(Lazy) LEFT OUTER JOIN using the Hibernate Criteria API

Question

I want to perform a LEFT OUTER JOIN between two tables using the Criteria API. All I could find in the Hibernate documentation is this method:

Criteria criteria = this.crudService
            .initializeCriteria(Applicant.class)
            .setFetchMode("products", FetchMode.JOIN)
            .createAlias("products", "product");

However, this either performs an inner join or a right outer join, because of the number of results it returns.

I also want my join to be Lazy. How can I do this?

Cheers!

UPDATE: It seems that using aliases makes the join INNER JOIN automatically. There is something in the "background story" I have not grasped yet. So, no alias today. This leaves me with the problem of applying restrictions to the two tables, because they both have a column (or property, if this is more appropriate) 'name'.

Hettiehetty

Accept the answer already. – Scouring

I want to know you reference of "createAlia() in Hibernate by default creates a INNER JOIN". I have searched API and cannot see it. Thanks. – Subarctic

Answer 1

Sdavids answer's API is deprecated now. Its updated version is

....createAlias("employee", "emp", JoinType.LEFT_OUTER_JOIN)

Roede

Thanks. It helps me to eliminate usage of deprecated API – Landeros

Answer 2

If you need to left join on the products table just do:

.....createAlias("products", "product", Criteria.LEFT_JOIN);

Lynnettelynnworth

Deprecated now, use Ankit's answer – Signesignet

Answer 3

A join is in the SQL request. It can't be lazy.

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With Hibernate, to retrieve lazily this data, just exclude it from the HQL request. Then, when you access the getters on your entity (if your Session is still open), it will be loaded automatically (you don't have to write that part of the request).

Leeuwarden

Sorry, I didn't get this. Perhaps I should rephrase: I want to have a LEFT OUTER JOIN, but also I want the data to be actually retrieved only when needed (the appropriate getter is called). Is Laziness (or eagerness) somehow connected with the type of SQL JOIN that takes place? – Hettiehetty

Lazyness may be realised with objects, but not with an SQL request. A request is executed once fully, it is not designed so that part of the request is executed later if needed! – Leeuwarden

In HQL I write LEFT OUTER JOIN FETCH. So, presumably an HQL query corresponds to many SQL ones, which are executed when needed? Anyway, lazily or not, how can I do a LEFT OUTER JOIN? And not in HQL, using the Criteria API. Cheers! – Hettiehetty

@Markos For joins, the HQL query get translated to only one equivalent SQL query. For the Criteria part, I'm not the expert... :-) – Leeuwarden