TransientObjectException when loading an object from database

Question

I have an error that makes me go nuts. When I try to create a new object, Hibernate returns an error :

object references an unsaved transient instance - save the transient instance before flushing: EquipmentType; nested exception is org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before

I have the following Spring services :

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);
    }
}

Note that all the methods of IEquipmentService and ICommandService are configured as transactional. My object Equipment is composed of a Model and an EquipmentType. Those objects refer already created objects in database, that is why I don't want to save them again.

Here is the Hibernate configuration :

<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>

EDIT : As requested, here are the methods equals(..) and hashcode(..)

For Equipment

@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;
}

For Model and EquipmentType, those methods are not explicitly defined.

Can you help me to figure out why this error is returned when I call createCommand(..) ?

How have you defined equals() and hashcode() method for your model classes? Can you add those in question details. — Mohit
– Mohit, Commented Nov 27, 2015 at 14:29
@mohit I edited my original post. Note that EqualsBuilder is provided by Apache Commons. — dounyy
– dounyy, Commented Nov 27, 2015 at 14:40

Mohit · Accepted Answer · 2015-11-27 15:17:08Z

1

I think the problem is that you set new EquipmentType and Model in your getEquipment method. As you haven't defined equals() and hashcode method in these 2 classes, hibernate is unable to compare these with already persisted objects. It sees them as detached (because equals() and hashcode() methods are indicating new objects instead of existing objects). That's why it ask you to save equipment type and model objects first.

I think you should override equals() & hashcode() properly in EquipmentType & Model.

EDIT

I think you shouldn't add new EquipmentType as you override it again in completeType() method. Why don't you change your API to

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

If you can't change APIs, you will have to persist new type and model first before hibernate flush is triggered.

edited Nov 27, 2015 at 15:17

answered Nov 27, 2015 at 14:56

Mohit

1,7551 gold badge15 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

dounyy Over a year ago

But my equals() methods would compare the IDs of those objects. In getEquipment(), my objects don't have any ID, so they would still be considered as detached, would they ?

Mohit Over a year ago

New objects remain detached as you are not saving them before flush is triggered. Flush is automatically triggered whenever select query is executed. I have edited the answer to give a work-around.

dounyy Over a year ago

What I don't understand is, why does hibernate has to flush if the transaction is not ended yet ?

Mohit Over a year ago

Hibernate doesn't always flush at transaction commit. If hibernate has to run a select, it must first sync all in memory changes with databases so that in memory objects can also appear in search result.

dounyy Over a year ago

So you are telling me there is no way to create a Java object and then perform a select on the database without persisting that object ? Isn't that weird ?

|

Collectives™ on Stack Overflow

TransientObjectException when loading an object from database

1 Answer 1

8 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

8 Comments

Your Answer

Sign up or log in

Post as a guest

Related