Using generics with Morphia & MongoDB

Short Description:

I'm having trouble with reading a document from mongo DB into a java class with a generic property. The error says java.lang.Double cannot be cast to com.mongodb.DBObject

Long Description:

I have a java class / mongoDb-Collection called RandomDataCollection which has properties of type MyGenericProperty<T>

@Getter @Setter @NoArgsConstructor @Entity("randomDataCollection")
public class RandomDataCollection {

	@Id
    private ObjectId id = new ObjectId();

    private String name;

    @Embedded
    private MyGenericProperty<Float> temperatureMumbai;

}

MyGenericProperty<T> looks like this

@Getter @Setter @NoArgsConstructor
public class MyGenericProperty<T> {

	private T value;

	private String unit;

}

Writing to the DB works as expected...

MyGenericProperty<Float> temperatureMumbai = new MyGenericProperty<Float>();
temperatureMumbai.setValue(32.8f);
temperatureMumbai.setUnit("°C");

RandomDataCollection randomData = new RandomDataCollection();
randomData.setName("RandomData0711");
randomData.setTemperatureMumbai(temperatureMumbai);

Datastore datastore = getDatastore();
datastore.save(randomData);

...but when I try to read from the DB...

randomData = datastore.find(RandomDataCollection.class).filter("name =", "RandomData0711").get();

...I get the following exception:

Caused by: java.lang.ClassCastException: java.lang.Double cannot be cast to com.mongodb.DBObject

I did find some discussions about generics and morphia but to be honest I didn't know how to apply those to my issue.

I'm running Morphia 1.5.8

There is almost certainly a better way to do this but this worked for me.

DBCursor cursor = datastore.find(RandomDataCollection.class).filter("name =", name).fetch().getCursor();
List<RandomDataCollection> list = new ArrayList<>();
while (cursor.hasNext()) {
	DBObject theObj = cursor.next();
	RandomDataCollection rec = new RandomDataCollection();
	rec.setId((ObjectId)theObj.get("_id"));
    MyGenericProperty<Float> temperatureMumbai = new MyGenericProperty<Float>();
    BasicDBObject x = (BasicDBObject)theObj.get("temperatureMumbai");
    temperatureMumbai.setValue(x.getFloat("value"));
    temperatureMumbai.setUnit(x.getString("unit"));
    rec.setTemperatureMumbai(temperatureMumbai);
    list.add(rec);
}