写在后面

记录学习设计模式的笔记
进步对设计模式的灵活运用

学习地址

https://www.bilibili.com/video/BV1G4411c7N4

https://www.bilibili.com/video/BV1Np4y1z7BU

参考文章

http://c.biancheng.net/view/1317.html

我的项目源码
https://gitee.com/zhuang-kang/DesignPattern

10，适配器模式

10.1 适配器模式的定义和特点

适配器模式（Adapter）的定义如下：将一个类的接口转换成客户心愿的另外一个接口，使得本来因为接口不兼容而不能一起工作的那些类能一起工作。适配器模式分为类结构型模式和对象结构型模式两种，前者类之间的耦合度比后者高。

该模式的次要长处如下：

客户端通过适配器能够通明地调用指标接口。
复用了现存的类，程序员不须要批改原有代码而重用现有的适配者类。
将指标类和适配者类解耦，解决了指标类和适配者类接口不统一的问题。
在很多业务场景中合乎开闭准则。

其毛病是：

适配器编写过程须要联合业务场景全面思考，可能会减少零碎的复杂性。
减少代码浏览难度，升高代码可读性，过多应用适配器会使零碎代码变得凌乱。

10.2 适配器模式的构造与实现

10.2.1 适配器模式的构造

指标（Target）接口：以后零碎业务所期待的接口，它能够是抽象类或接口。
适配者（Adaptee）类：它是被拜访和适配的现存组件库中的组件接口。
适配器（Adapter）类：它是一个转换器，通过继承或援用适配者的对象，把适配者接口转换成指标接口，让客户按指标接口的格局拜访适配者。

10.2.2 代码实现

10.2.2.1 类适配器模式

Voltage5V 指标接口

package com.zhuang.adapter.classadapter;/** * @Classname Voltage5V * @Description  定义直流电 * @Date 2021/3/21 14:14 * @Created by dell */public interface Voltage5V {    //定义一个规范充电器来实现    public int output5V();}

Voltage220V

package com.zhuang.adapter.classadapter;/** * @Classname Voltage220V * @Description 创立交流电 * @Date 2021/3/21 14:13 * @Created by dell */public class Voltage220V {    public int output220V() {        System.out.println("voltage 输入220伏");        return 220;    }}

VoltageAdapter

package com.zhuang.adapter.classadapter;/** * @Classname VoltageAdapter * @Description 创立充电器 * @Date 2021/3/21 14:14 * @Created by dell */public class VoltageAdapter extends Voltage220V implements Voltage5V {    @Override    public int output5V() {        //获取交流电220V        int output220V = output220V();        //转为5V        int output5V = output220V / 44;        System.out.println("VoltageAdapter 输入5伏");        return output5V;    }}

Phone

package com.zhuang.adapter.classadapter;/** * @Classname Phone * @Description 手机类 * @Date 2021/3/21 14:15 * @Created by dell */public class Phone {    public void charging(Voltage5V voltage5V) {        if (voltage5V.output5V() == 5) {            System.out.println("电压5伏，能够充电");        } else if (voltage5V.output5V() > 5) {            System.out.println("电压过大，不能够充电");        }    }}

Client

package com.zhuang.adapter.classadapter;/** * @Classname Client * @Description  客户端类 * @Date 2021/3/21 14:15 * @Created by dell */public class Client {    public static void main(String[] args) {        System.out.println("==类适配器==");        Phone phone = new Phone();        phone.charging(new VoltageAdapter());    }}

类适配器模式注意事项和细节

Java是单继承机制，所以类适配器须要继承适配者（Adaptee，指Voltage220V）类，这点算是一个毛病，除此之外还必须要求指标（Target，指Voltage5V）必须是接口，有肯定局限性；
适配者Voltage220V类的办法在适配器VoltageAdapter类中都会裸露进去，也减少了应用的老本。然而因为其继承了适配者Voltage220V类，所以它能够依据需要重写该类的办法，使得适配器VoltageAdapter类的灵活性加强了。

10.2.2.2 对象适配器模式

Voltage5V

package com.zhuang.adapter.objectadapter;/** * @Classname Voltage5V * @Description 充电5V * @Date 2021/3/21 14:32 * @Created by dell */public interface Voltage5V {    //定义一个规范充电器来实现    public int output5V();}

Voltage220V

package com.zhuang.adapter.objectadapter;/** * @Classname Voltage220V * @Description 输入220V类 * @Date 2021/3/21 14:32 * @Created by dell */public class Voltage220V {    public int output220V() {        System.out.println("voltage 输入220伏");        return 220;    }}

VoltageAdapter

package com.zhuang.adapter.objectadapter;/** * @Classname VoltageAdapter * @Description 适配器类 * @Date 2021/3/21 14:33 * @Created by dell */public class VoltageAdapter implements Voltage5V {    private Voltage220V voltage220V;    public VoltageAdapter(Voltage220V voltage220V) {        this.voltage220V = voltage220V;    }    @Override    public int output5V() {        //获取交流电220V        int output220V = voltage220V.output220V();        //转为5V        int output5V = output220V / 44;        System.out.println("VoltageAdapter 输入5伏");        return output5V;    }}

Phone

package com.zhuang.adapter.objectadapter;/** * @Classname Phone * @Description 手机类 * @Date 2021/3/21 14:33 * @Created by dell */public class Phone {    public void charging(Voltage5V voltage5V) {        if (voltage5V.output5V() == 5) {            System.out.println("电压5伏，能够充电");        } else if (voltage5V.output5V() > 5) {            System.out.println("电压过大，不能够充电");        }    }}

