应用场景

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将各个零件组装起来，比如我们需要组装手机，组装电脑等等。当构建的对象很复杂的时候，需要用到建造者模式。

本质

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将子组件的单独构造(由Builder来负责)和装配(由Director负责)进行了分离，这种模式适用于某个对象在构建过程复杂的情况下。由于将构建与装配解耦，不同的构建器，相同的装配也可以产生不同的对象。构建器相同,但装配不同，也可以产生不同的对象。

示例

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实体类

实体类表示各个部件具体的类，比如飞船应该有自己的实体类，然后飞船内部有轨道舱、逃逸塔、引擎的实体类。

package com.dy.xidian;public class AirShip {    private OrbitalModule orbitalModule;    private Engine engine;    private EscapeTower escapeTower;    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) {        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) {        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;    }}

构建器接口

为了解耦，我们需要为不同构建器定义自己的接口类。

package com.dy.xidian;public interface AirShipBuilder {    Engine builerEngine();    OrbitalModule builerOrbitalModule();    EscapeTower builderEscapeTower();}

 

构建器类

package com.dy.xidian;public class AirShipBuilderImpl implements AirShipBuilder {    @Override    public Engine builerEngine() {        System.out.println("发动机");        return new Engine("构建发动机");    }    @Override    public OrbitalModule builerOrbitalModule() {        System.out.println("轨道舱");        return new OrbitalModule("构建轨道舱");    }    @Override    public EscapeTower builderEscapeTower() {        System.out.println("逃逸塔");        return new EscapeTower("构建逃逸塔");    }}

 

装配器接口 

装配器通过装配应该返回一个装配好的对象

package com.dy.xidian;public interface AirShipDirector {    AirShip directorAirShip();}

 

装配器类

package com.dy.xidian;public class AirShipDirectorImpl implements AirShipDirector {    private AirShipBuilder builder;    public AirShipDirectorImpl(AirShipBuilder builder) {        this.builder = builder;    }    @Override    public AirShip directorAirShip() {        Engine e = builder.builerEngine();        OrbitalModule o = builder.builerOrbitalModule();        EscapeTower et = builder.builderEscapeTower();        AirShip ship = new AirShip();        ship.setEngine(e);        ship.setEscapeTower(et);        ship.setOrbitalModule(o);        return ship;    }}

 

装配器在装配时首先要通过builder类将各个部件构造出来,然后对其组装。这里的builder可以使用简单工厂模式来生成各个部件。

客户

package com.dy.xidian;public class Clinet {    public static void main(String[] args) {        AirShipDirector director = new AirShipDirectorImpl(                new AirShipBuilderImpl());        AirShip ship = director.directorAirShip();    }}

 

客户选择一个具体的构建器,让装配器对其进行组装。

应用

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StringBuilder类的append方法

JDOM中的DOMBuiler，SAXBuilder方法