How to Implement JOIN Clauses Using JPA Criteria API?

How can I dynamically add JOIN clauses when using the JPA Criteria API?

Class baseClass; 
CriteriaBuilder cb = JpaHandle.get().getCriteriaBuilder();
CriteriaQuery cq = cb.createQuery(this.baseClass);
Root entity_ = cq.from(this.baseClass);

The JPA Criteria API provides a type-safe way of constructing complex queries, including JOIN clauses. This allows you to create queries dynamically based on the structure of your entity classes.

CriteriaBuilder cb = JpaHandle.get().getCriteriaBuilder();
CriteriaQuery<Experiment> cq = cb.createQuery(Experiment.class);
Root<Experiment> experimentRoot = cq.from(Experiment.class);
Join<Experiment, Assay> assayJoin = experimentRoot.join("assay");
cq.select(experimentRoot).where(cb.equal(assayJoin.get("id"), someId));
Query query = JpaHandle.get().createQuery(cq);

Causes

• Lack of understanding of the Criteria API's structure.
• Not utilizing type-safe join methods provided by JPA.

Solutions

• Use the `join` method on the `Root` or `Join` object to create JOIN clauses.
• Utilize `CriteriaBuilder` for constructing predicates and utilizing fetches for eager loading.

Mistake: Attempting to use `join` incorrectly by referencing a column name instead of the relationship defined by annotations.

Solution: Always use the relationship name defined in entity annotations, such as `entity.join("assay")`, not the column name.

Mistake: Forgetting to set the selection of the query after adding JOIN clauses.

Solution: Always follow your join operations with a selection statement to specify the result set.