Making join with Criteria

Question

I'm terribly new to Hibernate. I've googled for two hours but I still can't figure out, how to make JOIN without using HQL, only by criteria. I have tables Clients(cID, name) and Visits(vID, vcID, date). The relation is one to many (one client can visit multiple times). I would also like to do it without setFetchMode. Just Criteria. Do I have to change the mappping xml?

UPDATE: this is part of my mapping xml:

 <class name="Client" table="Clients"> <id name="cID" column="cID"><generator class="native"/></id> <property name="name" length="10" not-null="true"/> </class> <class name="Visit" table="Visits"> <id name="vID" column="vID"><generator class="native"/></id> <property name="vcID" length="10" not-null="true"/> <property name="date" length="25" not-null="true"/> </class>

can you post here what is your current mapping and how you're trying to make the query? not enough information. — Eugene Retunsky
– Eugene Retunsky, Commented Apr 9, 2012 at 18:41

PepperBob · Accepted Answer · 2012-04-09 19:45:49Z

Having a class Client with a list-attribute "visits" that's mapping to your Visit-Entity:

Criteria criteria = session.createCriteria(Client.class); criteria.addCriteria("visits");

This would create an inner join between your client-table and your visits-table.

Update:

Here you'll find some good examples: http://docs.jboss.org/hibernate/orm/3.3/reference/en/html/querycriteria.html#querycriteria-associations

Mapping Example

I hardly ever use hibernate mapping xml, however it should read similiar to:

 <class name="Client" table="Clients"> <id name="cID" column="cID"><generator class="native"/></id> <property name="name" length="10" not-null="true"/> <bag name="visits"> <key column="vcId"/> <one-to-many class="Visit"/> </bag> </class>

Tell Hibernate that there is a property "visits" which represents a one-to-many relationship.

But how to resolve this without special list-attribute "visits"? I'm looking for equivalent for "SELECT name FROM Clients JOIN Visits ON vcID = cID". In the first post I put my mapping xml. Should I change something there?
Yes, your Client class needs a collection mapping to your Visits class, esp. defining the 1-n relation, see link
So if I implemented such list(private List visits = new ArrayList();), what should I add to mapping xml? That document is not very clear for me.

Eugene Retunsky · Accepted Answer · 2012-04-09 20:26:51Z

You need to update you mapping:

 <class name="Client" table="Clients"> <id name="cID" column="cID"><generator class="native"/></id> <property name="name" length="10" not-null="true"/> <!-- Declare Set<Visit> visits in the Client class--> <set name="visits" lazy="false" cascade="all"> <key column="vcID"/> <one-to-many class="your.package.Visit"/> </set> </class> <class name="Visit" table="Visits"> <id name="vID" column="vID"><generator class="native"/></id> <!-- and add "Client client" property to your Visit class --> <many-to-one name="client" column="vcID" lazy="false"/> <property name="date" length="25" not-null="true"/> </class>

Then:

 Criteria criteria = session.createCriteria(Visit.class).addCriteria("client") .add(Restriction.eq(...));

or

Criteria criteria = session.createCriteria(Client.class).addCriteria("visits") .add(Restriction.eq(...));

And Hibernate will join them automatically.

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