Question

I have a persistent object (Action) and auto generated data model (Action_). By having an object of Action class and an instance of SingularAttribute, is it possible to get the field corresponding to the given SingularAttribute?

I need a function like this:

public S getValue(T object,SingularAttribute<T,S> attribute);

My entity class (Action.java):

@Entity
@Table(name="ACTION")
public class Action implements Serializable {
    private long id;
    private String name;

    public Action() {
    }


    @Id
    @Column(unique=true, nullable=false, precision=6)
    public long getId() {
        return this.id;
    }

    public void setId(long id) {
        this.id = id;
    }


    @Column(length=50)
    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

My meta model class (Action_.java):

@StaticMetamodel(Action.class)
public class Action_ {
    public static volatile SingularAttribute<Action, Long> id;
    public static volatile SingularAttribute<Action, String> name;
}

Answer 1

You could use the getJavaMember() method to get the member, then test if this member is a Field or a Method, and access the field or call the method on the object using reflection.

You will probably have to make the field or method accessible before accessing/invoking it. And you will also have to handle primitive type conversion to objects.

The main question is: why do you need this?

If you need it only for this specific entity class, you could simply use a switch on the attribute name and return the appropriate value:

switch (attribute.getName()) {

    case "name":
        return action.getName();
    ...
}