本文目录导读：
我来为您展示一个完整的Java建造者模式案例，以订餐系统为例：
经典建造者模式案例
产品类（美食订单）
public class Meal {
private String mainDish; // 主菜
private String sideDish; // 配菜
private String drink; // 饮料
private String dessert; // 甜点
private boolean hasToy; // 是否包含玩具
private String notes; // 备注
// 私有构造函数，只能通过建造者创建
private Meal() {}
public void setMainDish(String mainDish) {
this.mainDish = mainDish;
}
// ... 其他setter方法
@Override
public String toString() {
return "Meal{" +
"mainDish='" + mainDish + '\'' +
", sideDish='" + sideDish + '\'' +
", drink='" + drink + '\'' +
", dessert='" + dessert + '\'' +
", hasToy=" + hasToy +
", notes='" + notes + '\'' +
'}';
}
}
抽象建造者接口
public interface MealBuilder {
MealBuilder buildMainDish(String dish);
MealBuilder buildSideDish(String side);
MealBuilder buildDrink(String drink);
MealBuilder buildDessert(String dessert);
MealBuilder buildToy(boolean hasToy);
MealBuilder buildNotes(String notes);
Meal build();
}
具体建造者实现
public class StandardMealBuilder implements MealBuilder {
private Meal meal;
public StandardMealBuilder() {
this.meal = new Meal();
}
@Override
public MealBuilder buildMainDish(String dish) {
meal.setMainDish(dish);
return this;
}
@Override
public MealBuilder buildSideDish(String side) {
meal.setSideDish(side);
return this;
}
@Override
public MealBuilder buildDrink(String drink) {
meal.setDrink(drink);
return this;
}
@Override
public MealBuilder buildDessert(String dessert) {
meal.setDessert(dessert);
return this;
}
@Override
public MealBuilder buildToy(boolean hasToy) {
meal.setHasToy(hasToy);
return this;
}
@Override
public MealBuilder buildNotes(String notes) {
meal.setNotes(notes);
return this;
}
@Override
public Meal build() {
return meal;
}
}
导演类（可选，用于控制构建顺序）
public class MealDirector {
private MealBuilder builder;
public MealDirector(MealBuilder builder) {
this.builder = builder;
}
// 儿童套餐
public Meal constructKidsMeal() {
return builder
.buildMainDish("迷你汉堡")
.buildSideDish("薯条")
.buildDrink("橙汁")
.buildDessert("冰淇淋")
.buildToy(true)
.buildNotes("不要洋葱")
.build();
}
// 健康套餐
public Meal constructHealthyMeal() {
return builder
.buildMainDish("鸡胸肉沙拉")
.buildSideDish("蔬菜")
.buildDrink("绿茶")
.buildNotes("少盐")
.build();
}
}
客户端代码
public class BuilderPatternDemo {
public static void main(String[] args) {
System.out.println("=== 建造者模式示例 ===\n");
// 方式1：直接使用建造者
Meal meal = new StandardMealBuilder()
.buildMainDish("牛肉汉堡")
.buildSideDish("薯条")
.buildDrink("可乐")
.buildDessert("苹果派")
.buildToy(true)
.buildNotes("多放番茄酱")
.build();
System.out.println("自定义订单: " + meal);
// 方式2：使用导演类
MealBuilder builder = new StandardMealBuilder();
MealDirector director = new MealDirector(builder);
Meal kidsMeal = director.constructKidsMeal();
System.out.println("\n儿童套餐: " + kidsMeal);
Meal healthyMeal = director.constructHealthyMeal();
System.out.println("\n健康套餐: " + healthyMeal);
}
}
简化版（使用Lombok或静态工厂）
// Lombok @Builder 方式
import lombok.Builder;
import lombok.ToString;
@Builder
@ToString
public class Product {
private String name;
private String brand;
private double price;
private String category;
private String manufacturer;
private int stock;
}
链条式建造者（更灵活）
public class Computer {
// 必需属性
private final String cpu;
private final String ram;
// 可选属性
private String gpu;
private String storage;
private String display;
private String keyboard;
private String mouse;
private Computer(Builder builder) {
this.cpu = builder.cpu;
this.ram = builder.ram;
this.gpu = builder.gpu;
this.storage = builder.storage;
this.display = builder.display;
this.keyboard = builder.keyboard;
this.mouse = builder.mouse;
}
public static class Builder {
// 必需参数
private final String cpu;
private final String ram;
// 可选参数
private String gpu;
private String storage;
private String display;
private String keyboard;
private String mouse;
public Builder(String cpu, String ram) { // 必需参数在构造函数中
this.cpu = cpu;
this.ram = ram;
}
public Builder gpu(String val) { gpu = val; return this; }
public Builder storage(String val) { storage = val; return this; }
public Builder display(String val) { display = val; return this; }
public Builder keyboard(String val) { keyboard = val; return this; }
public Builder mouse(String val) { mouse = val; return this; }
public Computer build() {
return new Computer(this);
}
}
@Override
public String toString() {
return "Computer{" +
"cpu='" + cpu + '\'' +
", ram='" + ram + '\'' +
", gpu='" + gpu + '\'' +
", storage='" + storage + '\'' +
", display='" + display + '\'' +
", keyboard='" + keyboard + '\'' +
", mouse='" + mouse + '\'' +
'}';
}
public static void main(String[] args) {
Computer computer = new Computer.Builder("i9-13900K", "32GB DDR5")
.gpu("RTX 4090")
.storage("2TB NVMe SSD")
.display("27\" 4K")
.keyboard("机械键盘")
.build();
System.out.println(computer);
}
}
建造者模式优点总结
✔ 优点：
- 将复杂对象的构建过程分离
- 灵活性强，可以按需构建
- 代码可读性好，参数语义清晰
- 支持链式调用
❌ 缺点：
- 对于简单对象可能过度设计
- 需要额外创建Builder类
使用场景
- 参数过多的对象：超过4-5个参数
- 参数有可选性：不是所有参数都需要
- 参数之间有依赖关系：构建顺序重要
- 不可变对象：需要防止修改
这种模式在java.lang.StringBuilder、java.util.stream.Stream等JDK类中都有应用。
