Question

我有一个错误，让我疯了。当我尝试创建一个新对象时，Hibernate会返回一个错误：

对象引用未保存的瞬态实例 - 在刷新之前保存瞬态实例：EquipmentType;嵌套异常是org.hibernate.TransientObjectException：object引用未保存的瞬态实例 - 保存瞬态实例

我有以下Spring服务：

CommandService

public class CommandService implements ICommandService {
    @Override
    public Command createCommand(String name, String eqpName) {
        Command cmd = new Command();        
        Equipment eqp = getEquipment(eqpName);

        cmd.setEquipment(eqp);      
        cmd.setName(name);

        return cmd;
    }

    @Override
    public Equipment getEquipment(String eqpName) {
        IEquipmentService eqpService = (IEquipmentService) SPRING_CONTEXT.getBean("EquipmentService");

        Equipment eqp = eqpService.findEquipmentByName(eqpName);

        EquipmentType eqpType = new EquipmentType();
        eqpType.setName("MyType");
        eqp.setType(eqpType);

        Model model = new Model();
        model.setName("MyModel");
        eqp.setModel(model);

        eqpService.saveEquipment(eqp);

        return eqp;     
    }
}

EquipmentService

public class EquipmentService implements IEquipmentService {

    private DAO dao; // This DAO is autowired

    @Override
    public void saveEquipment(Equipment eqp) {
        completeModel(eqp);
        completeEqpType(eqp);

        ((EquipmentDAO) dao).merge(eqp);
    }

    private void completeModel(Equipment eqp) {
        IModelService modelService = (IModelService) SPRING_CONTEXT.getBean("ModelService");
        Model result = modelService.findModelByName(eqp.getModel().getName());  // Fails here

        eqp.setModel(result);
    }

    private void completeEqpType(Equipment eqp) {
        IEquipmentTypeService eqpTypeService = (IEquipmentTypeService) SPRING_CONTEXT.getBean("EquipmentTypeService");
        EquipmentType result = eqpTypeService.findEquipmentTypeByName(eqp.getType().getName());

        eqp.setType(result);
    }
}

请注意，IEquipmentService和ICommandService的所有方法都配置为事务性的。我的对象Equipment由Model和EquipmentType组成。这些对象引用数据库中已经创建的对象，这就是为什么我不想再次保存它们。

这是Hibernate配置：

<class name="Equipment" table="equipment" lazy="false">
        <id name="equipmentId" type="java.lang.Integer">
            <column name="EQUIPMENT_ID" />
            <generator class="native" />
        </id>
        <many-to-one name="type" class="EquipmentType" fetch="join" not-null="true">
            <column name="TYPE_ID" not-null="true" />
        </many-to-one>
        <many-to-one name="model" class="Model" fetch="join" not-null="true">
            <column name="MODEL_ID" not-null="true" />
        </many-to-one>
</class>

编辑：根据要求，以下是方法equals(..)和hashcode(..)

装备

@Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((equipmentId == null) ? 0 : equipmentId.hashCode());
    result = prime * result + ((type == null) ? 0 : type.hashCode());
    result = prime * result + ((model == null) ? 0 : model.hashCode());
    return result;
}

@Override
public boolean equals(Object obj) {
    if (obj == this) {
        return true;
    }

    if (obj instanceof Equipment) {
        Equipment eqp = (Equipment) obj;
        return new EqualsBuilder().append(this.equipmentId, eqp.getEquipmentId()).isEquals();
    }

    return false;
}

对于Model和EquipmentType，未明确定义这些方法。

我可以帮助我弄清楚为什么在拨打createCommand(..)时会返回此错误？

Answer 1

我认为问题是您在EquipmentType方法中设置了新的Model和getEquipment。由于您还没有在这两个类中定义equals（）和hashcode方法，因此hibernate无法将这些与已持久化的对象进行比较。它将它们视为分离（因为equals（）和hashcode（）方法指示新对象而不是现有对象）。这就是为什么它要求您首先保存设备类型和模型对象。

我认为你应该重写equals（）＆amp; hashcode（）正确地在EquipmentType＆amp;模型。

修改

我认为你不应该在completeType（）方法中再次覆盖它时添加新的EquipmentType。为什么不将您的API更改为

EquipmentService#saveEquipment(Equipment e, Sting type, String modelName){
    EquipmentType t = findType();
    Model m = findModel();
    e.setType(t);
    e.setModel(m);
}

如果您无法更改API，则必须先触发新类型和模型，然后再触发hibernate flush。

从数据库加载对象时的TransientObjectException

1 个答案: