How to resolve LazyInitializationException's by always fetching EAGER?

[Dr.Drane]

Hi all,

I'm trying to resolve my LazyInitializationException's by always fetching eagerly.

I've got a bidirectional relationship between my Person and Vehicle classes:

Person with OneToMany to Vehicle:


@Entity
@Table(name = "person")
public class Person {

//Fields
private Long id;
private String name;
private Date birthDate;
private Set<Vehicle> vehicles = new HashSet<Vehicle>();


//Property accessors
@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "id", unique = true, nullable = false)
public Long getId() {
return this.id;
}

public void setId(Long id) {
System.out.println("in java Person-> setId = "+id);
this.id = id;
}

@Column(name = "Name", nullable = false, length = 35)
public String getName() {
return this.name;
}

public void setName(String name) {
System.out.println("in java Person-> setName = "+name);
this.name = name;
}

@Temporal(TemporalType.DATE)
@Column(name = "BirthDate", nullable = true, length = 10)
public Date getBirthDate() {
return this.birthDate;
}

public void setBirthDate(Date birthDate) {
this.birthDate = birthDate;
}

@CollectionOfElements(targetElement = be.tradelec.model.Vehicle.class)
@OneToMany(mappedBy = "person_id", cascade=CascadeType.ALL, fetch=FetchType.EAGER)
public Set<Vehicle> getVehicles() {
return vehicles;
}

public void setVehicles(Set<Vehicle> vehicles) {
System.out.println("in java Person-> setVehicles = "+vehicles);
this.vehicles = vehicles;
}

public void addVehicle(Vehicle vehicle) {
vehicles.add(vehicle);
vehicle.setPerson(this);
}

}


Vehicle with ManyToOne to Peron:


@Entity
@Table(name = "vehicle")
public class Vehicle {

// Fields
private Long id;
private Long person_id;
private Person person;
private String licensePlate;
private String brand;
private String type;

// Constructors
/** default constructor */
public Vehicle() {
}

/** full constructor */
public Vehicle(Long id, Person person,
String licensePlate, String brand, String type) {
this.id = id;
//this.person = person;
this.licensePlate = licensePlate;
this.brand = brand;
this.type = type;
}

// Property accessors
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "id", unique = true, nullable = false)
public Long getId() {
return this.id;
}

public void setId(Long id) {
System.out.println("in java Vehicle-> setIdVehicle = "+id);
this.id = id;
}

@CollectionOfElements(targetElement = be.tradelec.model.Person.class)
@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name = "person_id")
public Person getPerson() {
return this.person;
}

public void setPerson(Person person) {
this.person = person;
}

@Column(name = "LicensePlate", nullable = true, length = 10)
public String getLicensePlate() {
return this.licensePlate;
}

public void setLicensePlate(String licensePlate) {
this.licensePlate = licensePlate;
}

@Column(updatable=false, insertable=false)
public Long getPerson_id() {
return person_id;
}

public void setPerson_id(Long person_id) {
this.person_id = person_id;
}

@Column(name = "Brand", nullable = false, length = 45)
public String getBrand() {
return this.brand;
}

public void setBrand(String brand) {
this.brand = brand;
}

@Column(name = "Type", nullable = false, length = 45)
public String getType() {
return this.type;
}

public void setType(String type) {
this.type = type;
}

}

Saving a Person with added Vehicles works nicely. And with standard fetchtypes I can load my Person (with his vehicles) perfectly.

Now when I try to switch both my mappings to EAGER fetchtypes so I can send the whole Object graph through BlazeDS, I get an error while loading:


Hibernate: select person0_.id as id4_1_, person0_.BirthDate as BirthDate4_1_, person0_.Name as Name4_1_, vehicles1_.person_id as person4_3_, vehicles1_.id as id3_, vehicles1_.id as id5_0_, vehicles1_.Brand as Brand5_0_, vehicles1_.LicensePlate as LicenseP3_5_0_, vehicles1_.person_id as person4_5_0_, vehicles1_.Type as Type5_0_ from person person0_ left outer join vehicle vehicles1_ on person0_.id=vehicles1_.person_id where person0_.id=?
in java Vehicle-> setIdVehicle = 1
in java Person-> setId = 1
in java Vehicle-> setIdVehicle = 2
in java Person-> setName = Jochen
17-jun-2009 10:30:06 org.hibernate.LazyInitializationException <init>
SEVERE: illegal access to loading collection
org.hibernate.LazyInitializationException: illegal access to loading collection
at org.hibernate.collection.AbstractPersistentCollect ion.initialize(AbstractPersistentCollection.java:3 63)
...

[vlad2005]

I don't know if this can be, but why use both annotation, one-to-many and CollectionOfElements. Documentation say that CollectionOfElements it's replacement for one-to-many.
Second, in relation many-to-one, i don't think that it's right to use CollectionOfElements, because in class Vehicle, person it's an object not an collection.
Try to change that, and see how it's work.

[Dr.Drane]

I don't know if this can be, but why use both annotation, one-to-many and CollectionOfElements. Documentation say that CollectionOfElements it's replacement for one-to-many.
Second, in relation many-to-one, i don't think that it's right to use CollectionOfElements, because in class Vehicle, person it's an object not an collection.
Try to change that, and see how it's work.

Oh I see. Makes a lot of sense!
I used collection of elements because I had some kind of problem that seemed like Hibernate not knowing what kind of object I was mapping to. So I used it to make it clear what kind of object I was mapping to. But I think you might be right since it normally is used for non entity to entity mapping I guess.

Will try it tomorrow. Thank you very very much for being so kind to give me some advice! :)

Have a nice day.

Kind regards,

Jochen

[vlad2005]

Probably, u have an bean that instantiate sessionFactory, where u set all hibernate parameters. There need to map and java classes. Personally, i use annotation, because it's more convenient, and i have an tag like this inside sessionFactory bean:


<property name="packagesToScan" value="spa.domain"/>

In this mode, i don't need to map every class. Spring scan for me :).

[vlad2005]

I forgot, but if u want to specify what entity are mapped, u can use "targetEntity" property. Declaration for for @OneToMany it's:


public @interface OneToMany {
Class targetEntity() default void.class;
CascadeType []cascade() default {};
FetchType []fetch() default EAGER;
String mappedBy() default "";
}

Same idea for ManyToOne


public @interface ManyToOne {
Class targetEntity() default void.class;
CascadeType []cascade() default {};
FetchType []fetch() default EAGER;
boolean optional() default true;
}

[Dr.Drane]

w00h00w! Thanks a lot vlad2005!

With you response I managed to solve the issue. :)
Apparently it was associated with me printing out the value of my vehicles variable:


public void setVehicles(Set<Vehicle> vehicles) {
//System.out.println("in java Person-> setVehicles = "+vehicles);

That also explains the "SEVERE: illegal access to loading collection"...i was trying to print out something before it was loaded actually.

And also many thanks for the "packagesToScan" tip!! Very handy since I still was using the annoying-to-manage "annotatedClasses" property:


<property name="annotatedClasses">
<list>
<value>com.prefabsoft.model.Article</value>

So big thumbs up for your help! You made my (fri)day feeling like already being weekend. :)

Greets,

Jochen

[vlad2005]

you're welcome!