设计模式-7-装饰器模式

装饰器模式：允许向一个现有的对象添加新的功能，同时又不改变其结构。他作为一个现有的类的封装。



1.定义一个接口作为原始类

package com.structuralPattern.decorator.edition1;

public interface Primitive {
void operation();
}


2.Source类继承Primitive并实现operation方法
package com.structuralPattern.decorator.edition1;

public class Source implements Primitive{
@Override
public void operation() {
System.out.println("原始类的方法");
}

}


3.定义装饰器类（明显Decorator中使用了“对象适配器模式”，通过定义变量primitive类承接Source的实例，利用构造函数进行初始化）
package com.structuralPattern.decorator.edition1;

public class Decorator implements Primitive {
public Primitive primitive;
public Decorator(Primitive primitive) {
this.primitive = primitive;
}

@Override
public void operation() {

}

}


4.定义实际装饰器
package com.structuralPattern.decorator.edition1;

public class Decorator1 extends Decorator{
public Decorator1(Primitive primitive) {
super(primitive);
}

@Override
public void operation() {
System.out.println("第一个装饰器前--添加的新功能");
primitive.operation();
System.out.println("第一个装饰器后--添加的新功能");
}
}

package com.structuralPattern.decorator.edition1;

public class Decorator2 extends Decorator{
public Decorator2(Primitive primitive) {
super(primitive);
}

@Override
public void operation() {
System.out.println("第二个装饰器前--添加的新功能");
primitive.operation();
System.out.println("第二个装饰器后--添加的新功能");
}
}

package com.structuralPattern.decorator.edition1;

public class DecoratorTest {
public static void main(String[] args) {
Primitive primitive = new Source();

//装饰类对象
Primitive pd1 = new Decorator1(primitive);
pd1.operation();

//装饰类对象
Primitive pd2 = new Decorator1(primitive);
pd2.operation();

System.out.println("============");

Primitive pd = new Decorator1(new Decorator2(primitive));
pd.operation();
}
}