How to fetch child association for an JPA entity

Question

I am looking to build a dynamic framework where and entity object is provided and I will not have any knowledge of current entity type.

What I am trying is, if there are any child associations exist with ManyToOne association and process them differently.

Please let me know is there any way i can find child association names which have ManyToOne relationship

example:

    //Parent Class 
public class Person
{
    @OneToMany(cascade = CascadeType.PERSIST, mappedBy = "personName")
    private List<FamilyName> familyNameList = null;
}

    // Child Class 
public class FamilyName
{
    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)
    @JoinColumn(name = "PERSON_RID", referencedColumnName = "PERSONNAME_RID", nullable = false),
    private PersonNameNonAggregates personName = null;
}

I will be given a method similar as below

private void processEntity(Class<T> persistentClass){
// find child associations of the given persistent class and process 
}

Let me know is there any i can fetch child associations names

The @ManyToOne annotation is retained at runtime. You can check fields/methods if they have this annotation. — toongeorges, Aug 08 '17 at 15:08
@toongeorges is there any way i can fetch whether the given field is annotated with ManyToOne or not. please let me know — Maddy, Aug 08 '17 at 17:19
see https://stackoverflow.com/questions/4296910/is-it-possible-to-read-the-value-of-a-annotation-in-java#4296964 — PCO, Aug 09 '17 at 07:46
@PCO thanks i will look into that seems there is no other option than this — Maddy, Aug 09 '17 at 12:32

Maddy · Accepted Answer · 2017-08-11T06:35:26.700

Guys thanks for the support for those who are looking for help to find the associations of the current entity here is a way entity Manager has a meta model object and you can retrieve the current entity attributes and if it is a association or not

public Set<Attribute> fetchAssociates(){
    Set<Attribute> associations = new HashSet();
    Metamodel model = this.entityManager.getMetamodel();
        EntityType cEntity = model.entity(this.persistentClass);
        System.out.println("Current Entity "+cEntity.getName());
        Set<Attribute> attributes =cEntity.getAttributes();
        for(Attribute att : attributes){
            if(att.isAssociation()){
                associations.add(att);
            }
        }
    return associations;
}

How to fetch child association for an JPA entity

1 Answers1