Swing Hacks

Add Velocity for Dynamic HTML #98

Chapter 12, Miscellany

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497

HACK

Create a Velocity Context

Now, you need to make a VelocityContext to supply dynamic values to your

template. Create a method called

createContext and loop through the

weather collection, which contains three

Weather

objects:

private VelocityContext createContext(Collection weatherCollection) {

VelocityContext context = new VelocityContext( );

int index = 1;

for (Iterator iterator = weatherCollection.iterator( );

iterator.hasNext( );) {

Weather weather = (Weather) iterator.next( );

//add info to context

index++;

}

return context;

}

Next, create a variable for each day, since all of the VTL is keyed on a mea-

surement, as well as the day (

DAY1, DAY2, or DAY3):

String day = "DAY" + index;

Now, add the day itself, as well as entries for temperature, humidity, and

pressure:

context.put(day, weather.getDay( ));

context.put(day + "_TEMP", weather.getTemperature( ));

context.put(day + "_HUMIDITY", weather.getHumidity( ));

context.put(day + "_PRESSURE", weather.getPressure( ));

Fill the Template with Values

This is the easiest part. The code below is boilerplate code to initialize the

Velocity engine and run a template (

htmlText) through Velocity with a con-

text. It then returns the completed HTML as a

String:

private String processString(VelocityContext context, String htmlText)

throws Exception {

StringWriter writer = new StringWriter( );

Properties properties = new Properties( );

Velocity.init(properties);

Velocity.evaluate(context,

writer,

null,

htmlText);

return writer.getBuffer().toString( );

}