Lombok的@Data生成的hashCode和equals方法坑

一、場景復現

創建兩個lombok的@Data註解的類Pig實例，放進HashMap當key，map裏面的數據居然被覆蓋了。

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;
}

運行結果：

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，明明沒有重寫hashcode和equals方法，卻返回true

 

通過反編譯生成的class，可以看得lombok幫類文件生成hashcode和equals方法。hashcode和equals方法使用類聲明的所有屬性方法生成的（不包含繼承的父類屬性方法）

//
// 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、解決方案

（1）不使用lombok對子類進行生成屬性方法

（2）lombok生成屬性方法的子類不能使用map、set等集合使用的hashcode和equals方法。