【设计模式】建造者设计模式

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建造者设计模式

定义：将对象的创建和属性赋值分离，建造的过程不需要知道，只需要通过构建者去操作。

仍以小汽车为例：

public class Car{
	private String basePlate;
	private String door;
	private Sting frame;

	//... setter & getter constractor
}

public abstract class Builder {
	public abstract void buildBasePlate(String basePlate);
	public abstract void buildDoor(String door);
	public abstract void buildFrame(String frame);

	public abstract Car makeCar();
}

public class CarBuilder extends Builder{
	
	Car car = new Car();
	
	@Override
	public void buildBasePlate(String basePlate){
		car.setBasePlate(basePlate);
	}

	@Override
	public void buildDoor(String door){
		car.setBasePlate(door);
	}

	@Override
	public void buildFrame(String frame){
		car.setBasePlate(frame);
	}

	@Override
	public Car makeCar(){
		return car;
	}
}

public class Engineer{
	private CarBuilder carBuilder;

	public void setCarBuilder(CarBuilder carBuilder) {
		this.carBuilder = carBuilder;
	}

	public Car makeCar(String basePlate, String door, String frame) {
		carBuilder.buildBasePlate(basePlate);
		carBuilder.buildDoor(door);
		carBuilder.buildFrame(frame);

		return carBuilder.makeCar();
	}
}

总结：作者个人理解建造者设计模式的核心就是通过构建抽象建造者Builder + 实例建造者CarBuilder掩饰对象的构建过程与赋值过程，设计一个实例构建者Engineer来完成对象的构造。