Spring data jpa : One to one Relationship

Question

I have Sensor Entity has Relationship to Location Entity

@RequiredArgsConstructor @Data public class TemperatureSensor { @Id @GeneratedValue(strategy = AUTO) private Long id; private float temperature; private float min; private float max; private float timeInterval; private boolean activityState; @OneToOne private Location location; }

@Entity @Data @RequiredArgsConstructor public class Location { @Id @GeneratedValue(strategy = AUTO) private Long id; private Long coordinates; private String name; private EnvironmentState environmentState = EnvironmentState.NORMAL_CASE; @OneToOne private TemperatureSensor temperatureSensor; }

I created two endpoints to initiate each entity, so I send Sensor object using Postman like this and get location_id null in the database. The same is happening with Location.

 { "temperature" : "15.2", "min" :"9.0", "max" : "20.0", "timeInterval" : "552.5", "activityState" : "true", "location_id" :"1" }

Also, I tried to send location object and I got the exception: object references an unsaved transient instance - save the transient instance before flushing

{ "temperature" : "15.2", "min" :"9.0", "max" : "20.0", "timeInterval" : "552.5", "activityState" : "true", "location" :{"coordinates": "123","name" : "loc01"} }

João Dias · Accepted Answer · 2021-09-30 22:00:42Z

The issue seems to be that you are missing cascade options on your @OneToOne annotations. Try using @OneToOne(cascade = CascadeType.ALL) instead (this will cascade all operations PERSIST, MERGE, REMOVE, REFRESH, DETACH to the other entity).

@RequiredArgsConstructor @Data public class TemperatureSensor { @Id @GeneratedValue(strategy = AUTO) private Long id; private float temperature; private float min; private float max; private float timeInterval; private boolean activityState; @OneToOne(cascade = CascadeType.ALL) private Location location; }

Entity @Data @RequiredArgsConstructor public class Location { @Id @GeneratedValue(strategy = AUTO) private Long id; private Long coordinates; private String name; private EnvironmentState environmentState = EnvironmentState.NORMAL_CASE; @OneToOne(cascade = CascadeType.ALL) private TemperatureSensor temperatureSensor; }

Thanks, it works! but I still need to pass the whole object. how can I pass only the foreign key
To my knowledge, there is no way to have that automated. If the given location_id already exists, then you need to actively retrieve it from the database and set it to the received TemperatureSensor. Unless you want to have a custom persist query for your TemperatureSensor but I am not sure that is the best option.

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