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。
建造者模式的本质
- 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，不同的装备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。
示例
package 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;
}
}
package builder;
public interface AirShipBuilder {
Engine builderEngine();
OrbitalModule builderOrbitalModule();
EscapeTower builderEscapeTower();
}
package builder;
public interface AirShipDirector {
/**
* 组装飞船对象
* @return
*/
AirShip directAirShip();
}
package builder;
public class MyAirShipBuilder implements AirShipBuilder{
//StringBuilder,DomBuilder,SaxBuilder
public Engine builderEngine() {
System.out.println("构建发动机");
return new Engine("发动机");
}
public OrbitalModule builderOrbitalModule() {
System.out.println("构建轨道舱");
return new OrbitalModule("轨道舱");
}
public EscapeTower builderEscapeTower() {
System.out.println("构建逃逸塔");
return new EscapeTower("逃逸塔");
}
}
package builder;
public class MyAirShipDirector implements AirShipDirector{
private AirShipBuilder builder;
public MyAirShipDirector(AirShipBuilder builder) {
this.builder = builder;
}
public AirShip directAirShip() {
Engine engine = builder.builderEngine();
OrbitalModule orbitalModule = builder.builderOrbitalModule();
EscapeTower escapeTower = builder.builderEscapeTower();
//装配
AirShip airShip = new AirShip();
airShip.setEngine(engine);
airShip.setOrbitalModule(orbitalModule);
airShip.setEscapeTower(escapeTower);
return airShip;
}
}
package builder;
public class Client {
public static void main(String[] args) {
AirShipDirector director = new MyAirShipDirector(new MyAirShipBuilder());
AirShip airShip = director.directAirShip();
System.out.println(airShip.getEngine().getName());
airShip.launch();
}
}
开发中应用场景:
- StringBuilder类的append方法
- SQL中的PreparedStatement
- JDOM中,DomBuilder、SAXBuilder
