设计模式（三）建造者模式

建造模式的本质：

——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。

——由于实现了构建和装配的解耦。不同的构建器，相同的装配，也可以做出不同的对象；相同的构建器，不同的装配顺序也可以做出不同的对象。也就是实现了构建算法、装配算法的解耦，实现了更好的复用。

例：

1. 定义飞船类以及发动机、轨道舱、逃逸塔类：

package com.ztq.builder;

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;
    }
    
}

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){
        this.name = name;
    }
    public String getName() {
        return name;
    }

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

2. 定义AirShipBuilder接口：

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

3. 定义AirShipDirector接口：

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

4. 定义实现AirShipBuilder接口的类：

public class ZtqAirShipBuilder implements AirShipBuilder{

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

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

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

5. 定义实现AirShipDirector接口的类：

public class ZtqAirShipDirector implements AirShipDirector{
    
    private AirShipBuilder builder;
    
    public ZtqAirShipDirector(AirShipBuilder builder) {
        this.builder = builder;
    }
    
    @Override
    public AirShip directAirShip(){
        Engine e = builder.builderEngine();
        OrbitalModule o = builder.builderOrbitalModule();
        EscapeTower es = builder.builderEscapeTower();
        
        AirShip ship = new AirShip();
        ship.setEngine(e);
        ship.setOrbitalModule(o);
        ship.setEscapeTower(es);
        
        return ship;
    }
}

6. 定义测试类：

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

打印结果：

构建ztq牌发动机！
构建ztq牌轨道舱！
构建ztq牌逃逸塔！
ztq牌发动机
发射！

UML图：