Question

While retrieving a list of objects, I want to filter the results based on another table which I only have the ID of.The objects are NOT linked in the ORM-model, but instead just contain a UUID.

Ie:

@Entity
class A {
    @Id
    private UUID id;
    private UUID refB; // links to B
}

@Entity
class B {
    @Id
    private UUID id;
    private boolean visible;
}

I want to retrieve all A’s where B.hidden is false OR where B doesn’t exist.

In SQL I would do something like

SELECT t0.* FROM a_table t0 LEFT JOIN b_table t1 ON (t0.ref_b = t1.id)
    WHERE t1.hidden IS NULL OR t1.hidden = 0;

The reason I’m not just using RawSql is that I cannot find any way to use wildcards in the select, so all the attributes would have to be both maintained and manually added in the select.

I have also tried

List<A> listA = Ebean.find(A.class).where()
     .join("LEFT JOIN b_table t1 ON (t0.ref_b = t1.id)")
     .where().in("t1.hidden", "0", "NULL");

But then I get an error because WHERE is put before “LEFT JOIN”.

I assume that the “right” way would be to replace “private UUID refB” with “private B refB”. But doing that would make it easier to circumvent certain security measures.

Is this possible or will I have to add all attributes in a RawSql?

Answer 1

Filtering in Ebean is for other purposes than just manipulating the WHERE clause, look at the comparison in other question.

Here you have a proper way (I changed models to show complete, working sample)

Models

@Entity
public class A extends Model {

    @Id
    public Integer id;

    @ManyToOne
    public B b;

    public static Finder<Integer, A> find
                = new Finder<Integer, A>(Integer.class, A.class);

}

@Entity
public class B extends Model {

    @Id
    public Integer id;
    public Boolean hidden;

    public static Finder<Integer, B> find
            = new Finder<Integer, B>(Integer.class, B.class);

}

Controller

public static Result index() {

    // Insert some data one every request
    B bFalse = new B();
    bFalse.hidden = false;
    bFalse.save();

    B bTrue = new B();
    bTrue.hidden = true;
    bTrue.save();

    A a1 = new A();
    a1.b = bFalse;
    a1.save();

    A a2 = new A();
    a2.b = bTrue;
    a2.save();

    A a3 = new A();
    a3.b = bTrue;
    a3.save();

    // Let's search...
    List<A> aListOfNotHidden = A.find.where().and(Expr.eq("b.hidden", false), Expr.isNotNull("b.hidden")).findList();
    for (A a : aListOfNotHidden) {
        Logger.info("NOT hidden " + a.id);
    }

    List<A> aListOfHidden = A.find.where().eq("b.hidden", true).findList();
    for (A a : aListOfHidden) {
        Logger.warn("HIDDEN " + a.id);
    }

    return ok("check logs in your console");
}

Result SQLs of H2

-- all NOT hidden
select t0.id c0, t0.b_id c1
from a t0
left outer join b t1 on t1.id = t0.b_id
where (t1.hidden = false  and t1.hidden is not null ) 

-- all hiden
select t0.id c0, t0.b_id c1 
from a t0
left outer join b t1 on t1.id = t0.b_id  
where t1.hidden = true 

Alternatively you can also use SqlQuery to fetch just a SqlRows (not objects) check linked APIs for samples of usage, setting named parameters etc.:

List<SqlRow> rows = Ebean.createSqlQuery("select t0.*  " +
        "from a t0 left outer join b t1 on t1.id = t0.b_id " +
        "where (t1.hidden = false  and t1.hidden is not null ) ").findList();


for (SqlRow row : rows) {
    // do something with each row here, use methods such 
    // as getString("fieldname") for retrieving data  
    // (from SqlRow API)
}