org.hibernate.PropertyAccessException，同时保持ManyToMany关系

Question

Have a problem persisting a ManyToMany relationship mapped like that

Document.java

public class Document {
    .......
    @ManyToMany(targetEntity = Category.class, cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinTable(name = "fideuram_gup_documents_in_categories",
        joinColumns = @JoinColumn(name="fk_document"),
        inverseJoinColumns = @JoinColumn(name = "fk_category"))
    private Set<Category> categories = new HashSet<Category>();
    .......
}

where Category is one more entity of my model which I don't paste here since it doesn't carry a reverse mapping of this relation, and has just an ID and a name.

When I try to persist Document however I get the following error:

org.hibernate.PropertyAccessException: could not get a field value by reflection getter of it.ardesia.fideuram.gup.model.Category.id

I've surfed the web about it but no page relates to ManyToMany relations. Of course all the ManyToOne relations I have on the entity Document work fine.

I'm using:

spring-data-jpa:1.2.0.RELEASE
hibernate-core:4.2.2.Final
hibernate-entitymanager:4.2.2.final

UPDATE

All entities expose a default constructor and getter/setter for every field. Or,more preciselt, I'm using Spring Roo for creating the entity and it injects getters and setters automatically upon compilation.

Answer 1

You can instrument Hibernate how it must access your property using @javax.persistence.Access annotation; put on your mapped class with @Access.value set to

1. AccessType.FIELD for direct field access
2. AccessType.PROPERTY for accessing properties using accessors

Answer 2

Maybe it can help you, I already did the same, I put my code, it creates a join table:

@Entity
@Table(name = "custom_pizza")
public class CustomPizza extends BaseEntity {

private static final long serialVersionUID = 1L;

// ManyToMany instead of oneToMany in order to don't have the unique
// constraint on each primary key of the join table
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "custom_pizza_topping", joinColumns = @JoinColumn(name =  "custom_pizza_id"), inverseJoinColumns = @JoinColumn(name = "topping_id"))
private Set<Topping> toppings = new HashSet<Topping>();

public void addTopping(Topping topping) {
  toppings.add(topping);
}

public void removeTopping(Topping topping) {
  toppings.remove(topping);
}
...

And my topping:

 @Entity
 @Table(name = "topping")
 public class Topping extends BaseEntity {

 private static final long serialVersionUID = 1L;

 @Column(name = "name", nullable = false)
 private String name;

 @Column(name = "price", nullable = false)
 private float price;
 ....

and the BaseEntity

  @MappedSuperclass
  public abstract class BaseEntity implements Serializable {

  private static final long serialVersionUID = 1L;

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  @Column(name = "id")
  private Long id;
  ...