java - 复合id类的hashCode()和equals()方法

我一直在寻找正确的方法来实现Composite-id类的equals()和hashCode()方法。

尝试更新主要对象(Gara)时遇到的麻烦是:

StackOverflow

DuplicateKeyException:具有相同标识符值的另一个对象已与 session

关联

org.hibernate.ObjectNotFoundException:不存在具有给定标识符的行

我的Composite-id类别

@Embeddable
public class GaraAgenziaId implements Serializable {

    private static final long serialVersionUID = 4934033367128755763L;

    static Logger logger = LoggerFactory.getLogger(GaraAgenziaId.class);

    private Gara gara;

    private Agenzia agenzia;

    @ManyToOne
    public Gara getGara() {
        return gara;
    }

    public void setGara(Gara gara) {
        this.gara = gara;
    }

    @ManyToOne
    public Agenzia getAgenzia() {
        return agenzia;
    }

    public void setAgenzia(Agenzia agenzia) {
        this.agenzia = agenzia;
    }


    @Override
    public String toString() {
        return "GaraAgenziaId [Gara=" + gara + ", agenzia=" + agenzia
                + "]";
    }


}

最佳答案

这些似乎很好地工作:

 public boolean equals(Object o) {
        if (this== o) return true;
        if (o ==null|| getClass() != o.getClass()) return false;

        GaraAgenziaId that = (GaraAgenziaId) o;

        if (gara !=null?!gara.equals(that.gara) : that.gara !=null) return false;
        if (agenzia !=null?!agenzia.equals(that.agenzia) : that.agenzia !=null)
            return false;

        return true;
    }

    public int hashCode() {
        int result;
        result = (agenzia !=null? agenzia.hashCode() : 0);
        result =31* result + (gara !=null? gara.hashCode() : 0);
        return result;
    }