复合id类的hashCode（）和equals（）方法

Question

我一直试图找到实现复合id类的equals（）和hashCode（）方法的正确方法。

我尝试更新主要对象（Gara）时遇到的麻烦是：

1. 的StackOverflow
2. DuplicateKeyException：具有相同标识符值的其他对象已与会话
关联
3. org.hibernate.ObjectNotFoundException：不存在具有给定标识符的行

我的Composite-id类

@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
                + "]";
    }


}

Answer 1

这些看起来效果很好：

 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;
    }