Java Swul Examples
Stratego -- Strategies for Program Transformation
Introduction
The examples covered in this page show some of the capabilities of Java-Swul. All the examples are based on code in thexmpl directory in the Java-Swul repository.
Nesting panels
The following Java-Swul code is taken from a file calledxmpl/Test3.javaswul in the Java-Swul package.
import javax.swing.*;
import java.awt.*;
public class Test3 {
public static void main(String[] ps) {
JFrame frame = frame {
title = "Welcome!"
content = panel of border layout {
center = label { text = "Hello World" }
south = panel of grid layout {
row = {
button { text = "cancel" }
button { text = "ok"}
}
}
}
};
frame.pack();
frame.setVisible(true);
}
}
When we assimilate/compile/run (swulc -i Test3.javaswul -o Test3.java && javac Test3.java && java Test3) this program this will produce:
The curious will immidiatly wonder what the command swulc -i Test3.javaswul -o Test3.java will produce in Test3.java. This is shown below.
import javax.swing.*;
import java.awt.*;
public class Test3
{
public static void main(String[] ps)
{
JButton jButton_1;
JButton jButton_0;
JPanel jPanel_1;
JLabel jLabel_0;
JPanel jPanel_0;
JFrame jFrame_0;
jFrame_0 = new JFrame();
jFrame_0.setTitle("Welcome!");
jPanel_0 = new JPanel();
BorderLayout borderLayout_0 = new BorderLayout();
jPanel_0.setLayout(borderLayout_0);
jFrame_0.setContentPane(jPanel_0);
JFrame frame = jFrame_0;
jLabel_0 = new JLabel();
jLabel_0.setText("Hello World");
jPanel_0.add(jLabel_0, BorderLayout.CENTER);
jPanel_1 = new JPanel();
GridLayout gridLayout_0 = new GridLayout(1, 2);
jButton_0 = new JButton();
jButton_0.setText("cancel");
jButton_1 = new JButton();
jButton_1.setText("ok");
jPanel_1.setLayout(gridLayout_0);
jPanel_1.add(jButton_0);
jPanel_1.add(jButton_1);
jPanel_0.add(jPanel_1, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
}
}
Menubar
The creating of menubars is an excellent example of where in Java the long list of statements becomes an unreadable and hard to understand mess. The best example is the url where Sun explains how to use Menus. This demostration menubar looks like this:
The code that generates this menu is not immidiatly clear in itself. Extra
measures are needed as you can see in the next code sniplet.
To accomplisch the same as shown in the above code sniplet you could
write in Java-Swul the following:
menu item {
text = "Both text and icon"
icon = "images/middle.gif"
mnemonic = b
}
menu item {
icon = "images/middle.gif"
mnemonic = d
}
menu separator
menu radiobutton {
text = "A radio button menu item"
group = a
selected = true
mnemonic = r
}
menu radiobutton {
text = "Another one"
mnemonic = o
group = a
}
Complete Java-Swul source and generated source can be downloaded.
- http://www.stratego-language.org//pub/Stratego/JavaSwulExamples/MenuLookDemo.javaswul
- http://www.stratego-language.org//pub/Stratego/JavaSwulExamples/MenuLookDemo.java (generated)
- http://java.sun.com/docs/books/tutorial/uiswing/components/example-1dot4/MenuLookDemo.java (from java.sun.com)
Events
To demonstrate how the events that the userinterface components generate can be handled in Java-Swul we take the following interface.
Event handlers are connected to the window, the file menu, an item in the file menu, to the button and to the slider. That an event from of user interface component shoud be listened to and how it should be handled is declared as a property of a Swul component. The right hand side of such a property is an block of Java statements. The following piece of code shows how the previous user interface is created and how the event handlers are declared.
import javax.swing.*;
import java.awt.*;
import java.beans.*;
import java.awt.event.*;
import javax.swing.event.*;
public class Test19 {
public static void main(String[] ps) {
JFrame frame = frame {
window event = { System.out.println("I'm a frame on fire!"); }
menubar = {
menu {
menu event = { System.out.println("Fired event: "+event.toString()); }
text = "File"
items = {
menu item {
text = "New"
action event = { System.out.println("Create something new"); }
}
menu item {
text = "Open"
}
}
}
}
content = panel of border layout {
south = button {
text = "Click-y-click"
action event = {
Test19.handleClick() ;
System.out.println("Click-y-click some more");
}
}
center = slider named aSlider {
change event = {
System.out.println(aSlider.getValue());
}
}
}
title = "Hello world"
};
frame.pack();
frame.setVisible(true);
}
public static void handleClick(){
System.out.println("Click-y-click once");
}
}
The event blocks are collected into a new innerclass that is created in the class where the events properties were declared. The components are connected to the methods in this new innerclass by the creation and connection of EventHandler objects. In this way only a single object is created to hold the reactions to events and the EventHandler uses proxies to create only a single object per eventtype. This reduces the footprint of the Java program when an eventtype accurs more then once compared to the classic method of using (annoymous-)innerclasses per event.
