浅谈GOF设计模式之建造者模式（五）

建造者模式的本质
代码实现
使用场景

建造者模式的本质

一般与工厂模式搭配使用
1.分离了对象子组件的单独构造（有bulider来负责）和装配（由Director负责）。从而可以构造出复杂的对象：某个对象构建相对复杂的情况下使用。
2.由于实现了构建和装配的解耦。不同的的解耦器，相同的装配，也可以做出不同的对象；
相同的构造器，不同的装配顺序也可以做出不同的对象。也就实现了
构建算法、装配算法的解耦，实现了更好的复用。

代码实现

代码逻辑分块

1.产品类-(组件类)
2.建造者(创建一个产品对象的各个部件的抽象接口) 具体建造者（实现建造者接口，构建和装配各个部件）
3.指挥者类(构建一个使用建造者接口的对象，调用创建类，创建组件，按照不同的顺序组装成不同的产品)

传统实现方式

产品类

package com.bjsxt.builder.ji;



/**
 * @Author JJL
 * @Date 2020/9/11 14:48
 * @Version 1.0
 */
//飞船类 -- 产品类
public class JiShip {

	private OrbitalModule orbitalModule;  //轨道舱
	private Engine engine; //发动机
	private EscapeTower escapeTower;  //逃逸塔
	
	
	public void launch(){
		System.out.println("老子要发射！");
	}

	
	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;
	}
	
	
	
}

//轨道舱
class OrbitalModule{
	private String name;

	public OrbitalModule(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	
}

//发动机
class Engine {
	private String name;

	public Engine(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	
	
}

//逃逸仓
class EscapeTower{
	private String name;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public EscapeTower(String name) {
		super();
		this.name = name;
	}
	
}

建造者

package com.bjsxt.builder.ji;

import com.bjsxt.builder.ji.Engine;
import com.bjsxt.builder.ji.EscapeTower;
import com.bjsxt.builder.ji.OrbitalModule;

/**
 * @Author JJL
 * @Date 2020/9/11 14:48
 * @Version 1.0
 */
public interface IJiShipBuilder {
    /**
     * BuildPart
     * @return
     */
    Engine builderEngine();
    OrbitalModule builderOrbitalModule();
    EscapeTower builderEscapeTower();

    /**
     * getResult
     * @return
     */
    JiShip buildShip();
}



package com.bjsxt.builder.ji;

/**
 * @Author JJL
 * @Date 2020/9/11 15:14
 * @Version 1.0
 */
public class ConJiShipBudiler implements IJiShipBuilder{

    private JiShip jiShip = null;
    private Engine engine = null;
    private EscapeTower escapeTower = null;
    private OrbitalModule orbitalModule = null;

    /**
     * 构造器 -- 这里进行取值
     */
    public ConJiShipBudiler() {
        if(jiShip == null){
            jiShip = new JiShip();
        }
    }

    /**
     * buildPart
     * @return
     */
    @Override
    public Engine builderEngine() {
        engine = new Engine("老子的发动机");
        return engine;
    }

    /**
     * buildPart
     * @return
     */
    @Override
    public OrbitalModule builderOrbitalModule() {
        orbitalModule = new OrbitalModule("老子的轨道舱");
        return orbitalModule;
    }

    /**
     * buildPart
     * @return
     */
    @Override
    public EscapeTower builderEscapeTower() {
        escapeTower = new EscapeTower("老子的逃逸塔");
        return escapeTower;
    }


    /**
     * getResult -- 建造者 -- 组装过程
     * @return
     */
    @Override
    public JiShip buildShip() {
        jiShip.setEngine(engine);
        jiShip.setEscapeTower(escapeTower);
        jiShip.setOrbitalModule(orbitalModule);
        return jiShip;
    }
}

指挥者

package com.bjsxt.builder.ji;

/**
 * @Author JJL
 * @Date 2020/9/11 16:01
 * @Version 1.0
 */
public class Director {

    /**
     * 用来指挥建造过程
     */
    public JiShip Construct(IJiShipBuilder builder) {
        builder.builderEngine();
        builder.builderEscapeTower();
        builder.builderOrbitalModule();
        return builder.buildShip();
    }
}

调用者

package com.bjsxt.builder.ji;

/**
 * @Author JJL
 * @Date 2020/9/11 19:39
 * @Version 1.0
 */
public class Cilent {
    public static void main(String[] args) {
        Director director = new Director();
        JiShip jiShip = director.Construct(new ConJiShipBudiler());
        System.out.println(jiShip.getEngine().getName() + "" + jiShip.getEscapeTower().getName() + jiShip.getOrbitalModule().getName());
        jiShip.launch();
    }
}

GOF实现方式

产品以及产品组件


//飞船类
public class AirShip {
	
	private OrbitalModule orbitalModule;  //轨道舱
	private Engine engine; //发动机
	private EscapeTower escapeTower;  //逃逸塔
	
	
	public void launch(){
		System.out.println("发射！");
	}
	
	
	
	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;
	}
	
	
	
