I just want to use entity values not to update from other entity

Question

I am using spring boot rest api, data jpa, I just want to use event class and not to update from person class. Following are entity classes,

 @Entity
 @Table(name = "person")
 public class Person {
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
 private Integer person_id;
 private Integer age;
 String first_name;
 String last_name;
 @ManyToMany(fetch = FetchType.LAZY,
        cascade = {
            CascadeType.PERSIST,
            CascadeType.MERGE
        })
  @JoinTable(name = "person_event",
        joinColumns = { @JoinColumn(name = "person_id") },
        inverseJoinColumns = { @JoinColumn(name = "event_id") })
  private Set<Event> event;
   }

Event class is

    @Entity
    @Table(name = "event")
    public class Event {

   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)

   private Integer event_id;
   private String event_date;
   private String title;
    }

I am adding the values from postman as json string, I want to add the event values from event entity, But I dont want to update those values from person entity. From person entity I just want to use the event id but I dont want to update the event table.

    {
    "age": 32,
    "first_name": "Srinath",
    "last_name": "murugula",
    "event": [
        {
            "event_id": 1
        },
        {
            "event_id": 3
        }
      ]
     }

The above string is to adding the person but also updating the other fields of entity class(ie, event_date and title as null.Because I am not mentioning those fields.In Person class I just want use id but dont want to update event table fields.

Answer 1

You can use:

@Cascade({CascadeType.SAVE_UPDATE})

https://mkyong.com/hibernate/cascade-jpa-hibernate-annotation-common-mistake/

Answer 2

I have used:

@Cascade({CascadeType.Detach})

It solved my problem. Working fine.