Spring with Hibernate, join data from another table and map to a new helper object

first i have to say i am quite new with spring and hibernate.

now my situation: i have one table named Places which has: Id PK, name and description. i have a second table named Edges which has: ID PK, fromPlaces (fk to the pk id from places), and toPlaces (also referenced to the id from places).

now i want to make a query which will eventually map to an object which will have my Edge object plus both the names of the fromPlace reference and toPlaces reference.

currently i have this in my DAO which is functioning properly:

public List<Edge> listEdges() {
    return sessionFactory.getCurrentSession().createQuery("from Edge")
            .list();
}

Please any good tutorial or any code examples you can give me to help me with the process of building what i need. i dont know if its helpful but i am using annotations to wire everything.

SECOND EDIT: ADding the solution to my classes for both referencing and afterwards if a Place is removed to automatically remove the references to Edge objects.

   @Entity
@Table(name="PLACES")
public class Place {

        @Id
        @Column(name="ID")
        @GeneratedValue
        private Integer id;

        @Column(name="NAME")
        private String name;

        @Column(name="DESCRIPTION")
        private String description;

        @Column(name="IMAGEURL")
        private String imageUrl;

        @Column(name="ISVALIDDESTINATION")
        @Type(type = "org.hibernate.type.NumericBooleanType")
        private boolean validDestination;

        @OneToMany(cascade = CascadeType.ALL)
        @JoinColumn(name = "FROMPLACE_ID")
        private Set<Edge> fromPlace = new HashSet<Edge>(0);

        @OneToMany(cascade = CascadeType.ALL)
        @JoinColumn(name = "TOPLACE_ID")
        private Set<Edge开发者_StackOverflow社区> toPlace = new HashSet<Edge>(0);

And this is my edge model: note i am ommiting the getters and setters here because they have no annotations,they are just standard.

   @Entity
    @Table(name = "EDGES")
    public class Edge {

        @Id
        @Column(name = "ID")
        @GeneratedValue
        private Integer id;

        @ManyToOne(fetch=FetchType.EAGER)
        @JoinColumn(name="FROMPLACE_ID")
    private Place fromPlace;

    @ManyToOne(fetch=FetchType.EAGER)
        @JoinColumn(name="TOPLACE_ID")
    private Place toPlace;

        @Column(name="COST")
        private Integer cost;

First of, you need to map your entities. "Hibernate Annotations" docs are a good place to start.

Links from Edge to Places (BTW, naming your entities in plural is confusing; I think that's why duffymo suggested collections) should be mapped as @ManyToOne

Once you do that, your listEdges method above would return a list of Edge objects, each of which would have (possibly lazily populated) getFromPlaces() and getToPlaces() methods returning appropriate Places instances.

Now, if you want to return a separate helper object that contains Edge and only names of relevant Places entities, you'll have to create that object along with appropriate constructor and write a query referencing that constructor.

This is a bit more advanced, though - I'd recommend you get the first part working and look into working with lazy associations before you proceed with this.

Edit (based on question update):

Your Edge mapping should instead be something like:

@Entity
@Table(name = "EDGES")
public class Edge {

    @Id
    @GeneratedValue
    private Integer id;

    @ManyToOne
    @JoinColumn(name="FROMPLACE")
    private Place fromPlace;

    @ManyToOne
    @JoinColumn(name="TOPLACE")
    private Place toPlace;
}

Note that it's not necessary to specify @Column on fields whose name matches column name. Also note that it's common to use "_ID" suffix to indicate foreign keys (e.g. "FROMPLACE_ID") - if you do that, you can omit @JoinColumn declarations as well.

Stop thinking less in terms of tables and more in terms of objects.

You need an Edge object with 1:m relationships to Place references, to and from.