Advanced Features Made Easy - Stripes...and Java Web Development is Fun Again - page 177

StringBuilder result = new StringBuilder();
for (Contact contact : contacts) {
result.append(contact).append(',');
}
result.setLength(result.length() - 1);
String recpt = (previous == null ) ? "" : previous + ",";
return recpt + result.toString();
}
return previous;
}
This code looks fine, but it won't work! Well, not yet, anyway, and I'll
tell you why. To decide how to populate a form input field, Stripes uses
a population strategy, which is an extension represented by the Popula-
tionStrategy interface. Out of the box, Stripes uses the DefaultPopulation-
Strategy , which prefers values from request parameters to values from
action bean properties when populating a form input field. Consider
this scenario, in which the user does the following:
• Types Fred in the To field
• Selects Daniel Greene from the contact box
• Clicks the arrow button next to the To field
The request parameters will be as follows:
message.to=Fred
contacts=(ID of Daniel Greene)
In the addTo ( ) event handler, our clever code combines the two param-
eters to set the message.to action bean property to Fred, Daniel Greene .
But the message.to= request parameter is still “Fred,” and that's the
value used by Stripes to populate the To text field.
So, what's a developer to do? Stripes provides an alternate population
strategy, BeanFirstPopulationStrategy , which looks at the action bean prop-
erty before the request parameter. That's what we want. Since it is a
Stripes extension, we just have to create a class that extends BeanFirst-
PopulationStrategy and add it to our extension package, stripesbook.ext :
Download email_19/src/stripesbook/ext/MyPopulationStrategy.java
package stripesbook.ext;
public class MyPopulationStrategy extends BeanFirstPopulationStrategy{
}