Question

I’m trying to construct a complex query. My entities look as follows:

@Entity
public class Configuration{

   @Id
   @Column(name="CONF_ID")
   protected Long configurationId;

   @ManyToMany
   @MapKey(name="componentType")
   @JoinTable(name="CONF_COMP",
      joinColumns={@JoinColumn(name="CONF_ID", referencedColumnName="CONF_ID")},
      inverseJoinColumns={@JoinColumn(name="COMP_ID", referencedColumnName="componentId")})
   protected Map<String, Component> components;
}

And

@Entity
public class Component {

    @Id
    protected long componentId; 
    @ElementCollection
    protected Map<String, String> properties;

    @ManyToMany(mappedBy="components")
    private List<Configuration> configurations;

    @Column(name="COMP_TYPE")
    protected String componentType;
 }

My problem lies in querying the properties field properly. I can’t seem to create a query to get all Configurations where Component A has Property Prop1 = 1 and Component B has Property Prop2=2.
I tried the following without success.

Root<Configuration> conf = cq.from(Configuration.class);    
MapJoin<Configuration, String, Component> compJoin = conf.join(Configuration_.components, JoinType.LEFT);
MapJoin<Component, String, String> propJoin = compJoin.join(Component_.properties, JoinType.LEFT); 

    Predicate p1 = cb.and(
                cb.equal(mapJoin.key(), "A"),
                cb.equal(propJoin.key(), "Prop1"), cb.equal(propJoin.value(), "1"));
    Predicate p2 = cb.and(
                cb.equal(mapJoin.key(), "B"),
                cb.equal(propJoin.key(), "Prop2"), cb.equal(propJoin.value(), "2"));

Predicate[] pArray = new Predicate[]{p1, p2};
cq.where(pArray);
cq.select(conf).distinct(true);

EDIT: The query, as outputted by the logger, looks like this:

SELECT DISTINCT  t2.CONF_ID, t2.DTYPE, t2.TOTALPRICE, t2.NAME
 FROM CONFIGURATION t2 
 LEFT OUTER JOIN (CONF_COMP t3 JOIN COMPONENT t1 ON (t1.COMPONENTID = t3.COMP_ID)) ON (t3.CONF_ID = t2.CONF_ID) LEFT OUTER JOIN Component_PROPERTIES t0 ON (t0.Component_COMPONENTID = t1.COMPONENTID) 
WHERE (((((t1.COMP_TYPE = ?) AND (t0.PROPERTIES_KEY = ?)) AND t0.PROPERTIES LIKE ?) AND (((t1.COMP_TYPE = ?) AND (t0.PROPERTIES_KEY = ?)) AND t0.PROPERTIES LIKE ?)) AND (t2.DTYPE = ?))
bind => [7 parameters bound]

I’m guessing it is trying to find a Configuration where all the conditions apply to the SAME component maybe? It works if I apply restrictions on only one Component, but I get an empty result list when applying 2 or more, although there are entries in the DB that satisfy the conditions.

UPDATE

After following Pimgd’s suggestion, i ended up with a query that looks like this:

SELECT DISTINCT t1.CONF_ID, t1.DTYPE, t1.TOTALPRICE, t1.NAME
FROM CONFIGURATION t1 LEFT OUTER JOIN (CONF_COMP t2 JOIN COMPONENT t0 ON (t0.COMPONENTID = t2.COMP_ID)) ON (t2.CONF_ID = t1.CONF_ID) 
WHERE ((( 
    t0.COMPONENTID IN (SELECT t3.COMPONENTID 
                        FROM COMPONENT t3 LEFT OUTER JOIN Component_PROPERTIES t4 ON (t4.Component_COMPONENTID = t3.COMPONENTID) 
                        WHERE ((t4.PROPERTIES_KEY = Brand) AND (t4.PROPERTIES = Intel)))) 

    AND 
    t0.COMPONENTID IN (SELECT t6.COMPONENTID 
                        FROM COMPONENT t6 LEFT OUTER JOIN Component_PROPERTIES t7 ON (t7.Component_COMPONENTID = t6.COMPONENTID) 
                        WHERE ((t7.PROPERTIES_KEY = Capacity) AND t7.PROPERTIES LIKE 4GB%))))

One criteria works, two yield no results.

Any help much appreciated!

Answer 1

I’m gonna say that
mapJoin.key() should be compJoin.key().

Other than that, I don’t see anything wrong.

If my offered solution doesn’t work, here are some bonus questions for you:

• What are the results you are getting?
• Is it possible to show the generated queries?

An interesting bit I spotted:
WHERE (((((t1.COMP_TYPE = ?) AND (t0.PROPERTIES_KEY = ?)) AND t0.PROPERTIES LIKE ?) AND (((t1.COMP_TYPE = ?) AND (t0.PROPERTIES_KEY = ?)) AND t0.PROPERTIES LIKE ?)) AND (t2.DTYPE = ?))


What if, I take this bit out… just for clarification. ((t1.COMP_TYPE = ?) AND (t0.PROPERTIES_KEY = ?))

WHERE (((SNIP AND t0.PROPERTIES LIKE ?) AND (SNIP AND t0.PROPERTIES LIKE ?)) AND (t2.DTYPE = ?))

So yeah…
Now how would you go about fixing your query?
Sadly, I am no expert.
But what I do know is that if you made a query with a where going WHERE t2.CONF_ID IN (Subselect for criteria A) AND t2.CONF_ID IN (Subselect for criteria B).

My suggestion would be to look up subselects and abuse those. JPA 2.0, Criteria API, Subqueries, In Expressions explains it and seems relevant enough.