Question

I have a Recipe entity that contains two images:

@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable="true")
public class Recipe {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    private Key key;
    @Persistent
    private MyImage myImage; // full-size image
    @Persistent
    private MyImage thumb; // 224x230 thumbnail version of the above

    public Recipe(Key userKey, String title, Text content, MyImage myImage, MyImage thumb, Set<String> tags) {
        this.userKey = userKey;
        this.title = title;
        this.content = content;
        this.myImage = myImage;
        this.thumb = thumb;
        this.tags = tags;
    }
    public MyImage getMyImage() {
        return myImage;
    }
    public void setMyImage(MyImage myImage) {
        this.myImage = myImage;
    }
    public MyImage getThumb() {
        return thumb;
    }
    public void setThumb(MyImage thumb) {
        this.thumb = thumb;
    }
}

When I persist this to the datastore, the images are stored correctly.
However the issue comes when I try referencing the images using
.getMyImage() and .getThumb().
They both point to the same object even though I can see in the
datastore viewer that they are two images of different size. If they
are stored in the datastore corretly this means that there’s an issue
with how I reference the object I suppose. Why is this?

This is the object I persist, and as you can see the myImage and
thumb objects are different (not showing the code for them, but
trust me they are).

Recipe recipe = new Recipe(user.getKey(), title, new Text(content), myImage, thumb, tagsAsStrings);

Any ideas why I keep on referencing the same object?

Answer 1

I realized that my logs were showing “This is not yet supported.”. It’s a pity that this feature is not supported, however I had a simple workaround.

Instead of:

@Persistent
private MyImage myImage; // full-size image
@Persistent
private MyImage thumb; // 224x230 thumbnail version of the above

I put:

private List<MyImage> images; // contains 2 elements
                              // index 0 full-size, 1 is thumbnail (224x230);
                              // since JDO app-engine doesn't support
                              // 2 attributes of the same type

So basically a list of two images instead of two distinct images. This works!