NullPointerException and OneToMany Eager Fetch-CodePudding

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();
}

CodePudding user response：

I think it's because you named a class but did not set an instance in memory of that class, because having this in your code is the same as = null:

private BudgetPlan budgetPlan;

So when your code executes with budgetPlan.berechnePrognose(); it cannot allocate anything in the memory.

Try:

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

Disclaimer: I have no experience with all the annotations in there, so maybe I'm missing the logic of this entire code but just make sure BudgetPlan budgetPlan != null.

CodePudding user response：

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();
}