JavaBean Example

[Willian Corcel]

Many people says that the Business Logic is inside JavaBeans...
Could anyone show me an example of Javabean that have business logic inside?

[Joe Pluta]

Well, there are all kinds of "business logic", from formatting to calculations to validation to persistence. Here's a very simple example, using formatting. The bean is called Name, and supports three attributes: first, last and middle. There are getters and setters for each attribute.
However, there is also one additional getter, getFull, which will return the formatted full name. For example, if the name attributes are "Joseph", "Dominic", and "Pluta", the getFull method will return the value "Joseph D. Pluta". This is the "business logic" for the Name method, and is encapsulated in the bean.

public class Name {
private String first;
private String last;
private String middle;
public Name() {
super();
}
public String getFirst() {
return first;
}
public String getLast() {
return last;
}
public String getMiddle() {
return middle;
}
public String getFull() {
StringBuffer sb = new StringBuffer();
sb.append(first);
sb.append(' ');
try
{
sb.append(middle.charAt(0));
sb.append(". ");
} catch(Exception e) {}
sb.append(last);
return last;
}
public void setFirst(String newFirst) {
first = newFirst;
}
public void setLast(String newLast) {
last = newLast;
}
public void setMiddle(String newMiddle) {
middle = newMiddle;
}
}

Joe

[Willian Corcel]

Actually I don't beliave it is a BUSINESS LOGIC.
What you put in the Javabean would be a "PRESENTATION LOGIC", isn't it?

[Joe Pluta]

Ugh. Okay, now you're to the point of making very fine distinctions. I probably shouldn't have used a formatting example. If you wanted something specific to business logic, you would have something like this:

public class Order {
  private Vector orderLines;
  (...)
  public BigDecimal getTaxableAmount()
  {
    BigDecimal taxableAmount = new BigDecimal(0.00);
    Enumeration e = orderLines.elements();
    while (e.hasMoreElements())
    {
      OrderLine l = (OrderLine) e.nextElement();
      if (l.getItem().isTaxable())
        taxableAmount = taxableAmount.add(l.getExtendedAmount());
    }
    return taxableAmount();
  }
}

The business rule in place here is that the order line is only taxable if the item is taxable. Thus, the total taxable amount only includes those order lines whose items are taxable. Now, in this particular case the ultimate decision as to whether something is taxable is in the Item class. However, in other businesses, other rules may apply. That's what makes generalizing business rules so difficult.
Joe