创建者模式Builder

创建者模式：

分离对象子组件的单独构造(由Builder来负责)和装配(由Director负责)，对象的构造比较复杂时使用 该模式。

类图：

Builder 抽象建造者接口，规范各个组成部分的构建。

　　ConcreteBuilder 具体建造者角色，实现组成部分的构建，并提供示例。

　　Product 产品角色，创建返回的对象。

　　Director 导演者角色，负责创建以及使用。

优点：

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成不同的对象，相同的构建器，不同的装配顺序也可以生产成不同的对象。也就是实现了构造算法和装配算法的解耦，实现了更好的复用。

应用场景：

StringBuilder类的append方法。

SQL中的PreparedStatement

JDOM中，DomBuilder SAXBuilder

创建者模式Demo

 package builder.domain;

 /**
  * 宇宙飞船
  *
  */
 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;
     }
 }

 package builder.domain;

 public 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;
     }
 }

 package builder.domain;

 public 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;
     }
 }

 package builder.domain;

 public 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;
     }

 }

 package builder.service;

 import builder.domain.Engine;
 import builder.domain.EscapeTower;
 import builder.domain.OrbitalModule;

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

 package builder.service;

 import builder.domain.Engine;
 import builder.domain.EscapeTower;
 import builder.domain.OrbitalModule;

 public class AirShipBuilderImpl implements IAirShipBuilder {
     //StringBuilder, 以后学习XML解析中，JDOM库中的类：DomBuilder,SaxBuilder
     @Override
     public Engine builderEngine() {
         // TODO Auto-generated method stub
         System.out.println("构建发动机！");
         return new Engine("发动机！");
     }

     @Override
     public OrbitalModule builderOrbitalModule() {
         // TODO Auto-generated method stub
         System.out.println("构建轨道舱");
         return new OrbitalModule("轨道舱");
     }

     @Override
     public EscapeTower builderEscapeTower() {
         // TODO Auto-generated method stub
         System.out.println("构建逃逸塔");
         return new EscapeTower("逃逸塔");
     }

 }

 package builder;

 import builder.domain.AirShip;

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

 package builder;

 import builder.domain.AirShip;
 import builder.domain.Engine;
 import builder.domain.EscapeTower;
 import builder.domain.OrbitalModule;
 import builder.service.IAirShipBuilder;

 public class AirshipDirectorImpl implements IAirShipDirector {
     private IAirShipBuilder builder;

     public AirshipDirectorImpl(IAirShipBuilder builder) {
         this.builder = builder;
     }

     @Override
     public AirShip directAirShip() {
         // TODO Auto-generated method stub
         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;
     }

 }

 package builder;

 import builder.domain.AirShip;
 import builder.service.AirShipBuilderImpl;

 public class Client {

     public static void main(String[] args) {
         // TODO Auto-generated method stub
         IAirShipDirector director = new AirshipDirectorImpl(new AirShipBuilderImpl());

         AirShip ship = director.directAirShip();

         System.out.println(ship.getEngine().getName());

         ship.launch();
     }

 }