.phone.recharge() class IPhoneMicroUSBRecharger: def __init__(self) -> None: self.phone: IPhone = IPhone() self.phone_adapter: IPhoneAdapter = IPhoneAdapter(self.phone) self.phone_adapter.use_micro_usb() self.phone_adapter.recharge() class IPhoneRecharger: def __init__(self) -> None: self.phone: IPhone = IPhone() self.phone.use_lightning() self.phone.recharge() print("Recharging Android with MicroUSB recharger.") AndroidRecharger() print() print("Recharging iPhone with MicroUSB using adapter pattern.") IPhoneMicroUSBRecharger() print() print("Recharging iPhone with iPhone recharger.") IPhoneRecharger()
C# namespace Wikipedia.Examples; using System; interface ILightningPhone { void ConnectLightning(); void Recharge(); } interface IUsbPhone { void ConnectUsb(); void Recharge(); } sealed class AndroidPhone : IUsbPhone { private bool isConnected; public void ConnectUsb() { this.isConnected = true; Console.WriteLine("Android phone connected."); } public void Recharge() { if (this.isConnected) { Console.WriteLine("Android phone recharging."); } else { Console.WriteLine("Connect the USB cable first."); } } } sealed class ApplePhone : ILightningPhone { private bool isConnected; public void ConnectLightning() { this.isConnected = true; Console.WriteLine("Apple phone connected."); } public void Recharge() { if (this.isConnected) { Console.WriteLine("Apple phone recharging."); } else { Console.WriteLine("Connect the Lightning cable first."); } } } sealed class LightningToUsbAdapter : IUsbPhone { private readonly ILightningPhone lightningPhone; private bool isConnected; public LightningToUsbAdapter(ILightningPhone lightningPhone) { this.lightningPhone = lightningPhone; } public void ConnectUsb() { this.lightningPhone.ConnectLightning(); } public void Recharge() { this.lightningPhone.Recharge(); } } public class AdapterDemo { static void Main(string[] args) { ILightningPhone applePhone = new ApplePhone(); IUsbPhone adapterCable = new LightningToUsbAdapter(applePhone); adapterCable.ConnectUsb(); adapterCable.Recharge(); } } Output: Apple phone connected. Apple phone recharging. ==See also==