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装饰模式(Decotator):动态地给一个对象添加一些额外的职责,就增加功能来说,装饰模式比生成子类更加灵活
这是在网上找的关于装饰模式的类图,
http://img0.imgtn.bdimg.com/it/u=3834882730,1020120806&fm=214&gp=0.jpg
Component是定义一个对象的接口,可以给这些对象动态地添加职责,ConcreteComponet是定义了一个具体的对象,也可以给这个对象添加一些职责。Decorator装饰抽象类,继承了Component从外类扩展Componet的功能。至于ConcreteDecorator就是具体的装饰对象
public abstract class Component {
public abstract void operation();
}
public class ConcreteComponent extends Component {
@Override
public void operation() {
System.out.println("具体对象的操作");
}
}
public abstract class Decorator extends Component{
protected Component component;
public void setComponent(Component component) {
this.component = component;
}
@Override
public void operation() {
if (component!=null)
{
component.operation();
}
}
}
public class ConcreteDecoratorA extends Decorator{
private String addedState;
@Override
public void operation() {
super.operation();
addedState="new State";
System.out.println("具体装饰对象A的操作");
}
}
public class ConcreteDecoratorB extends Decorator {
@Override
public void operation() {
super.operation();
addBehavior();
}
private void addBehavior()
{
System.out.println("具体装饰对象B的操作");
}
}
public class Main {
public static void main(String[] args) {
ConcreteComponent c=new ConcreteComponent();
ConcreteDecoratorA d1=new ConcreteDecoratorA();
ConcreteDecoratorB d2=new ConcreteDecoratorB();
//用装饰类A去装饰c
d1.setComponent(c);
//用装饰类A去装饰C
d2.setComponent(d1);
d2.operation();
}
}
下面再举一个具体应用到装饰对象的例子:
一个人要穿衣服,搭配服饰。下面是具体的实现:
public class Person {
private String name;
public Person() {
}
public Person(String name) {
this.name = name;
}
public void show()
{
System.out.println("装扮的"+name);
}
}
public abstract class Finery extends Person{
public Person person;
public void setPerson(Person person) {
this.person = person;
}
@Override
public void show() {
if(null!=person)
{
person.show();
}
}
}
public class BigTrouser extends Finery {
@Override
public void show() {
System.out.print("大垮裤"+" ");
super.show();
}
}
public class Dress extends Finery {
@Override
public void show() {
System.out.print("裙子"+" ");
super.show();
}
}
public class Shoes extends Finery{
@Override
public void show() {
System.out.print("破球鞋"+" ");
super.show();
}
}
public class TShirts extends Finery {
@Override
public void show() {
System.out.print("大T恤"+" ");
super.show();
}
}
public class Main {
public static void main(String[] args) {
Person p=new Person("小明") ;
System.out.println("第一种打扮");
TShirts tShirts=new TShirts();
Dress dress=new Dress();
Shoes shoes=new Shoes();
tShirts.setPerson(p);
dress.setPerson(tShirts);
shoes.setPerson(dress);
shoes.show();
System.out.println("第二种打扮");
Shoes shoes1=new Shoes();
BigTrouser bigTrouser=new BigTrouser();
shoes1.setPerson(p);
bigTrouser.setPerson(shoes1);
bigTrouser.show();
}
}
装饰模式的优点就是把类中的装饰功能从类中搬移去除,这样可以简化原有的类
有效地把类的核心职责和装饰功能区分开了,而且可以去除相关类中的重复值逻辑