A presentation by Julz Cutaran, Exist Software Engineer, for the meetup of the Association of Filipino Java Developers or PinoyJUG at the TechBar in Ortigas on 03 Nov. 2010.

1. Common Pitfalls

2. 1. Not specifying columns in your select statement
(select *)

3. .
.
StringBuffer queryString = new StringBuffer();
queryString.append("SELECT DISTINCT o.name, o.code, o.price, d.discount “);
queryString.append("FROM com.exist.model.Order as o, “);
queryString.append("com.exist.model.Discounts as d “);
.
.
.
Session session = sessionFactory.getCurrentSession();
Query selectQuery = session.createQuery(queryString.toString());
List<Order> orders= selectQuery.list();
.
.
.
List<OrderTo> orderTo = new ArrayList<OrderTo>();
...
for(Order order:orders){
OrderTo oto = new OrderTo
oto.setName(order.getName());
.
.
.
orderTo.add(oto);
}
.
.
.
2. Select and Transfer

4. .
.
.
StringBuffer queryString = new StringBuffer();
queryString.append("SELECT DISTINCT new com.exist.to.OrdersTO ");
queryString.append("(o.name, o.code, o.price, d.discount) ");
queryString.append("FROM com.exist.model.Orders as o, ");
queryString.append("com.exist.model.Discounts as d “);
.
.
.
Session session = sessionFactory.getCurrentSession();
Query selectQuery = session.createQuery(queryString.toString());
.
.
.
List<OrdersTO> data = selectQuery.list();

5. 3. Not delegating computations
.
.
.
double bills = someService.getBills(referenceNo);
double payments = someService.getPayments(referenceNo)
double due = bills - payments;
.
.
.

6. public class Computations {
private SomeService someService;
private double bills;
private double payments;
private double due;
public Computations(SomeService someService, String reference) {
bills = someService.getBills(referenceNo);
payments = someService.getPayments(referenceNo)
due = bills - payments;
}
... <getters of bills, payments and due>
}

7. .
.
.
Computations computations = new Computations(someService, referenceNo);
double bills = computations.getBills();
double payments = computations.getPayments();
double due = computations.getDue();
.
.
.

8. 4. equals String literal
variable.equals(“String Literal”);

9. “String literal”.equals(variable);

10. 5. Computing using double or
Double
double minuend = 1.1d;
double subtrahend = 1.0d;
double difference = minuend – subtrahend;
Or
Double minuend = 1.1d;
Double subtrahend = 1.0d;
Double difference = minuend.doubleValue() – subtrahend.doubleValue();

11. BigDecimal minuend = new BigDecimal(1.1).setScale(2, RoundingMode.HALF_EVEN);
BigDecimal subtrahend = 1.0d;
BigDecimal difference = minuend.subtract(subtrahend);

12. 6. using objects in if
If (object.getBooleanProperty()) {
...
}

13. if (object!=null && object.getBooleanProperty()) {
...
}
Or
if (object!=null && object.getNumericProperty()>0) {
...
}

14. Thanks!