设计模式之装饰器模式

装饰器模式：根据一个基本的对象，可以动态的对他进行改造，扩展功能，这里强调的是自定义扩展，注意和工厂模式进行区分
核心在于，实现Compent的那个基本对象的构造方法，由于继承，实现的关系都间接实现了Compent接口，然后通过装饰器对构造器中传入的对象进行扩展，需要什么功能调取什么装饰器就可以。通过这种模式可以实现自定义的扩展对象功能

类图：

AdminDecorator

package decorator;

public class AdminDecorator extends NavbarDecorator{
    public AdminDecorator(Navbar decoratedNavbar) {
        super(decoratedNavbar);
    }

    @Override
    public void base() {
        super.base();
        //扩展功能
        addBar();
    }

    private void addBar() {
        System.out.println("+ 管理员栏位！");
    }
}

BaseNavbar:

package decorator;

public class BaseNavbar implements Navbar {

    @Override
    public void base() {
        System.out.println("导航栏   基本栏位！");
    }
}

GuestDecorator:

package decorator;

public class GuestDecorator extends NavbarDecorator{
    public GuestDecorator(Navbar decoratedNavbar) {
        super(decoratedNavbar);
    }

    @Override
    public void base() {
        super.base();
        //扩展功能
        addBar();
    }

    private void addBar() {
        System.out.println(" + 游客栏位！");
    }
}

Navbar:

package decorator;

public class GuestDecorator extends NavbarDecorator{
    public GuestDecorator(Navbar decoratedNavbar) {
        super(decoratedNavbar);
    }

    @Override
    public void base() {
        super.base();
        //扩展功能
        addBar();
    }

    private void addBar() {
        System.out.println(" + 游客栏位！");
    }
}

NavbarDecorator:

package decorator;

public abstract class NavbarDecorator implements Navbar {

    protected Navbar decoratedNavbar;

    public NavbarDecorator(Navbar decoratedNavbar){
        super();
        this.decoratedNavbar = decoratedNavbar;
    }

    @Override
    public void base() {
        decoratedNavbar.base();
    }
}

test:

package decorator;

public class test {

    public static void main(String[] args) {
        Navbar bar = new BaseNavbar();
        System.out.println("========无装饰=========");
        bar.base();

        Navbar adminDecorator = new AdminDecorator(bar);
        System.out.println("========管理员装饰=========");
        adminDecorator.base();

        System.out.println("=========经过管理员装饰 + 游客装饰=========");
        Navbar guestNabar = new GuestDecorator(adminDecorator);
        guestNabar.base();
    }
}

运行结果：