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POJPA - Persisting a One to Many relationship
 

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    <p>Maybe this is a stupid question but it's bugging me.</p> <p>I have a bi-directional one to many relationship of Employee to Vehicles. When I persist an Employee in the database for the first time (i.e. it has no assigned ID) I also want its associated Vehicles to be persisted. </p> <p>This works fine for me at the moment, except that my saved Vehicle entity is not getting the associated Employee mapped automatically, and in the database the employee_id foreign key column in the Vehicle table is null.</p> <p>My question is, is it possible to have the Vehicle's employee persisted at the same time the Employee itself is being persisted? I realise that the Employee would need to be saved first, then the Vehicle saved afterwards. Can JPA do this automatically for me? Or do I have to do something like the following:</p> <pre><code>Vehicle vehicle1 = new Vehicle(); Set&lt;Vehicle&gt; vehicles = new HashSet&lt;Vehicle&gt;(); vehicles.add(vehicle1); Employee newEmployee = new Employee("matt"); newEmployee.setVehicles(vehicles); Employee savedEmployee = employeeDao.persistOrMerge(newEmployee); vehicle1.setAssociatedEmployee(savedEmployee); vehicleDao.persistOrMerge(vehicle1); </code></pre> <p>Thanks!</p> <p>Edit: As requested, here's my mappings (without all the other methods etc.)</p> <pre><code>@Entity public class Employee { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name="employee_id") private Long id; @OneToMany(mappedBy="associatedEmployee", cascade=CascadeType.ALL) private Set&lt;Vehicle&gt; vehicles; ... } @Entity public class Vehicle { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name="vehicle_id") private Long id; @ManyToOne @JoinColumn(name="employee_id") private Employee associatedEmployee; ... } </code></pre> <p>I just realised I should have had the following method defined on my Employee class:</p> <pre><code>public void addVehicle(Vehicle vehicle) { vehicle.setAssociatedEmployee(this); vehicles.add(vehicle); } </code></pre> <p>Now the code above will look like this:</p> <pre><code>Vehicle vehicle1 = new Vehicle(); Employee newEmployee = new Employee("matt"); newEmployee.addVehicle(vehicle1); Employee savedEmployee = employeeDao.persistOrMerge(newEmployee); </code></pre> <p>Much simpler and cleaner. Thanks for your help everyone!</p>
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