Swing Hacks

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HACK

When you run Velocity with this context and this template, it will print out:

Jonathan is a total Rockstar

Create the HTML

You’ll probably want to create your pages in an HTML editor like Dream-

weaver. Better yet, have your graphics designers handle design, and then you

can add VTL tags to the HTML they create.

For each of the three days in the display, you need temperature, humidity,

pressure, and the name of the day. For each measurement, you need a vari-

able in VTL—call these

TEMP

,

HUMIDITY

, and

PRESSURE

—and preface them

with

DAY and the day number (like DAY1). Figure 12-14 is a screenshot from

Dreamweaver, where I built the page with all of the VTL. The dynamic data

for the day, temperature, humidity, and pressure are provided by VTL tags:

the first day’s name is

${DAY1}, its temperature is ${DAY1_TEMP}, etc.

Create a Data Object

Now, it’s time to leave template land and get into some Java code. You need

to write a data object to represent the weather for a particular day. You’ll

find this useful when you build up your context. To keep things simple,

Example 12-20 uses an immutable object.

Figure 12-14. Weather web page in Dreamweaver

Example 12-20. A simple weather data object

public class Weather {

private BigDecimal temperature;

private BigDecimal humidity;

private BigDecimal pressure;

private String day;

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Of course, you need to display all of this visual wizardry, so create a class

that contains a

JEditorPane for displaying the HTML. You can use which-

ever HTML renderer you choose, but

JEditorPane is a good choice because

it’s built into Swing. Example 12-21 is a basic container that contains a

JEditorPane and configures it to render HTML.

public Weather(BigDecimal temperature, BigDecimal humidity, BigDecimal

pressure, String day) {

this.temperature = temperature;

this.humidity = humidity;

this.pressure = pressure;

this.day = day;

}

public BigDecimal getTemperature( ) {

return temperature;

}

public BigDecimal getHumidity( ) {

return humidity;

}

public BigDecimal getPressure( ) {

return pressure;

}

public String getDay( ) {

return day;

}

}

Example 12-21. Panel to contain the HTML display pane

public class WeatherPanel {

private JEditorPane htmlPane;

public WeatherPanel( ) {

htmlPane = createHtmlPanel( );

}

private JEditorPane createHtmlPanel( ) {

JEditorPane editorPane = new JEditorPane( );

HTMLEditorKit editorKit = new HTMLEditorKit( );

editorKit.install(editorPane);

editorPane.setEditorKit(editorKit);

editorPane.setEditable(false);

return editorPane;

}

Example 12-20. A simple weather data object (continued)

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Chapter 12, Miscellany

#98 Add Velocity for Dynamic HTML

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Next, you need to add a method to reconfigure the htmlPane with a collec-

tion of

Weather objects:

public void displayWeather(String html, Collection weather){

String result = html;

try {

VelocityContext context = createContext(weather);

result = processString(context, html);

} catch (Exception e){

e.printStackTrace( );

}

htmlPane.setText(result);

}

You need to read in the HTML file you created, and that’s where

displayWeatherByFile( ) comes in. You supply it the filename, and it reads

the HTML in that file:

public void displayWeatherByFile(String fileName, Collection weather){

displayWeather(readFile(fileName), weather);

}

private String readFile(String fileName) {

StringBuffer htmlBuffer = new StringBuffer( );

try {

InputStream inputStream = WeatherPanel.class.

getResourceAsStream(fileName);

BufferedReader reader =

new BufferedReader(new InputStreamReader(inputStream));

while (true){

String line = reader.readLine( );

if (line != null){

htmlBuffer.append(line);

} else {

break;

}

}

} catch (IOException iox){

iox.printStackTrace( );

}

return htmlBuffer.toString( );

}

public Component getComponent( ) {

return new JScrollPane(htmlPane);

}

}

Example 12-21. Panel to contain the HTML display pane (continued)