如何返回特定类型而不是列表 <Object[]> 在休眠标准中？

Question

I have two classes

@Entity
public class user implements Serializable{
...
private Set<article> uploaded = new HashSet<article>();
...
@OneToMany(mappedBy="uploader")
public Set<article> getUploaded() {
return uploaded;
}

@Entity
public class article  implements Serializable{
....
private user uploader;
....
@ManyToOne
public user getUploader() {
    return uploader;
}

So there also are two tables in the database: user and article. I try to get data using Criteria:

tx = session.beginTransaction();
Criteria cr = session.createCriteria(article.class);
...
List<article> list = cr.list();

But the returned list is not List<article> , it's a List<Object> contains ARTICLE and USER, and I don't know how to get the ARTICLE data from the list. if I set FetchType.Lazy, then the returned list will be List<article> without USER data, but I also need the USER data...

Answer 1

The Criteria Hibernate class list() method return a raw List. So if you try to cast it you get an unchecked warning.

But the returned list is not List, it's a List contains ARTICLE and USER

It doesn't contain both article and user, it contains only the type you passed when you create the criteria. In this case:

Criteria cr = session.createCriteria(article.class);

The list returned will contain article objects.

You can get a list of article in different ways:

The easiest one:

//Cast the raw list, but this will give you an unchecked warning
List<article> list = (List<article>) cr.list(); 

Or you can copy the values in another list:

List<Object> list = cr.list();
List<article> articles = new ArrayList<article>();

for(Object object : list) {
   if(object instanceof article) {
      articles.add((article) object);
   } 
}

Look at this post : What is the "proper" way to cast Hibernate Query.list() to List<Type>?

Anyway, class names must start with an uppercase character for java naming conventions. article -> Article, user -> User

Answer 2

Use Projection or ResultSetTransformer:

.setResultTransformer(Transformers.aliasToBean(article.class));

it's easy to google.