I get a ClassCastException

[Songezo Nkukwana]

Learning how to use Hibernate Criteria, i get the following error

java.lang.ClassCastException : [Ljava.lang.Object;

here ->

 List ranks = getSession().createCriteria(Rank.class)
		.setProjection( Projections.projectionList()
			.add( Projections.property("rankId"))
			.add( Projections.property("description"))
			.add( Projections.property("auditInfo.chgId"))
			.add( Projections.property("auditInfo.crtId"))
			.add( Projections.property("auditInfo.chgDat"))
			.add( Projections.property("auditInfo.crtDat"))		
			.add( Projections.property("rankProfiles"))
	).list();
				
Iterator it = ranks.iterator();

while (it.hasNext()) {
	Rank rnk = (Rank) it.next();
	log4j.info("ID: " + rnk.getRankId() + " - DESCRIPTION - " + rnk.getDescription()); 
}

Pojo ->

/** POJO object */
public class Rank {

	private String rankId;
	private String description;
	private Auditable auditInfo;
	private Set rankProfiles = new HashSet(0);

	// Constructors

	public Rank() {
	}
	
	// Property accessors

	public String getRankId() {
		return this.rankId;
	}

	public void setRankId(String rankId) {
		this.rankId = rankId;
	}

	public String getDescription() {
		return this.description;
	}

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

	public Auditable getAuditInfo() {
		return auditInfo;
	}

	public void setAuditInfo(Auditable auditInfo) {
		this.auditInfo = auditInfo;
	}

	public Set getRankProfiles() {
		return this.rankProfiles;
	}

	public void setRankProfiles(Set rankProfiles) {
		this.rankProfiles = rankProfiles;
	}
}

Probably complaining about casting Object to TestRank? but this works

List ranks = getSession().createCriteria(Rank.class).list();

Iterator it = ranks.iterator();

while (it.hasNext()) {
	Rank rnk = (Rank) it.next();
	log4j.info("ID: " + rnk.getRankId() + " - DESCRIPTION - " + rnk.getDescription()); 

???

[Paul Sturrock]

If you use Projections this way your result will be a List of arrays of Objects, not a List of POJOs. Given you have all the properties you are Projecting already in your POJO I don't see what benefit using Projections is giving you here. What is it you are trying to achieve?

[Songezo Nkukwana]

Paul Sturrock wrote:If you use Projections this way your result will be a List of arrays of Objects, not a List of POJOs. Given you have all the properties you are Projecting already in your POJO I don't see what benefit using Projections is giving you here. What is it you are trying to achieve?

If you don;t mind could you please explain the use of projections.property? I'm new to hibernate and busy using examples but some are not clear enough ... Thanks Paul

[Paul Sturrock]

You might use Projections to query for properties not on the object you are querying, for example a derived property (thing average, maximum etc.) Or you might use them to create a new, unmapped object at runtime. If all you are doing is returning the properties of an already mapped object then you don't need to use them.

[Songezo Nkukwana]

Paul Sturrock wrote:You might use Projections to query for properties not on the object you are querying, for example a derived property (thing average, maximum etc.) Or you might use them to create a new, unmapped object at runtime. If all you are doing is returning the properties of an already mapped object then you don't need to use them.

How should i interpret the following 'incomplete' queries?

// 1.
session.createCriteria(Father.class).createCriteria("son")...;
//2.
session.createCriteria(Father.class).createAlias("son")...;
// 3.
session.createCriteria(Father.class).setFetchMode("son")...;

Perhaps am trying to figure which should i use for one to many relationship?

[Songezo Nkukwana]

In fact Paul, looking at the POJO i posted, how would i write a Criteria query to get all RankProfiles with a specified id? Note that RankProfile has a many to one Rank relationship, so a Rank can be associated with many RankProfiles ... I think given such examples, i may be set to begin coding my Criterion queries

[Paul Sturrock]

What you might do is add another criterion on rankProfiles that matches on id. Have a look at this for an example.

[Songezo Nkukwana]

I tried these two methods

List ranks = getSession().createCriteria(Rank.class)
	.setFetchMode("RankProfile", FetchMode.JOIN)					
	.add(Restrictions.eq("rankId", "01"))
	.list();

List ranks = getSession().createCriteria(Rank.class)
	.add( Restrictions.like("rankId", "01") )
	.createCriteria("rankProfiles")
	.add( Restrictions.like("rank.rankId", "01") )
	.list();

Both seem to work, which one is recommended? Would they work for lazy-initialization/loading?