SimpleJdbcCall f = new SimpleJdbcCall(jdbcTemplate)
                .withSchemaName("MY_SCHEMA")
                .withCatalogName("MY_PACKAGE")
                .withFunctionName("MY_FUNCTION");
SqlParameterSource in = new MapSqlParameterSource().addValue("p_in_param", intVar);

function MY_FUNCTION (p_in_param in number) return number;

int pNum = f.executeFunction(Integer.class, in).intValue();

java.lang.ClassCastException: java.math.BigDecimal cannot be cast to java.lang.Integer

int pNum = ((java.math.BigDecimal)f.executeFunction(Integer.class, in)).intValue();

Object obj = f.executeFunction(Integer.class, in);
pNum = ((java.math.BigDecimal)obj).intValue();