Client

package com.zhuang.adapter.objectadapter;/** * @Classname Client * @Description 对象适配器测试类 * @Date 2021/3/21 14:33 * @Created by dell */public class Client {    public static void main(String[] args) {        System.out.println("==对象适配器==");        Phone phone = new Phone();        phone.charging(new VoltageAdapter(new Voltage220V()));    }}

对象适配器模式注意事项和细节

对象适配器和类适配器其实算是同一种思维，只不过实现形式不同。
依据合成复用准则，应用组合代替继承，所以它解决了类适配器中VoltageAdapter必须继承Voltage220V的局限性问题，也不再强制要求Voltage5V必须是接口。应用老本更低，更灵便。因而，对象适配器模式是适配器模式罕用的一种。

10.2.2.3 接口适配器模式

Animation

package com.zhuang.adapter.interfaceadapter;/** * @Classname Animation * @Description 动画接口 * @Date 2021/3/21 14:47 * @Created by dell */public interface Animation {    public void method1();    public void method2();    public void method3();    public void method4();    public void method5();}

AnimationAdapter

package com.zhuang.adapter.interfaceadapter;/** * @Classname AnimationAdapter * @Description  接口适配器类 * @Date 2021/3/21 14:48 * @Created by dell */public class AnimationAdapter implements Animation {    //全副都空实现    @Override    public void method1() {    }    @Override    public void method2() {    }    @Override    public void method3() {    }    @Override    public void method4() {    }    @Override    public void method5() {    }}

JFrameAnimation

package com.zhuang.adapter.interfaceadapter;/** * @Classname JFrameAnimation * @Description 适配器子类 * @Date 2021/3/21 14:49 * @Created by dell */public class JFrameAnimation extends AnimationAdapter {    @Override    public void method1() {        System.out.println("method1()被调用了...");    }    @Override    public void method2() {        System.out.println("method2()被调用了...");    }}

Client

package com.zhuang.adapter.interfaceadapter;/** * @Classname Client * @Description  客户端类 * @Date 2021/3/21 14:50 * @Created by dell */public class Client {    public static void main(String[] args) {        JFrameAnimation animation = new JFrameAnimation();        animation.method1();        animation.method2();    }}

10.3 SpringMVC源码解析

Controller

package com.zhuang.adapter.springmvc;/** * @Classname Controller * @Description  springmvc的Controller源码 * @Date 2021/3/21 14:53 * @Created by dell *///多种Controller实现public interface Controller {}class HttpController implements Controller {    public void doHttpHandler() {        System.out.println("http...");    }}class SimpleController implements Controller {    public void doSimplerHandler() {        System.out.println("simple...");    }}class AnnotationController implements Controller {    public void doAnnotationHandler() {        System.out.println("annotation...");    }}

DispatchServlet

package com.zhuang.adapter.springmvc;import java.util.ArrayList;import java.util.List;/** * @Classname DispatchServlet * @Description  springmvc的DispatchServlet源码 * @Date 2021/3/21 14:52 * @Created by dell */public class DispatchServlet {    public static List<HandlerAdapter> handlerAdapters = new ArrayList<HandlerAdapter>();    public DispatchServlet() {        handlerAdapters.add(new AnnotationHandlerAdapter());        handlerAdapters.add(new HttpHandlerAdapter());        handlerAdapters.add(new SimpleHandlerAdapter());    }    public void doDispatch() {        // 此处模仿SpringMVC从request取handler的对象，        // 适配器能够获取到心愿的Controller        HttpController controller = new HttpController();        // AnnotationController controller = new AnnotationController();        //SimpleController controller = new SimpleController();        // 失去对应适配器        HandlerAdapter adapter = getHandler(controller);        // 通过适配器执行对应的controller对应办法        adapter.handle(controller);    }    public HandlerAdapter getHandler(Controller controller) {        //遍历：依据失去的controller(handler), 返回对应适配器        for (HandlerAdapter adapter : this.handlerAdapters) {            if (adapter.supports(controller)) {                return adapter;            }        }        return null;    }    public static void main(String[] args) {        new DispatchServlet().doDispatch(); // http...    }}

HandlerAdapter

package com.zhuang.adapter.springmvc;/** * @Classname HandlerAdapter * @Description  springmvc的HandlerAdapter源码 * @Date 2021/3/21 14:53 * @Created by dell *////定义一个Adapter接口public interface HandlerAdapter {    public boolean supports(Object handler);    public void handle(Object handler);}// 多种适配器类class SimpleHandlerAdapter implements HandlerAdapter {    @Override    public void handle(Object handler) {        ((SimpleController) handler).doSimplerHandler();    }    @Override    public boolean supports(Object handler) {        return (handler instanceof SimpleController);    }}class HttpHandlerAdapter implements HandlerAdapter {    @Override    public void handle(Object handler) {        ((HttpController) handler).doHttpHandler();    }    @Override    public boolean supports(Object handler) {        return (handler instanceof HttpController);    }}class AnnotationHandlerAdapter implements HandlerAdapter {    @Override    public void handle(Object handler) {        ((AnnotationController) handler).doAnnotationHandler();    }    @Override    public boolean supports(Object handler) {        return (handler instanceof AnnotationController);    }}

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