How to call a custom Oracle function returning a value from JPA

Question

I have a custom function in oracle returning a number after deleting records. I could get a value in sql_plus such as

call my_function(4) into :out_number;
<         


        

Answer 1

From https://vladmihalcea.com/how-to-call-oracle-stored-procedures-and-functions-from-hibernate/:

First, we can simply call the Oracle function just like any other SQL query:

BigDecimal commentCount = (BigDecimal) entityManager
    .createNativeQuery(
        "SELECT fn_count_comments(:postId) FROM DUAL"
    )
    .setParameter("postId", 1L)
    .getSingleResult();

Another approach is to call the database function using plain JDBC API:

Session session = entityManager.unwrap( Session.class );

final AtomicReference commentCount = 
    new AtomicReference<>();

session.doWork( connection -> {
    try (CallableStatement function = connection
            .prepareCall(
                "{ ? = call fn_count_comments(?) }"
            )
        ) {
        function.registerOutParameter( 1, Types.INTEGER );
        function.setInt( 2, 1 );
        function.execute();
        commentCount.set( function.getInt( 1 ) );
    }
} );