创建型模式 - 建造者模式 (Builder Pattern)

建造者模式是一种创建型设计模式，它将一个复杂对象的构建与表示分离，使得同样的构建过程可以创建不同的表示。

需求描述
在游戏开发中，创建一个复杂的游戏角色，角色具有多种属性，如姓名、性别、职业、武器等。不同类型的角色这些属性的组合和设置方式可能不同。使用建造者模式可以将角色的创建过程和具体表示分离，方便创建不同类型的角色。

java">// 产品类：游戏角色
class GameCharacter {private String name;private String gender;private String profession;private String weapon;public void setName(String name) {this.name = name;}public void setGender(String gender) {this.gender = gender;}public void setProfession(String profession) {this.profession = profession;}public void setWeapon(String weapon) {this.weapon = weapon;}@Overridepublic String toString() {return "GameCharacter{" +"name='" + name + '\'' +", gender='" + gender + '\'' +", profession='" + profession + '\'' +", weapon='" + weapon + '\'' +'}';}
}// 抽象建造者类
abstract class CharacterBuilder {protected GameCharacter character;public GameCharacter getCharacter() {return character;}public void createNewCharacter() {character = new GameCharacter();}public abstract void buildName();public abstract void buildGender();public abstract void buildProfession();public abstract void buildWeapon();
}// 具体建造者类：战士角色建造者
class WarriorBuilder extends CharacterBuilder {@Overridepublic void buildName() {character.setName("战士-亚瑟");}@Overridepublic void buildGender() {character.setGender("男");}@Overridepublic void buildProfession() {character.setProfession("战士");}@Overridepublic void buildWeapon() {character.setWeapon("大剑");}
}// 具体建造者类：法师角色建造者
class MageBuilder extends CharacterBuilder {@Overridepublic void buildName() {character.setName("法师-梅林");}@Overridepublic void buildGender() {character.setGender("男");}@Overridepublic void buildProfession() {character.setProfession("法师");}@Overridepublic void buildWeapon() {character.setWeapon("法杖");}
}// 指挥者类
class CharacterDirector {private CharacterBuilder builder;public CharacterDirector(CharacterBuilder builder) {this.builder = builder;}public GameCharacter constructCharacter() {builder.createNewCharacter();builder.buildName();builder.buildGender();builder.buildProfession();builder.buildWeapon();return builder.getCharacter();}
}// 客户端代码
public class GameCharacterBuilderExample {public static void main(String[] args) {// 创建战士角色CharacterBuilder warriorBuilder = new WarriorBuilder();CharacterDirector warriorDirector = new CharacterDirector(warriorBuilder);GameCharacter warrior = warriorDirector.constructCharacter();System.out.println(warrior);// 创建法师角色CharacterBuilder mageBuilder = new MageBuilder();CharacterDirector mageDirector = new CharacterDirector(mageBuilder);GameCharacter mage = mageDirector.constructCharacter();System.out.println(mage);}
}

建造者模式拓展

使用这一种方式，就相当于代码中调用方法者来充当指挥者角色。

java">public class Phone {private String cpu;private String screen;private String memory;private String brand;// 私有构造函数private Phone(Builder builder) {this.cpu = builder.cpu;this.screen = builder.screen;this.memory = builder.memory;	this.brand = builder.brand;}// 内部类构造器public static final class Builder {private String cpu;private String screen;private String memory;private String brand;public Builder cpu(String cpu) {this.cpu = cpu;return this;}public Builder screen(String screen) {this.screen = screen;return this;}public Builder memory(String memory) {this.memory = memory;return this;}public Builder brand(String brand) {this.brand = brand;return this;}// 利用 Java 内部类可以访问外部类的私有成员变量的特性,调用私有构造方法返回 Phone 对象public Phone build() {return new Phone(this);}}
}// 使用的时候非常方便也非常清晰
Phone iPhone20 = new Phone.Builder().cpu("Apple A100").screen("LG屏幕").memory("三星内存").brand("Apple").build();// btw: 这种使用方式还是挺常见的, 在一些第三方库配置 Config 的时候,例如 Rocket MQ 配置