JSON parse error: Already had POJO for id

[Nathan Milota]

I'm getting this error in Angular for my Spring Boot project.  

JSON parse error: Already had POJO for id (java.lang.Long) [[ObjectId: key=5, type=com.fasterxml.jackson.databind.deser.impl.PropertyBasedObjectIdGenerator, scope=com.km.theatretix.entity.Venue]]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Already had POJO for id (java.lang.Long) [[ObjectId: key=5, type=com.fasterxml.jackson.databind.deser.impl.PropertyBasedObjectIdGenerator, scope=com.km.theatretix.entity.Venue]] (through reference chain: com.km.theatretix.entity.Ticket["theatreEvent"]->com.km.theatretix.entity.TheatreEvent["venue"]->com.km.theatretix.entity.Venue["id"])

However, it only happens on the first loop when I try to create a new ticket.   Here is the Angular function.  

 createTickets(){    let isClear: boolean=true;  //This boolean will stay true unless there is a ticket already added to the database right before the customer selects them.        if(this.ticketPriceList.length===this.seatSelection.length){      //If there is not an option clicked on for each seat (e.g Adult/Child, the code will not execute to avoid any null values entered.)                this.ticketService.getTicketsByEventId(this.theatreEvent.id).subscribe(          params=>{            this.ticketList=params;            //This gets all the tickets for this current event so it can be verified below that there are no other users who selected the same seats            //right before them before the screen had time to refresh showing those seats as occupied.            for(let i=0; i<this.seatSelection.length; i++){   //************Error is only happening on the first iteration of this loop.************                          for(let o=0; o<this.ticketList.length; o++){                  for(let x=0; x<this.seatSelection.length; x++){             if(this.seatSelection[x].section===this.ticketList[o].seat.section && this.seatSelection[x].row===this.ticketList[o].seat.row && this.seatSelection[x].seatNumber===              this.ticketList[o].seat.seatNumber){                //If the multiple customers are trying to book the same seats at the same time, it will stop this from adding the same seat to multiple tickets and reload the page if                //one customer selects tickets after another had already completed the selection for the same seats.                  isClear=false;                  alert("Something went wrong!  Please try again!");                  window.location.reload();                  break;                }              }            }                if(isClear===true){  //isClear will stay true as long as the seats the customer selects have not been added to a ticket.                  let ticket= new Ticket();                    ticket.isAdmitted=false;                  ticket.purchasedStatus= "Not Purchased"; //The next screen will give them five minutes to finish their checkout and this will be updated to 'Purhased'.                  //If they don't complete the checkout the ticket will be deleted from the database and the seat will update back to available.                  ticket.seat=this.seatSelection[i];                  ticket.theatreEvent= this.theatreEvent;                  for(let x=0; x<this.ticketPriceList.length; x++){              //The if statement below will only return a maximum of one value                    if(this.seatSelection[i].section===this.ticketPriceList[x].seat.section && this.seatSelection[i].row===this.ticketPriceList[x].seat.row &&                      this.seatSelection[i].seatNumber===this.ticketPriceList[x].seat.seatNumber){                      ticket.price=this.ticketPriceList[i].price;                      ticket.admissionType= this.ticketPriceList[i].ticketType;                    }                  }                                  this.ticketService.addTicket(ticket).subscribe(                    params=>console.log(params)                  )                }                          }          } )          }    else{      alert("Please select a type for all your selected seats before proceeding");    }  }

Here is the Java code for the entity where the error is happening.  

public class TheatreEvent {

	@Id
	@GeneratedValue
	private long id;
	
	private String name;
	
	@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property="id", scope=Venue.class)//Error is happening here. 
	@ManyToOne
	@JoinColumn(name="venue_id", referencedColumnName="id", nullable=false)
	private Venue venue;
	
	@JsonIgnore
	@OneToMany(mappedBy="theatreEvent")
	private List<Ticket> tickets;
	


	@DateTimeFormat(pattern = "yyyy-MM-dd hh:mm:ss")
	@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "CST")
	private Date date;
	
}

	

[Nathan Milota]

It does it only for the first item in the seat table of the database.  Every other seat in the database works just fine.   It is just one seat that won't work right.  I don't get what's wrong.

[Martin Keller]

Have you found a solution. Currently I'm facing the same problem...

[Martin Keller]

Honestly I've fixed it. Maybe the solution helps you or some other one.
This link Spring Custom Serializers with @JsonIdentityInfo helped me to figure out what possibly could help.

To explain my general conditions.

I had a circling relationship between objects:

@JsonIdentityInfo(
      generator = ObjectIdGenerators.PropertyGenerator.class,
      property = "id")
Object A
- Id
- Object B
- Object C

@JsonIdentityInfo(
      generator = ObjectIdGenerators.PropertyGenerator.class,
      property = "id")
Object B
- Id
- List<Object A>

@JsonIdentityInfo(
      generator = ObjectIdGenerators.PropertyGenerator.class,
      property = "id")
Object C
- Id
- List<Object A>

Just had problems with the first entry as you've mentioned.
For me the solution was putting a "scope = Classname.class" additionally to every DTO class with the @JsonIdentityInfo. So it looked like this:

@JsonIdentityInfo(
      generator = ObjectIdGenerators.PropertyGenerator.class,
      property = "id",
      scope = Object_A.class)
Object_A
- Id
- Object_B
- Object_C

@JsonIdentityInfo(
      generator = ObjectIdGenerators.PropertyGenerator.class,
      property = "id",
      scope = Object_B.class)
Object_B
- Id
- List<Object_A>

@JsonIdentityInfo(
      generator = ObjectIdGenerators.PropertyGenerator.class,
      property = "id",
      scope = Object_C.class)
Object_C
- Id
- List<Object_A>

Maybe it helps someone who struggles with this issue too