原型模式详解-优快云博客

本文详细介绍了原型模式的概念及其在Java中的实现。通过一个具体的例子展示了如何使用原型模式来创建对象副本，以此达到提高性能的目的。文章涵盖了抽象类的定义、具体实体类的实现，以及缓存加载的过程。

原型模式（Prototype Pattern）是用于创建重复的对象，同时又能保证性能。这种类型的设计模式属于创建型模式，它提供了一种创建对象的最佳方式。

UML图
这里写图片描述

1.创建实现了Clonable的抽象类

public abstract class Shape implements Clonable{
    private String id;
    protected Stirng type;

    abstract void draw();

    public String getType(){
        return type;
    }

    public String getId(){
        return id;
    }

    public void setId(String id){
        this.id = id;
    }

    public Object clone(){
        Object clone = null;
        try{
            clone = super.clone();
        }catch(CloneNotSupportedException e){
            e.printStackTrace();
        }
        return clone;
    }
}

2.扩展了上面抽象类的实体类

public class Rectangle extends Shape{
    public Rectangle(){
        type = "Retangle";
    }

    @Override
    public void draw(){
        System.out.println("Inside Rectangle :draw() method.");
    }
}


public class Square extends Shape{
    public Square(){
        type="Squre";   
    }

    @Override
    public void draw(){
        System.out.println("Inside Square :draw() method");
    }
}


public class Circle extends Shape{
    public Circle(){
        type="Circle";
    }
    @Override
    public void draw(){
        System.out.println("Inside Circle :draw() method");
    }
}

3.创建一个类，从数据库中获取实体类，并把他们存储在一个Hashtable中

public class ShapeCache{
    private static Hashtable<String,Shape> shapeMap = new Hashtable<>(String,Shape);

    public static Shape getShape(String shapeId){
        Shape cachedShape = shapeMap.get(shapeId);
        return (Shape)cacheShape.clone();
    }

    public static void loadCache() {
      Circle circle = new Circle();
      circle.setId("1");
      shapeMap.put(circle.getId(),circle);

      Square square = new Square();
      square.setId("2");
      shapeMap.put(square.getId(),square);

      Rectangle rectangle = new Rectangle();
      rectangle.setId("3");
      shapeMap.put(rectangle.getId(),rectangle);
   }

}

4.运行

public class PrototypePatternDemo {
   public static void main(String[] args) {
      ShapeCache.loadCache();

      Shape clonedShape = (Shape) ShapeCache.getShape("1");
      System.out.println("Shape : " + clonedShape.getType());       

      Shape clonedShape2 = (Shape) ShapeCache.getShape("2");
      System.out.println("Shape : " + clonedShape2.getType());      

      Shape clonedShape3 = (Shape) ShapeCache.getShape("3");
      System.out.println("Shape : " + clonedShape3.getType());      
   }
}