[FIXED] NullPointerException and OneToMany Eager Fetch

Issue

In a Service I want to set the betrag for a BudgetGeschaeftfeld. After setting the Betrag, a method of budgetPlan which is Fetch.Eager should be called to update its own Betrag. However I get a NullPointerException

java.lang.NullPointerException: Cannot invoke "com.bm.ent.budgetplan.BudgetPlan.berechnePrognose()" because "this.budgetPlan" is null

why is this happening? and what can I do to solve it?

my Class code:

@Entity(name= "Budgetgeschaftsfeld")
@Getter
@Setter
@NoArgsConstructor
public class BudgetGeschaeftsfeld extends Budget{
@JsonIgnore
@OneToMany(
        mappedBy="budgetGeschaftfeld",
        cascade=CascadeType.ALL,
        orphanRemoval=true,
        targetEntity = BudgetMarke.class
        )
private List<BudgetMarke> childBudgets= new ArrayList<>();

@JsonIgnore
@ManyToMany
@ToString.Exclude
private List<User> users= new ArrayList<>();

@JsonIgnore
@ManyToOne( fetch=FetchType.EAGER,
        cascade=CascadeType.PERSIST)
@JoinColumn(name="pid")
@ToString.Exclude
private BudgetPlan budgetPlan;

public BudgetGeschaeftsfeld(String name, BudgetTyp typ, Double betrag, String kommentar) {
    super(name, typ, betrag, kommentar);
}


public void setBetrag(Double betrag) {
    if (this.getBudgetTyp()==BudgetTyp.DYNAMISCH) {
        super.setBetrag(this.betragChildBudgets());
    }else {
     super.setBetrag(betrag);   
    }
    budgetPlan.berechnePrognose();
}

Solution

The answer was

@JsonIgnore
@ManyToOne( fetch=FetchType.Lazy,
    cascade=CascadeType.PERSIST)
@JoinColumn(name="pid")
@ToString.Exclude
private BudgetPlan budgetPlan;

and then getting the budgetplan before calling the method

public void setBetrag(Double betrag) {
    if (this.getBudgetTyp()==BudgetTyp.DYNAMISCH) {
        super.setBetrag(this.betragChildBudgets());
    }else {
     super.setBetrag(betrag);   
    }
    detBudgetPlan().berechnePrognose();
}

Answered By - Nortap
Answer Checked By - David Goodson (JavaFixing Volunteer)