Hibernate @ManyToOne of an entity with @IdClass

Question

I just added a new entity to my project and now it doesn't start. I think it is related to having a @ManyToOne being part of a composite key but I'm not sure. I reduced my problem to the following entities:

A.class:

@Table(name = "A")
@Entity
@IdClass(KeyA.class)
public class A {
    
   @Id
   private String aId;
    
   @Id
   @ManyToOne
   private B b;
    
   public String getaId() {
      return aId;
   }
    
   public void setaId(String aId) {
      this.aId = aId;
   }
    
   public B getB() {
      return b;
   }
    
   public void setB(B b) {
      this.b = b;
   }
}

B.class:

@Table(name = "B")
@Entity
@IdClass(KeyB.class)
public class B {
    
   @Id
   String bId;
    
   @Id
   String bId2;
    
   public String getbId() {
      return bId;
   }
    
   public void setbId(String bId) {
      this.bId = bId;
   }
    
   public String getbId2() {
      return bId2;
   }
    
   public void setbId2(String bId2) {
      this.bId2 = bId2;
   }
}

KeyA.class:

public class KeyA implements Serializable {
    
   private String aId;
   private String b;
}

KeyB.class

public class KeyB implements Serializable{
    
   public String bId;
   public String bId2;
}

Exception thrown:

        Error creating bean with name 'entityManagerFactory' defined in class path resource
        [...]
        Caused by: org.hibernate.HibernateException: Unable to instantiate default tuplizer [org.hibernate.tuple.component.PojoComponentTuplizer]
    [...]
    Caused by: java.lang.reflect.InvocationTargetException: null
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_201]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_201]
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_201]
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_201]
        at org.hibernate.tuple.component.ComponentTuplizerFactory.constructTuplizer(ComponentTuplizerFactory.java:104) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
        ... 43 common frames omitted
    Caused by: org.hibernate.PropertyNotFoundException: Could not locate field name [bId] on class [java.lang.String]
        at org.hibernate.internal.util.ReflectHelper.findField(ReflectHelper.java:371) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
        at org.hibernate.property.access.internal.PropertyAccessFieldImpl.<init>(PropertyAccessFieldImpl.java:34) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
        at org.hibernate.property.access.internal.PropertyAccessStrategyFieldImpl.buildPropertyAccess(PropertyAccessStrategyFieldImpl.java:26) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
        at org.hibernate.mapping.Property.getGetter(Property.java:311) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]
        at org.hibernate.tuple.component.PojoComponentTuplizer.buildGetter(PojoComponentTuplizer.java:141) ~[hibernate-core-5.4.12.Final.jar:5.4.12.Final]

I tried everything, including importing latest javassist. I'm running Spring Boot 2.2.5.RELEASE on Java 1.8 (it also happens in 11)

Answer 1

Your composite key of A

public class KeyA implements Serializable {

    private String aId;
    private String b;
}

is structured as if B would have only a single string ID (here referred to as b) while in reality it has a composite key itself

public class KeyB implements Serializable{

    public String bId;
    public String bId2;
}

so you have to change KeyA to represent that relationship correctly:

public class KeyA implements Serializable {

    private String aId;
    private KeyB keyB;
}