Hibernate exception PropertyNotFoundException when using Transformer

Question

I'm using hibernate and hql for querying in my Java codes. But I got an exception like this:

Caused by: org.hibernate.PropertyNotFoundException: Could not find setter for 0 on class [my class]
    at org.hibernate.property.ChainedPropertyAccessor.getSetter(ChainedPropertyAccessor.java:44)

I don't understand what the "0" means. Here are some deatils with examples:

I have several tables joining hql. The tables are like this:

A
- A_ID
- NAME

B
- B_ID
- A_ID

C
- C_ID
- B_ID
- LENGTH
- UNIT

Classes:

@Entity
@Table(name="A")
class A
{
    @Id
    @Column(name="A_ID", updatable=false)
    private Long id;

    @Column(name="NAME", nullable=false, length=10, updatable=false)
    private String name;

    @OneToMany(mappedBy="a", fetch=FetchType.LAZY, cascade={CascadeType.ALL})
    @JoinColumn(name="A_ID", nullable=false)
    private Set<B> bs;

    @Transient
    private Double length;

    @Transient
    private String unit;

    // Setters and getters
    ...
}

@Entity
@Table(name="B")
class B
{
    @Id
    @Column(name="B_ID", updatable=false)
    private Long id;

    @ManyToOne
    @JoinColumn(name="A_ID", nullable=false, insertable=true, updatable=false)
    private A a;

    @OneToMany(mappedBy="b", fetch=FetchType.LAZY, cascade={CascadeType.ALL})
    @JoinColumn(name="B_ID", nullable=false)
    private Set<C> cs;

    // Setters and getters
    ...
}

@Entity
@Table(name="C")
class C
{
    @Id
    @Column(name="C_ID", updatable=false)
    private Long id;

    @ManyToOne
    @JoinColumn(name="B_ID", nullable=false, insertable=true, updatable=false)
    private B b;

    @Column(name="LENGTH", nullable=false, updatable=false)
    private Double length;

    @Column(name="UNIT", nullable=false, length=10, updatable=false)
    private String unit;

    // Setters and getters
    ...
}

hql:

select a, sum(c.length) as length, min(c.unit) as unit
from A a
left outer join a.b as b
left outer join b.c as c
group by
a.id
a.name

Query:

Query query = session.createQuery(hql.toString()).setResultTransformer(Transformers.aliasToBean(A.class));

The result is a list of object "A" with the length and unit collected. I don't understand why I got this exception. Please give some advices.

---

Update:

I wrote a ResultTransformer and output all the "alias" to see the problem:

-> 0
-> length
-> unit

It seems it treats the "A" besides with length and unit. There should be some problems with my HQL?

Answer 1

Problem found:

Even if the HQL can be translated to sql correctly, but when ResultTransformer gets the result, there will be only 3 fields in the result:

1. A
2. length
3. unit

No matter how many fields in A, they will be aggregated into a single field "A" and since I didn't set any alias to this field, it will be treated as "field 0".

So the problem solved after I changed the HQL like this:

select a.id as id, a.name as name, sum(c.length) as length, min(c.unit) as unit
from A a
left outer join a.b as b
left outer join b.c as c
group by
a.id
a.name

Answer 2

@Access(AccessType.FIELD)

add getter and setter of every field

 @Entity
    @Table(name="A")
    @Access(AccessType.FIELD)
    class A
    {
        @Id
        @Column(name="A_ID", updatable=false)
        private Long id;

       public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id= id;
    }
}