Play Framework - Pagination using JPA

Question

It seems to be the following syntax didn't work. Do we have any alternate query for this?

JPA.em().createQuery(queryStr).getResultList().from(startAt).fetch(offset);

As we know, from() and fetch() will work only on JPAQueryobject and the above code will produce List instead of JPAQueryobject.

Please note that queryStr combines 2 different models.

Is there anyway to get JPAQueryobject from the above query? So that I can use from and fetch.

Answer 1

Could you be a little more precise about the "didn't work" part? Do you have any error, or something like that?

On my application, I implemented some pagination features, and an example of the JPA query is this one ( News is one model of my application):

public static void news(int size, int page) {
    // 'size' is the number of elements displayed per page
    // 'page' is the current page index, starting from 1.
    int start = page * size;
    List<News> allNews = News.find("order by date desc").from(start).fetch(size);
    // Once the list of news is found, we return them in Json format...
    renderJSON(allNews, new NewsJsonSerializer());
}

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Regarding your edit: The method createQuery returns a Query object. Thus, you can use setFirstResult() method and setMaxResults() instead of from() and fetch() . Applied on your code, your query now looks like:

JPA.em().createQuery(queryStr).setFirstResult(startAt).setMaxResults(offset).getResultList();