Lombok的@Data生成的hashCode和equals方法坑

一、场景复现

创建两个lombok的@Data注解的类Pig实例，放进HashMap当key，map里面的数据居然被覆盖了。

package com.mk;import lombok.Data;
@Data
public class Pig extends Animal{private String sex;
}

package com.mk;import java.util.HashMap;
import java.util.Map;public class TestLombok {public static void main( String[] args ) {Pig aPig = new Pig();aPig.setName("A");aPig.setColor("white");aPig.setSex("male");Pig bPig = new Pig();bPig.setName("B");bPig.setColor("black");bPig.setSex("male");Map<Pig, String> map = new HashMap<>();map.put(aPig, "1");map.put(bPig, "2");System.out.println("map.size():"+map.size());System.out.println("map.get(aPig):"+map.get(aPig));System.out.println("map.get(bPig):"+map.get(bPig));System.out.println("map.keySet().iterator().next().getName():" + map.keySet().iterator().next().getName());System.out.println("aPig.equals(bPig):"+aPig.equals(bPig));}
}

package com.mk;
import lombok.Data;
@Data
public abstract class Animal {private String name;private String color;
}

运行结果：

map.size():1
map.get(aPig):2
map.get(bPig):2
map.keySet().iterator().next().getName():A
aPig.equals(bPig):true

百思不得其解，明明没有重写hashcode和equals方法，却返回true

通过反编译生成的class，可以看得lombok帮类文件生成hashcode和equals方法。hashcode和equals方法使用类声明的所有属性方法生成的（不包含继承的父类属性方法）

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//package com.mk;public abstract class Animal {private String name;private String color;public Animal() {}public String getName() {return this.name;}public String getColor() {return this.color;}public void setName(String name) {this.name = name;}public void setColor(String color) {this.color = color;}public boolean equals(Object o) {if (o == this) {return true;} else if (!(o instanceof Animal)) {return false;} else {Animal other = (Animal)o;if (!other.canEqual(this)) {return false;} else {Object this$name = this.getName();Object other$name = other.getName();if (this$name == null) {if (other$name != null) {return false;}} else if (!this$name.equals(other$name)) {return false;}Object this$color = this.getColor();Object other$color = other.getColor();if (this$color == null) {if (other$color != null) {return false;}} else if (!this$color.equals(other$color)) {return false;}return true;}}}protected boolean canEqual(Object other) {return other instanceof Animal;}public int hashCode() {int PRIME = true;int result = 1;Object $name = this.getName();int result = result * 59 + ($name == null ? 43 : $name.hashCode());Object $color = this.getColor();result = result * 59 + ($color == null ? 43 : $color.hashCode());return result;}public String toString() {return "Animal(name=" + this.getName() + ", color=" + this.getColor() + ")";}
}

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//package com.mk;public class Pig extends Animal {private String sex;public Pig() {}public String getSex() {return this.sex;}public void setSex(String sex) {this.sex = sex;}public boolean equals(Object o) {if (o == this) {return true;} else if (!(o instanceof Pig)) {return false;} else {Pig other = (Pig)o;if (!other.canEqual(this)) {return false;} else {Object this$sex = this.getSex();Object other$sex = other.getSex();if (this$sex == null) {if (other$sex != null) {return false;}} else if (!this$sex.equals(other$sex)) {return false;}return true;}}}protected boolean canEqual(Object other) {return other instanceof Pig;}public int hashCode() {int PRIME = true;int result = 1;Object $sex = this.getSex();int result = result * 59 + ($sex == null ? 43 : $sex.hashCode());return result;}public String toString() {return "Pig(sex=" + this.getSex() + ")";}
}