Dealing with deserialization of a complex POJO from a JSON string and persisting it in a MySQL database can be quite challenging. Below is a simplified example class:
@Entity
@Table(name="a")
public class A{
private Long id;
private B b;
private C c;
private D d;
}
@ManyToOne
@JoinColumn(name="b_id")
public B getB(){
return this.b;
}
public void setB(B b){ this.b = b; }
@ManyToOne
@JoinColumn(name="c_id")
public C getC(){
return this.c;
}
public void setC(C c){ this.c = c; }
@ManyToOne
@JoinColumn(name="d_id")
public D getD(){
return this.d;
}
public void setD(D d){ this.d = d; }
The problem arises when dealing with classes B, C, and D that have multiple non-nullable fields and objects, leading to a massive JSON payload for persistence. However, if we only need to persist the deserialized object A, then ideally we would just require the _id fields from B, C, and D.
Currently, the JSON structure looks like:
{
"id":1,
"b":{"id":2, ...},
"c":{"id":3, ...},
"d":{"id":4, ...}
}
where all non-nullable fields need to be filled in. The aim is to simplify the JSON to:
{
"id":1,
"b_id":2,
"c_id":3,
"d_id":4
}
This would allow Hibernate/JPA to update the specified fields in the database directly. It becomes tricky when other parts of the application require the complete object hierarchy except during JSON deserialization where only the _id fields are needed.
Would it be possible to achieve this using JPA/Jackson annotations? Any advice would be greatly appreciated!