程序员经常会遇到灵魂拷问:你有对象吗?
没有,但我可以 new 一个!
public class GirlFriend{ private String name; private int age; // 省略 getter & setter ... public static void main(String[] args){ GirlFriend myGirlFriend = new GirlFriend(); myGirlFriend.setName("小美"); myGirlFriend.setAge(18); } }
没问题,老铁!但如果对象的属性太多,咋办?
public class GirlFriend{ private String name; private int age; private int bust; private int waist; private int hips; private List<String> hobby; private String birthday; private String address; private String mobile; private String email; private String hairColor; private Map<String, String> gift; // 等等等等 ... // 省略 getter & setter ... public static void main(String[] args){ GirlFriend myGirlFriend = new GirlFriend(); myGirlFriend.setName("小美"); myGirlFriend.setAge(18); myGirlFriend.setBust(33); myGirlFriend.setWaist(23); myGirlFriend.setHips(33); myGirlFriend.setBirthday("2001-10-26"); myGirlFriend.setAddress("上海浦东"); myGirlFriend.setMobile("18688888888"); myGirlFriend.setEmail("pretty-xiaomei@qq.com"); myGirlFriend.setHairColor("浅棕色带点微卷"); List<String> hobby = new ArrayList<>(); hobby.add("逛街"); hobby.add("购物"); hobby.add("买东西"); myGirlFriend.setHobby(hobby); Map<String, String> gift = new HashMap<>(); gift.put("情人节礼物", "LBR 1912女王时代"); gift.put("生日礼物", "迪奥烈焰蓝金"); gift.put("纪念日礼物", "阿玛尼红管唇釉"); myGirlFriend.setGift(gift); // 等等等等 ... } }
GirlFriend{name='小美' , age=18 , bust=33 , waist=23 , hips=33 , hobby=[逛街, 购物, 买东西] , birthday='2001-10-26' , address='上海浦东' , mobile='18688888888' , email='pretty-xiaomei@qq.com' , hairColor='浅棕色带点微卷' , gift={情人节礼物=LBR 1912女王时代, 生日礼物=迪奥烈焰蓝金, 纪念日礼物=阿玛尼红管唇釉} }
GirlFriend 是很美,但写起来也太麻烦了吧。
说说缺点:实例化和设置属性分开,不好维护;变量名重复写。
莫慌,看法宝~
这里不再介绍其他 Builder 实现方式,直接祭出最实用的 通用Builder :
适用于所有类,不需要改造原来类,不需要 lombok 插件支持。
先看看使用姿势:
public class GirlFriend{ // 省略属性 ... // 省略 getter & setter ... // 为了演示方便,加几个聚合方法 public void addHobby(String hobby){ this.hobby = Optional.ofNullable(this.hobby).orElse(new ArrayList<>()); this.hobby.add(hobby); } public void addGift(String day, String gift){ this.gift = Optional.ofNullable(this.gift).orElse(new HashMap<>()); this.gift.put(day, gift); } public void setVitalStatistics(int bust, int waist, int hips){ this.bust = bust; this.waist = waist; this.hips = hips; } public static void main(String[] args){ GirlFriend myGirlFriend = Builder.of(GirlFriend::new) .with(GirlFriend::setName, "小美") .with(GirlFriend::setAge, 18) .with(GirlFriend::setVitalStatistics, 33, 23, 33) .with(GirlFriend::setBirthday, "2001-10-26") .with(GirlFriend::setAddress, "上海浦东") .with(GirlFriend::setMobile, "18688888888") .with(GirlFriend::setEmail, "pretty-xiaomei@qq.com") .with(GirlFriend::setHairColor, "浅棕色带点微卷") .with(GirlFriend::addHobby, "逛街") .with(GirlFriend::addHobby, "购物") .with(GirlFriend::addHobby, "买东西") .with(GirlFriend::addGift, "情人节礼物", "LBR 1912女王时代") .with(GirlFriend::addGift, "生日礼物", "迪奥烈焰蓝金") .with(GirlFriend::addGift, "纪念日礼物", "阿玛尼红管唇釉") // 等等等等 ... .build(); } }
看到了吗!实例化和属性设置在同一条语句执行,链式操作,一路点点点,清爽!
Talk is cheap, show me the code:
/** * 通用的 Builder 模式构建器 * *@author: CipherCui *@since2019/8/29 */ public class Builder<T>{ private final Supplier<T> instantiator; private List<Consumer<T>> modifiers = new ArrayList<>(); public Builder(Supplier<T> instantiator){ this.instantiator = instantiator; } public static <T> Builder<T>of(Supplier<T> instantiator){ return new Builder<>(instantiator); } public <P1> Builder<T>with(Consumer1<T, P1> consumer, P1 p1){ Consumer<T> c = instance -> consumer.accept(instance, p1); modifiers.add(c); return this; } public <P1, P2> Builder<T>with(Consumer2<T, P1, P2> consumer, P1 p1, P2 p2){ Consumer<T> c = instance -> consumer.accept(instance, p1, p2); modifiers.add(c); return this; } public <P1, P2, P3> Builder<T>with(Consumer3<T, P1, P2, P3> consumer, P1 p1, P2 p2, P3 p3){ Consumer<T> c = instance -> consumer.accept(instance, p1, p2, p3); modifiers.add(c); return this; } public T build(){ T value = instantiator.get(); modifiers.forEach(modifier -> modifier.accept(value)); modifiers.clear(); return value; } /** * 1 参数 Consumer */ @FunctionalInterface public interface Consumer1<T,P1>{ void accept(T t, P1 p1); } /** * 2 参数 Consumer */ @FunctionalInterface public interface Consumer2<T,P1,P2>{ void accept(T t, P1 p1, P2 p2); } /** * 3 参数 Consumer */ @FunctionalInterface public interface Consumer3<T,P1,P2,P3>{ void accept(T t, P1 p1, P2 p2, P3 p3); } }
这个示例最多支持三个参数的设置属性方法,也完全够用了。如果要扩展也很容易,依葫芦画瓢,添加多个参数的 Consumer
。
快用你的 Builder 建个对象吧~