calculate.java

@NamedStoredProcedureQuery(
	name = "calculate", 
	procedureName = "calculate", 
	parameters = { 
		@StoredProcedureParameter(mode = ParameterMode.IN, type = Double.class, name = "x"), 
		@StoredProcedureParameter(mode = ParameterMode.IN, type = Double.class, name = "y"), 
		@StoredProcedureParameter(mode = ParameterMode.OUT, type = Double.class, name = "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

callCalculate.java

StoredProcedureQuery query = this.em.createNamedStoredProcedureQuery("calculate");
query.setParameter("x", 1.23d);
query.setParameter("y", 4.56d);
query.execute();
Double sum = (Double) query.getOutputParameterValue("sum");

callGetBooks.java

List<Book> books = (List<Book>) this.em.createNamedStoredProcedureQuery("getBooks").getResultList();

callGetReviews.java

List<Book> books = (List<Book>) this.em.createNamedStoredProcedureQuery("getBooks").getResultList();
for (Book b : books) {
	StoredProcedureQuery q = this.em.createNamedStoredProcedureQuery("getReviews");
	q.setParameter(2, b.getId());
	List<Review> reviews = q.getResultList();
	for (Review r : reviews) {
		// do something
	}
}

get_books.sql

CREATE OR REPLACE FUNCTION get_books()
  RETURNS refcursor AS
$BODY$
    DECLARE
      books refcursor;           -- Declare cursor variables
    BEGIN
      OPEN books FOR SELECT id, publishingdate, title, version, publisher_id FROM book;   -- Open a cursor
      RETURN books;                                                       -- Return the cursor to the caller
    END;
  $BODY$
  LANGUAGE plpgsql

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

getBooks.java

@NamedStoredProcedureQuery(
	name = "getBooks", 
	procedureName = "get_books", 
	resultClasses = Book.class, 
	parameters = @StoredProcedureParameter(mode = ParameterMode.REF_CURSOR, type = void.class) 
)

getReviews.java

@NamedStoredProcedureQuery(
	name = "getReviews", 
	procedureName = "get_reviews", 
	resultClasses = Review.class, 
	parameters = {
		@StoredProcedureParameter(mode = ParameterMode.REF_CURSOR, type = void.class), 
		@StoredProcedureParameter(mode = ParameterMode.IN, type = Long.class)
	}
)