calculate.java

// set input parameter
query.setParameter("x", 1.23d);
query.setParameter("y", 4.56d);

// call the stored procedure and get the result
query.execute();
Double sum = (Double) query.getOutputParameterValue("sum");

calculate.sql

CREATE OR REPLACE FUNCTION calculate(
    IN x double precision,
    IN y double precision,
    OUT sum double precision)
  RETURNS double precision AS
$BODY$
BEGIN
    sum = x + y;
END;
$BODY$
  LANGUAGE plpgsql

defineCalculate.java

// define the stored procedure
StoredProcedureQuery query = this.em.createStoredProcedureQuery("calculate");
query.registerStoredProcedureParameter("x", Double.class, ParameterMode.IN);
query.registerStoredProcedureParameter("y", Double.class, ParameterMode.IN);
query.registerStoredProcedureParameter("sum", Double.class, ParameterMode.OUT);

get_reviews.sql

CREATE OR REPLACE FUNCTION get_reviews(bookid bigint)
  RETURNS refcursor AS
$BODY$
    DECLARE
      reviews refcursor;           -- Declare cursor variables                         
    BEGIN
      OPEN reviews FOR SELECT id, comment, rating, version, book_id FROM review WHERE book_id = bookId;
      RETURN reviews;
    END;
  $BODY$
  LANGUAGE plpgsql

getReviews.java

StoredProcedureQuery query = this.em.createStoredProcedureQuery("get_books", Book.class);
query.registerStoredProcedureParameter(1, void.class, ParameterMode.REF_CURSOR);
query.execute();
List<Book> books = (List<Book>) query.getResultList();
for (Book b : books) {
// do something useful
}