}

//轨道舱
class OrbitalModule{
	private String name;

	public OrbitalModule(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	
}

//发动机
class Engine {
	private String name;

	public Engine(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	
	
}

//逃逸仓
class EscapeTower{
	private String name;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public EscapeTower(String name) {
		super();
		this.name = name;
	}
	
}

建造者具体建造者块

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

//构建者--创建具体的产品组件
public class SxtAirShipBuilder implements AirShipBuilder {
	//StringBuilder, 以后学习XML解析中，JDOM库中的类：DomBuilder,SaxBuilder

	/**
	 * 创建方法的返回实例可以跟单例模式和工厂模式结合起来
	 * @return
	 */
	@Override
	public Engine builderEngine() {
		System.out.println("构建尚学堂牌发动机！");
		return new Engine("尚学堂牌发动机！");
	}

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

	@Override
	public OrbitalModule builderOrbitalModule() {
		System.out.println("构建轨道舱");
		return new OrbitalModule("尚学堂牌轨道舱");
	}	
	
}

指挥者块

//装配者（装配组件返回产品）
public interface AirShipDirector {
	
	/**
	 * 组装飞船对象
	 * @return
	 */
	AirShip   directAirShip();
	
}

/**
 * 装配者，将构建者传进来之后，按照顺序等（装配过程）装配成具体的产品  -- 组装
 */
public class SxtAirshipDirector implements AirShipDirector {

	private AirShipBuilder builder;

	public SxtAirshipDirector(AirShipBuilder builder) {
		this.builder = builder;
	}


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

}

调用块

public class Client {
	public static void main(String[] args) {
		
		AirShipDirector director = new SxtAirshipDirector(new SxtAirShipBuilder());

		AirShip ship = director.directAirShip();
		
		System.out.println(ship.getEngine().getName());
		
		ship.launch();
		
	}
}

变种

具体建造者

public class ExtendByJiShipBuilder implements AirShipBuilder{

    @Override
    public Engine builderEngine() {
        System.out.println("构建发动机X2");
        return new Engine("X2");
    }

    @Override
    public OrbitalModule builderOrbitalModule() {
        System.out.println("构建轨道舱X2");
        return new OrbitalModule("X2");
    }

    @Override
    public EscapeTower builderEscapeTower() {
        System.out.println("构建逃逸塔X2");
        return new EscapeTower("X2");
    }
}

指挥者类

public class ExtendByJiShipDirector implements AirShipDirector{

    private AirShipBuilder builder;


    public void setBuilder(AirShipBuilder b){
        this.builder = b;
    }

    @Override
    public AirShip directAirShip() {
        AirShip ship = new AirShip();
        ship.setEngine(builder.builderEngine());
        ship.setEscapeTower(builder.builderEscapeTower());
        ship.setOrbitalModule(builder.builderOrbitalModule());

        return ship;
    }
}

调用者

public class Client {
	public static void main(String[] args) {
		
		AirShipDirector director = new SxtAirshipDirector(new SxtAirShipBuilder());

		AirShip ship = director.directAirShip();
		
		System.out.println(ship.getEngine().getName());
		
		ship.launch();


		//变种
		ExtendByJiShipDirector extendByJiShipDirector = new ExtendByJiShipDirector();

		ExtendByJiShipBuilder builder = new ExtendByJiShipBuilder();

		extendByJiShipDirector.setBuilder(builder);

		AirShip eShip = extendByJiShipDirector.directAirShip();
		System.out.println(eShip.getEngine().getName());
		eShip.launch();

	}
}

使用场景

1.StringBuilder类的append方法
StringBuilder继承了AbstractStringBuilder，而AbstractStringBuilder实现了appendable
StringBuilder：指挥者类，持有具体建造者的引用，由于StringBuilder继承了AbstractStringBuilder，这里StringBuilder通过super来作为具体建造者的引用。

AbstractStringBuilder：具体建造者，它实现了appendable接口的append(Character c)方法。

appendable：抽象建造者，定义了创建对象的接口。

  public StringBuilder(CharSequence seq) {
        this(seq.length() + 16);
        append(seq);
    }

    @Override
    public StringBuilder append(Object obj) {
        return append(String.valueOf(obj));
    }

    @Override
    public StringBuilder append(String str) {
        super.append(str);
        return this;
    }

2.SQL中的PreparedStatement

3.JDOM中，DomBuilder、SAXBuilder
SAXBuilder

SAXBuilder builder=new SAXBuilder(false); 
Reader returnQuote = new StringReader(rexml);
Document doc = builder.build(returnQuote);
得到根元素：
Element books=doc.getRootElement();
在JDOM中所有的节点（DOM中的概念）都是一个org.jdom.Element 类，当然他的子节点也是一个org.jdom.Element类。
得到元素（节点）的集合：
List booklist=books.getChildren(“book”);

DomBuilder

DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Documentdoc=builder.newDocument();
Element root=doc.createElement("root");
Text text=doc.createText("Thisistheroot");
root.appendChild(text);
doc.appendChild(root);




DOMBuilder builder=new DOMBuilder();
Document doc=builder.build(newFile("jdom_test.xml"));
SAXBuilder builder=new SAXBuilder();
Document doc=builder.build(url);