Morphia: inheritance not handled properly?

Question

I have a class that implements an interface. Why are the arraylist contents not stored in the database? Here is some code to illustrate the problem.

The class

@Entity
public class MyClass implements MyInterface {

@Id
@Indexed
public String id;

public String someField;

public MyClass(String id, String someField){
    this.id = id;
    this.someField = someField;
}
}

The interface

public interface MyInterface {

@Embedded
public List<String> mylist = new ArrayList<String>();
}

Test code

@Test
public void test() {
    testInheritance();
}

public void testInheritance() {
    MyClass myClass = new MyClass("test", "someField");
    myClass.myList.add("wow");
    MyClassDao dao = new MyClassDao();
    dao.save(myClass);
}

public class MyClassDao extends BasicDAO<MyClass, ObjectId> {

    public MyClassDao() {
        super(MyClass.class, MorphiaManager.getMongoClient(), MorphiaManager.getMorphia(), MorphiaManager.getDB().getName());
    }
}

Result in DB

{
"_id" : "test",
"className" : "gr.iti.mklab.simmo.util.MyClass",
"someField" : "someField"
}

Answer 1

Interfaces can only declare method signatures and constants (static final variables). What you want to use is an abstract base class from which you inherit.

Additional observations from your code:

• The id should be ob the type ObjectId and is automatically indexed, you don't need the @Indexed
• Attributes should be private or protected and you need to provide getters and setters for them
• You need a default no-arg constructor in your entity class