I create a tree of categories. But when I try to take the root category exception rises. -1 in ParentId field means that this category is root of the tree.

net.sf.hibernate.UnresolvableObjectException: No row with the given identifier exists: -1, of class: org.binarus.domain.PreparationsCategory
at net.sf.hibernate.UnresolvableObjectException.throwIfNull(UnresolvableObjectException.java:38)
at net.sf.hibernate.impl.SessionImpl.internalLoad(SessionImpl.java:1954)
at net.sf.hibernate.type.ManyToOneType.resolveIdentifier(ManyToOneType.java:69)
at net.sf.hibernate.type.EntityType.resolveIdentifier(EntityType.java:204)
at net.sf.hibernate.impl.SessionImpl.initializeEntity(SessionImpl.java:2205)
at net.sf.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:315)
at net.sf.hibernate.loader.Loader.doQuery(Loader.java:305)
at net.sf.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:133)
at net.sf.hibernate.loader.Loader.loadEntity(Loader.java:911)
at net.sf.hibernate.loader.Loader.loadEntity(Loader.java:931)
at net.sf.hibernate.loader.EntityLoader.load(EntityLoader.java:59)
at net.sf.hibernate.loader.EntityLoader.load(EntityLoader.java:51)
at net.sf.hibernate.persister.EntityPersister.load(EntityPersister.java:419)
at net.sf.hibernate.impl.SessionImpl.doLoad(SessionImpl.java:2117)
at net.sf.hibernate.impl.SessionImpl.doLoadByClass(SessionImpl.java:1991)
at net.sf.hibernate.impl.SessionImpl.internalLoad(SessionImpl.java:1953)
at net.sf.hibernate.type.ManyToOneType.resolveIdentifier(ManyToOneType.java:69)
at net.sf.hibernate.type.EntityType.resolveIdentifier(EntityType.java:204)
at net.sf.hibernate.impl.SessionImpl.initializeEntity(SessionImpl.java:2205)
at net.sf.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:315)
at net.sf.hibernate.loader.Loader.doQuery(Loader.java:305)
at net.sf.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:133)
at net.sf.hibernate.loader.Loader.doList(Loader.java:1033)
at net.sf.hibernate.loader.Loader.list(Loader.java:1024)
at net.sf.hibernate.loader.SQLLoader.list(SQLLoader.java:92)
at net.sf.hibernate.impl.SessionImpl.findBySQL(SessionImpl.java:3806)
at net.sf.hibernate.impl.SQLQueryImpl.list(SQLQueryImpl.java:52)


Here my mapping
<class name="org.binarus.domain.PreparationsCategory" table="PreparationsCategories">
<id name="id" column="ID" unsaved-value="-1">
<generator class="increment"/>
</id>
<property name="name" column="Name"/>
<set name="childCategories"
inverse="true"
cascade="all"
order-by="Name ASC">
<key column="ParentID"/>
<one-to-many class="org.binarus.domain.PreparationsCategory"/>
</set>
<many-to-one name="parentCategory"
class="org.binarus.domain.PreparationsCategory"
column="ParentID"
cascade="none" />
<set name="preparations"
inverse="true"
cascade="all"
order-by="Name ASC">
<key column="CategoryID"/>
<one-to-many class="org.binarus.domain.Preparation"/>
</set>
</class>

And here my class

public class PreparationsCategory {

private int id = -1;

private String name = "";

private String description = "";

private PreparationsCategory parentCategory;

private Set childCategories = new HashSet();

private Set preparations = new HashSet();

public int getId() {
return id;
}

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

/**
* @return Returns the name.
*/
public String getName() {
return name;
}
/**
* @param name The name to set.
*/
public void setName(String name) {
this.name = name;
}

public String getDescription() {
return description;
}

public void setDescription(String description) {
this.description = description;
}

public PreparationsCategory getParentCategory() {
return parentCategory;
}

public void setPerentCategory(PreparationsCategory parentCategory) {
this.parentCategory = parentCategory;
}

public Set getChildCategories() {
return childCategories;
}

public void setChildCategories(Set childCategories) {
this.childCategories = childCategories;
}

public void addChildCategory(PreparationsCategory category) {
if (category == null) {
throw new IllegalArgumentException("Null child category!");
}
if (category.getParentCategory() != null) {
category.getParentCategory().getChildCategories().remove(category);
}
childCategories.add(category);
category.setPerentCategory(this);
}

public void deleteChildCategory(PreparationsCategory category) {
if (category == null ) {
throw new IllegalArgumentException("Null child category!");
}
if (category.getParentCategory() != this) {
throw new IllegalArgumentException("Wrong child-parent relationship!");
}
childCategories.remove(category);
category.setPerentCategory(null);
}

public Set getPreparations() {
return preparations;
}

public void setPreparations(Set preparations) {
this.preparations = preparations;
}

public String toString() {
return name;
}


public void setParentCategory(PreparationsCategory parentCategory) {
this.parentCategory = parentCategory;
}
}

Code that I try to execute

StringBuilder query = new StringBuilder(
"SELECT {PreparationsCategories.*} FROM PreparationsCategories WHERE ");
query.append("ParentId=0");
query.append(" ORDER BY ID ASC, Name ASC");

categoriesList = session.createSQLQuery(query.toString(),
"PreparationsCategories", PreparationsCategory.class).list();

Tree has one root node with id=0 and ParentId=-1, all others nodes have ParentId 0 or another indeed exists node