GOF23设计模式之建造者模式

GOF23设计模式之建造者模式

场景：

我们要建造一个复杂的产品。比如：神州飞船，Iphone。这个复杂的产品的创建。有这样的一个问题需要处理：

装配这些子组件是不是有个步骤问题？

实际开发中，我们所需要的对象构建时，也非常复杂，有很多步骤需要处理时。

本质：

1）分离了对象子组件的单独构造（由 Builder 来负责）和装配（由 Director 负责）。从而可以构造出复杂的对象。这个模式适用于：某个对象的构建过程复杂的情况下使用。

2）由于时下按了构建和装配的解耦。不同的构建起，相同的装配，也可以做出不同的对象；相同的构建起，不同的装配顺序也可以做出不同的对象。也就算实现了构建算法、装配算法的解耦，实现了更好的复用。

package cn.taosir.design.create.builders;
/**
 * 宇宙飞船
 * @author taosir
 *
 */
public class AirShip {
    private OrbitalModule orbitalModule;//轨道舱
    private Engine engine;//发动机
    private EscapeTower escapeTower;//逃逸塔
    public OrbitalModule getOrbitalModule() {return orbitalModule;}
    public void setOrbitalModule(OrbitalModule orbitalModule) {this.orbitalModule = orbitalModule;}
    public Engine getEngine() {return engine;}
    public void setEngine(Engine engine) {this.engine = engine;}
    public EscapeTower getEscapeTower() {return escapeTower;}
    public void setEscapeTower(EscapeTower escapeTower) {this.escapeTower = escapeTower;}
}

class OrbitalModule{
    private String name;
    public OrbitalModule(String name) {super();this.name = name;}
    public String getName() {return name;}
    public void setName(String name) {this.name = name;}
}
class Engine{
    private String name;
    public Engine(String name) {super();this.name = name;}
    public String getName() {return name;}
    public void setName(String name) {this.name = name;}
}
class EscapeTower{
    private String name;
    public EscapeTower(String name) {super();this.name = name;}
    public String getName() {return name;}
    public void setName(String name) {this.name = name;}
}

package cn.taosir.design.create.builders;

public interface AirShipBuilder {
    Engine builderEngine();
    OrbitalModule builderOrbitalModule();
    EscapeTower builderEscapeTower();
}

package cn.taosir.design.create.builders;

public interface AirShipDirector {
    /**
     * 组装飞船对象
     * @return
     */
    AirShip directAirShip();
}

package cn.taosir.design.create.builders;

public class TaoSirAirShipBuilder implements AirShipBuilder{
    @Override
    public Engine builderEngine() {
        System.out.println("构建发动机...");
        return new Engine("发动机");
    }
    @Override
    public OrbitalModule builderOrbitalModule() {
        System.out.println("构建轨道舱...");
        return new OrbitalModule("轨道舱");
    }

    @Override
    public EscapeTower builderEscapeTower() {
        System.out.println("构建逃逸塔...");
        return new EscapeTower("逃逸塔");
    }

}

package cn.taosir.design.create.builders;

public class TaoSirAirShipDirector implements AirShipDirector{

    private AirShipBuilder builder;

    public TaoSirAirShipDirector(AirShipBuilder builder) {
        this.builder=builder;
    }
    
    @Override
    public AirShip directAirShip() {
        Engine e=builder.builderEngine();
        OrbitalModule o=builder.builderOrbitalModule();
        EscapeTower et=builder.builderEscapeTower();
        //装配飞船对象
        AirShip ship=new AirShip();
        ship.setEngine(e);
        ship.setEscapeTower(et);
        ship.setOrbitalModule(o);
        return ship;
    }

}

package cn.taosir.design.create.builders;

public class Client {
    public static void main(String[] args) {
        AirShipDirector director=new TaoSirAirShipDirector(new TaoSirAirShipBuilder());
        AirShip ship = director.directAirShip();
        System.out.println(ship.getEngine());
    }
}

开发中的应用场景

StringBuilder类的append方法

SQL中的PreparedStatement

JDOM中，DomBuilder、SAXBuilder