设计模式--装饰模式

  Decorator定义:
动态给一个对象添加一些额外的职责,就象在墙上刷油漆.使用Decorator模式相比用生成子类方式达到功能的扩充显得更为灵活.
  为什么使用Decorator?
我们通常可以使用继承来实现功能的拓展,如果这些需要拓展的功能的种类很繁多,那么势必生成很多子类,增加系统的复杂性,同时,使用继承实现功能拓展,我们必须可预见这些拓展功能,这些功能是编译时就确定了,是静态的.

  使用Decorator的理由是:这些功能需要由用户动态决定加入的方式和时机.Decorator提供了"即插即用"的方法,在运行期间决定何时增加何种功能.

package Decorator;

public abstract class SchoolReport {

	public abstract void report();
	
	public abstract void sign(String name);
	
}

package Decorator;

public abstract class Decorator extends SchoolReport {

	private SchoolReport report;

	public Decorator(SchoolReport report) {
		super();
		this.report = report;
	}
	
	public void report() {
		this.report.report();
	}
	
	public void sign(String name) {
		this.report.sign(name);
	}
}

package Decorator;

public class FouthGradeSchoolReport extends SchoolReport {

	@Override
	public void report() {
		System.out.println("ok");
	}

	@Override
	public void sign(String name) {
		System.out.println(name + "--");

	}

}

package Decorator;

public class HighSchoolDecorator extends Decorator {

	public HighSchoolDecorator(SchoolReport report) {
		super(report);
	}

	private void reportHighScore() {
		System.out.println("装饰后的");
	}

	@Override
	public void report() {
		this.reportHighScore();
		super.report();
	}


}

package Decorator;

public class SortDecorator extends Decorator {

	public SortDecorator(SchoolReport report) {
		super(report);
	}

	private void peportSort() {
		System.out.println("装饰排名");
	}

	@Override
	public void report() {
		super.report();
		this.peportSort();
	}

}

package Decorator;

public class Client {
	public static void main(String[] args) {
		SchoolReport report;
		report=new FouthGradeSchoolReport();
		report=new HighSchoolDecorator(report);
		report=new SortDecorator(report);
		report.report();
		report.sign("pass");
	}
}

评论

1 楼 peter635 2012-02-08  

好神奇的模式啊