There’s More to Life Than Strings: Working with Data Types - Stripes...and Java Web Development is Fun Again - page 95

Stripes offers solid built-in type conversion support. Let's discuss how
to convert data types to String s: formatting.

5.3 Formatting

Formatting is type conversion in the opposite direction. An object of
type T must be converted to a String to be displayed to the user. There's
always the toString ( ) method, but Stripes gives us a more powerful way.
With formatters, the value can easily be displayed in different ways and
can do so in a locale-sensitive manner as well.

As shown in Figure 5.3 , on the following page, a formatter is an imple-
mentation of the Formatter<T> interface and returns a String for a given
object of type T . Formatters are called upon when we use Stripes tags
that support formatted values, such as <s:format> and <s:text>. When
the tag refers to a property of type T , Stripes uses a Formatter<T> imple-
mentation to convert the property's value to a String , which is returned
to the tag.

Here is the Formatter<T> interface:

public interface Formatter<T> {
void setLocale(Locale locale);
void setFormatType(String formatType);
void setFormatPattern(String formatPattern);
void init();
String format(T input);

}

Along with the user's locale, a formatter is given a type and a pat-
tern with the formatType= and formatPattern= attributes of format-aware
Stripes tags. The type indicates what to display, as in "date" , "time" , and
"datetime" for the Stripes Date formatter. The pattern describes how to
display the value, such as "short" , "medium" , "long" , and "full" .

Let's look at the formatters provided by Stripes.

Built-in Formatters
Stripes comes with built-in formatters for Date s, all Number types, and
enumerated types. The date and number formatters support differ-
ent format types, named patterns, and arbitrary patterns using the
Java SimpleDateFormat and DecimalFormat syntax. The result is format-
ted according to the user's locale.