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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;@Datapublic 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
   
     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;@Datapublic abstract class Animal {    private String name;    private String color;}

运行结果：

map.size():1map.get(aPig):2map.get(bPig):2map.keySet().iterator().next().getName():AaPig.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() + ")";    }}

二、解决方案

（1）不使用lombok对子类进行生成属性方法

（2）lombok生成属性方法的子类不能使用map、set等集合使用的hashcode和equals方法。

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