Spring Jpa Specification and Eager loading - spring

Question

How can i get list of tiket with its categories through Jpa Specification
Example model:
#Entity
#Table(name = "tickets")
public class Ticket {
#Id
private Integer id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "category_id")
private Category
}
Method of service:
public Page<Ticket> findAll(Pageable pageable) {
return ticketRepository.findAll((root, query, cb) -> {
root.join("category");
return query.getRestriction();
}, pageable);
}

Answer 1

I was able to eager load the collection by using a fetch instead of a join.
public Page<Ticket> findAll(Pageable pageable) {
return ticketRepository.findAll((root, query, cb) -> {
root.fetch("category");
return query.getRestriction();
}, pageable);
}
The fetch method will use the default join type (inner). If want to load tickets with no category, you'll have to pass JoinType.LEFT as the second parameter.

Answer 2

as they say, stackoverflow giveth, stackoverflow taketh..
I took this class off SO quite some time ago, feel free to recycle it..
import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.Collection;
import org.apache.commons.beanutils.PropertyUtils;
import org.hibernate.Hibernate;
public class BeanLoader {
/**
* StackOverflow safe, if called before json creation, cyclic object must be avoided
*/
public static void eagerize(Object obj) {
if(!Hibernate.isInitialized(obj))
Hibernate.initialize(obj);
PropertyDescriptor[] properties = PropertyUtils.getPropertyDescriptors(obj);
for (PropertyDescriptor propertyDescriptor : properties) {
Object origProp = null;
try {
origProp = PropertyUtils.getProperty(obj, propertyDescriptor.getName());
} catch (IllegalAccessException e) {
// Handled, but hopefully dead code
origProp=null;
} catch (InvocationTargetException e) {
// Single catch for obsolete java developers!
origProp=null;
} catch (NoSuchMethodException e) {
// Single catch for obsolete java developers!
origProp=null;
}
if (origProp != null
&& origProp.getClass().getPackage().toString().contains("domain")) {
eagerize(origProp, new ArrayList<String>());
}
if (origProp instanceof Collection) {
for (Object item : (Collection) origProp) {
if (item.getClass().getPackage().toString().contains("domain")){
eagerize(item, new ArrayList<String>());
}
}
}
}
}
/**
* StackOverflows if passed a bean containing cyclic fields. Call only if sure that this won't happen!
*/
public static void eagerizeUnsafe(Object obj) {
if(!Hibernate.isInitialized(obj))
Hibernate.initialize(obj);
PropertyDescriptor[] properties = PropertyUtils.getPropertyDescriptors(obj);
for (PropertyDescriptor propertyDescriptor : properties) {
Object origProp = null;
try {
origProp = PropertyUtils.getProperty(obj, propertyDescriptor.getName());
} catch (IllegalAccessException e) {
// Handled, but hopefully dead code
origProp=null;
} catch (InvocationTargetException e) {
// Single catch for obsolete java developers!
origProp=null;
} catch (NoSuchMethodException e) {
// Single catch for obsolete java developers!
origProp=null;
}
if (origProp != null
&& origProp.getClass().getPackage().toString().contains("domain")) {
eagerize(origProp);
}
if (origProp instanceof Collection) {
for (Object item : (Collection) origProp) {
if (item.getClass().getPackage().toString().contains("domain")){
eagerize(item);
}
}
}
}
}
private static void eagerize(Object obj, ArrayList<String> visitedBeans) {
if (!visitedBeans.contains(obj.getClass().getName())){
visitedBeans.add(obj.getClass().getName());
} else {
return;
}
if(!Hibernate.isInitialized(obj))
Hibernate.initialize(obj);
PropertyDescriptor[] properties = PropertyUtils.getPropertyDescriptors(obj);
for (PropertyDescriptor propertyDescriptor : properties) {
Object origProp = null;
try {
origProp = PropertyUtils.getProperty(obj, propertyDescriptor.getName());
} catch (IllegalAccessException e) {
// Handled, but hopefully dead code
origProp=null;
} catch (InvocationTargetException e) {
// Single catch for obsolete java developers!
origProp=null;
} catch (NoSuchMethodException e) {
// Single catch for obsolete java developers!
origProp=null;
}
if (origProp != null
&& origProp.getClass().getPackage().toString().contains("domain")) {
eagerize(origProp, visitedBeans);
}
if (origProp instanceof User){
((User) origProp).setRelatedNra(null);
User u=(User) origProp;
if (u.getRelatedMps()!=null)
u.getRelatedMps().clear();
if (u.getRelatedDps()!=null)
u.getRelatedDps().clear();
}
if (origProp instanceof Collection) {
for (Object item : (Collection) origProp) {
if (item.getClass().getPackage().toString().contains("domain")){
eagerize(item, (ArrayList<String>) visitedBeans.clone());
}
}
}
}
}
}
modify it as you see fit.. the method you'll call is "eagerizeUnsafe".
YMMV, but this should to the trick to eagerize all the collections of a lazily initialized bean.