Java设计模式泛型化之装饰模式

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装饰模式是Java开发中常见的设计模式之一。我们在Service层的设计实现中就用到了装饰模式。

对于它的理解是这样的：

在原有已经实现的功能上添加新的功能实现。

其结构是这样的：

一个原有的抽象层（接口或者抽象类）对应既有抽象层的实现层一个Decorator类来实现原有抽象层一个或多个具体的Decorator类扩展这个Decorator实现一个调用者

来看看代码：

原有的抽象层

public interface Origin {public void doSomething();public void doOtherthing();}

既有抽象层的实现层

public class OriginImpl implements Origin {@Overridepublic void doSomething() {System.out.println("Origin do something.");}@Overridepublic void doOtherthing() {System.out.println("Origin do other thing.");}}

Decorator类

public abstract class Decorator implements Origin {private Origin org;public Decorator(Origin org) {this.org = org;}@Overridepublic void doSomething() {org.doSomething();}@Overridepublic void doOtherthing() {org.doOtherthing();}}

不同的装饰者

public class DecoratorA extends Decorator {public DecoratorA(Origin org) {super(org);}private void doNothing() {System.out.println("Decorator A do nothing.");}private void doAnotherthing() {System.out.println("Decorator A do another thing.");}@Overridepublic void doSomething() {doNothing();super.doSomething();}@Overridepublic void doOtherthing() {super.doOtherthing();doAnotherthing();}}

public class DecoratorB extends Decorator {public DecoratorB(Origin org) {super(org);}private void before() {System.out.println("Decorator B do it before.");}private void after() {System.out.println("Decorator B do it after.");}@Overridepublic void doSomething() {super.doSomething();after();}@Overridepublic void doOtherthing() {before();super.doOtherthing();}}

调用者

public class DecoratorCaller {public static void main(String[] args) {Origin org = new OriginImpl();DecoratorA decA = new DecoratorA(org);DecoratorB decB = new DecoratorB(org);decA.doSomething();decB.doOtherthing();}}

那么，如何泛型化呢？

不难看出，Decorator才是关键所在。因此，泛型化处理是这样的：

Decorator

@SuppressWarnings("all")public abstract class Decorator<T extends Origin> implements Origin {private T t;public Decorator(T t) {    this.t = t;}@Overridepublic void doSomething() {t.doSomething();}@Overridepublic void doOtherthing() {t.doOtherthing();}}

具体实现类

public class DecoratorA<T extends Origin> extends Decorator<T> {public DecoratorA(T t) {super(t);}private void doNothing() {System.out.println("Decorator A do nothing.");}private void doAnotherthing() {System.out.println("Decorator A do another thing.");}@Overridepublic void doSomething() {doNothing();super.doSomething();}@Overridepublic void doOtherthing() {super.doOtherthing();doAnotherthing();}}

public class DecoratorB<T extends Origin> extends Decorator<T> {public DecoratorB(T t) {super(t);}private void before() {System.out.println("Decorator B do it before.");}private void after() {System.out.println("Decorator B do it after.");}@Overridepublic void doSomething() {super.doSomething();after();}@Overridepublic void doOtherthing() {before();super.doOtherthing();}}

调用者

public class DecoratorCaller {public static void main(String[] args) {Origin org = new OriginImpl();DecoratorA<Origin> decA = new DecoratorA<Origin>(org);DecoratorB<Origin> decB = new DecoratorB<Origin>(org);decA.doSomething();decB.doOtherthing();}}

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