04.建造者模式的终极手册：从快餐定制到航天飞船的组装哲学

序章：当你的对象比巨无霸汉堡更复杂时

🍔 订餐困境：
你想点一份包含三层牛肉、双份芝士、不要酸黄瓜、加辣蛋黄酱、搭配番薯条的定制汉堡——普通构造器需要8个参数且充满null值！建造者模式就是你的"订单配置系统"，让你用优雅的方式组装复杂对象。

---

一、基础建造师入门课

1.1 传统Builder模式实现

// 宇宙飞船的零件清单
public class SpaceShip {private final String engine;      // 必选private final int fuel;           // 必选private String weaponSystem;      // 可选private boolean escapePod;         // 可选private String aiCore;            // 可选private SpaceShip(Builder builder) {this.engine = builder.engine;this.fuel = builder.fuel;this.weaponSystem = builder.weaponSystem;this.escapePod = builder.escapePod;this.aiCore = builder.aiCore;}// 建造者控制台public static class Builder {private final String engine;private final int fuel;private String weaponSystem = "None";private boolean escapePod;private String aiCore = "Basic";public Builder(String engine, int fuel) {this.engine = engine;this.fuel = fuel;}public Builder weaponSystem(String system) {this.weaponSystem = system;return this;}public Builder escapePod(boolean hasPod) {this.escapePod = hasPod;return this;}public Builder aiCore(String core) {this.aiCore = core;return this;}public SpaceShip build() {validate();return new SpaceShip(this);}private void validate() {if (fuel < 1000) {throw new IllegalArgumentException("燃料不足最低阈值！");}}}
}// 使用示例：组装歼星舰
SpaceShip deathStar = new SpaceShip.Builder("超物质引擎", 5000).weaponSystem("超级激光炮").escapePod(true).aiCore("天网").build();

模式优势：

• 强制必选参数校验
• 可选参数灵活组合
• 构建过程线程安全
• 参数顺序无关性

---

二、现代建造师进化指南

2.1 流式接口（Fluent API）

// 咖啡订单构建器
public class Coffee {private String size;private boolean milk;private int sugar;private String extra;public static class Builder {private Coffee coffee = new Coffee();public Builder size(String size) {coffee.size = size;return this;}public Builder milk(boolean milk) {coffee.milk = milk;return this;}public Builder sugar(int cubes) {coffee.sugar = cubes;return this;}public Builder extra(String item) {coffee.extra = item;return this;}public Coffee brew() {if (coffee.size == null) {throw new IllegalStateException("必须选择杯型！");}return coffee;}}
}// 使用链式调用
Coffee myCoffee = new Coffee.Builder().size("大杯").milk(true).sugar(2).extra("焦糖").brew();

2.2 Lombok建造者（极简主义）

@Builder
@ToString
public class SmartPhone {@NonNullprivate String model;@Builder.Defaultprivate int ram = 8;     // 默认值@Builder.Defaultprivate int storage = 128;private boolean nfc;private String color;
}// 自动生成建造者
SmartPhone phone = SmartPhone.builder().model("XPhone 15").ram(12).color("星际黑").build();

---

三、高级建造工厂

3.1 泛型建造者

// 通用建造者接口
public interface Builder<T> {T build();
}// 房屋建造实现
public class HouseBuilder implements Builder<House> {private House house = new House();public HouseBuilder addRooms(int rooms) {house.setRooms(rooms);return this;}public HouseBuilder addPool() {house.setHasPool(true);return this;}@Overridepublic House build() {return house;}
}// 导演类控制建造流程
public class Architect {public House buildMansion(Builder<House> builder) {return ((HouseBuilder) builder).addRooms(10).addPool().build();}
}

3.2 线程安全建造者

public class ThreadSafePCBuilder {private volatile String cpu;private volatile String gpu;private volatile int ram;public synchronized ThreadSafePCBuilder setCpu(String cpu) {this.cpu = cpu;return this;}public synchronized ThreadSafePCBuilder setGpu(String gpu) {this.gpu = gpu;return this;}public synchronized ThreadSafePCBuilder setRam(int ram) {this.ram = ram;return this;}public PC build() {return new PC(cpu, gpu, ram);}
}

---

四、特殊建造技巧

4.1 组合建造者

// 组合汽车部件
public class CarBuilder {private EngineBuilder engineBuilder = new EngineBuilder();private WheelBuilder wheelBuilder = new WheelBuilder();public CarBuilder withV8Engine() {engineBuilder.setType("V8");return this;}public CarBuilder withSportWheels() {wheelBuilder.setType("Sport");return this;}public Car build() {return new Car(engineBuilder.build(), wheelBuilder.build());}
}// 创建跑车
Car sportsCar = new CarBuilder().withV8Engine().withSportWheels().build();

4.2 分阶段建造

// 分阶段接口
public interface Stage1 {Stage2 setCPU(String cpu);
}public interface Stage2 {Stage3 setGPU(String gpu);
}public interface Stage3 {PCBuilder setRAM(int ram);
}public class PCBuilder implements Stage1, Stage2, Stage3 {// 强制按顺序配置@Overridepublic Stage2 setCPU(String cpu) { /*...*/ }@Overridepublic Stage3 setGPU(String gpu) { /*...*/ }@Overridepublic PC build() { /*...*/ }
}// 确保正确配置顺序
PC gamingPC = new PCBuilder().setCPU("i9").setGPU("RTX 4090").setRAM(64).build();

---

五、Spring中的建造者模式

5.1 结合工厂模式

@Configuration
public class Config {@Bean@Scope("prototype")public PizzaBuilder pizzaBuilder() {return new PizzaBuilder();}
}@Service
public class PizzaService {private final PizzaBuilder builder;public PizzaService(PizzaBuilder builder) {this.builder = builder;}public Pizza createSpecialPizza() {return builder.size("XL").crust("芝士卷边").topping("双份芝士").build();}
}

5.2 配置类建造者

@ConfigurationProperties(prefix = "mail")
public class MailConfig {private String host;private int port;// Builder生成配置对象public static MailConfigBuilder builder() {return new MailConfigBuilder();}
}// application.yml配置
mail:host: smtp.example.comport: 587

---

建造者模式选择指南

实现方式	适用场景	优点	缺点
传统Builder	需要严格校验的复杂对象	线程安全，强校验	代码量大
流式接口	可选参数多的配置类	调用直观，易扩展	无法强制必选参数
Lombok Builder	快速开发简单DTO	代码极简	灵活性受限
泛型建造者	需要统一构建接口的系统	提高代码复用率	类型转换需要处理
分阶段建造	必须按步骤配置的对象	保证配置顺序	使用复杂度稍高

---

终章：建造者的宇宙法则

当你面对以下场景时，请召唤建造者模式：

1. 对象包含多个可选参数（超过4个参数）
2. 需要不同组合的构造方式
3. 要求对象不可变（Immutable）
4. 需要分步构造复杂对象

禁忌时刻：

• 当对象非常简单（3个以下参数）时
• 当构造过程不需要灵活性时
• 当性能要求极高（纳秒级）的场景

最后，记住一位资深架构师的名言：“建造者模式不是为了炫技，而是为了在复杂性与可维护性之间找到完美平衡。”

创作挑战：
如果要实现一个支持撤销操作的建造者（比如用户可以回退到上一步配置），如何设计这样的建造者结构？把你的设计草图留在评论区吧！🚀👩💻