Best way to create JPA query that might contain a parameter or might not

Question

there\'s method that creates JPA query like this

        String queryString = \"SELECT i FROM Item i\";

        if (null != search) {
            queryStrin         


        

Answer 1

If you don't have to write the query in such a way that you're writing a query string, you could use the JPA Criteria API. You can see the class I call "ExampleDao" which I use for research and examples here.

You would then add an optional where clause to it, see example below:

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery criteria = cb.createQuery(Item.class);
Root root = criteria.from(Item.class);
criteria.select(root);

if (null != search) {
    String pattern = "%pattern here%";
    criteria.where(cb.like(root.get("name"), pattern));
}