Some of the generated code to create and connect the components is shown here:
jFrame_0.addWindowListener ((WindowListener)EventHandler.create(WindowListener.class, classHandler_0, "windowListener_0", ""));
jMenu_0.addMenuListener ((MenuListener) EventHandler.create(MenuListener.class, classHandler_0, "menuListener_0", ""));
jMenuItem_0.addActionListener((ActionListener)EventHandler.create(ActionListener.class, classHandler_0, "actionListener_0", ""));
jButton_0.addActionListener ((ActionListener)EventHandler.create(ActionListener.class, classHandler_0, "actionListener_1", ""));
aSlider.addChangeListener ((ChangeListener)EventHandler.create(ChangeListener.class, classHandler_0, "changeListener_0", ""));
...
public static class ClassHandler_0 {
ClassHandler_0 () { }
public void changeListener_0(ChangeEvent event) {
System.out.println(aSlider.getValue());
}
public void actionListener_1(ActionEvent event) {
Test19.handleClick();
System.out.println("Click-y-click some more");
}
public void actionListener_0(ActionEvent event) {
System.out.println("Create something new");
}
public void menuListener_0(MenuEvent event) {
System.out.println("Fired event: " + event.toString());
}
public void windowListener_0(WindowEvent event) {
System.out.println("I'm a frame on fire!");
}
}
Complete Java-Swul source and generated source can be downloaded.
- http://www.stratego-language.org//pub/Stratego/JavaSwulExamples/Test19.javaswul
- http://www.stratego-language.org//pub/Stratego/JavaSwulExamples/Test19.java (generated)
Creating a GridBagLayout with ease
A GridBagLayout is in practice a complex layout. If you would create a layout of your components with this layoutmanager this often means calculation of cell locations and width/height values. Take for instance the following interface:
Components can span multiple cells. In the example they span horizontal,
vertical, both or neither. Java-Swul can calculate the values of the width,
height, x-position and y-position for you. The input for this calculation
is a more understandable way of writing down how the grid should be filled.
The above screen is the result of the following java / java-swul code.
Placement of components is closer to the concept that a gridlayout offers,
making it easier to create and alter a gridlayout.
import javax.swing.*;
import java.awt.*;
public class Test17 {
public static void main(String[] ps) {
JFrame f = frame {
title = "Welcome!"
content = panel of border layout {
center = panel of gridbag layout {
row = { new JButton("Button1") new JButton("Button2") <<< <<< }
row = { new JButton("Button3") <<< ___ new JButton("Button4") }
row = { ___ new JButton("Button5") new JButton("Button6") ^^^ }
row = { new JButton("Button7") <<< new JButton("Button8") ^^^ }
row = { ^^^ ___ new JButton("Button9") <<< }
}
}
};
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.pack();
f.setSize(f.getPreferredSize());
f.setVisible(true);
}
}
Complete Java-Swul source and generated source can be downloaded.
- http://www.stratego-language.org//pub/Stratego/JavaSwulExamples/Test17.javaswul
- http://www.stratego-language.org//pub/Stratego/JavaSwulExamples/Test17.java
Widget-o-rama
The next screenshot is from a file calledxmpl/Test16.javaswul in the Java-Swul package.
The Java-Swul source used to create this crowded interface contains the next code-example.
The surrounding Java code is left out to save some space. The complete Java code is further down on
this page.
this {
title = "Welcome"
content = panel {
border = raised bevel border
layout = border layout {
north = scrollpane of panel of grid layout {
row = { textarea {
rows = 10
columns = 10
text = "A 10 by 10 textarea"
}
tree { }
}
}
center = panel of grid layout {
row = {
label {
text = "This an JLabel"
}
button {
text = "This is a JButton"
}
slider {
}
}
row = {
radiobutton {
text = "JRadioButton in a group"
group = radiogroup1
selected = true
}
textfield {
text = "a JTextField"
}
progressbar {
value = 23
}
}
row = {
checkbox {
text = "a JCheckBox in a group"
}
combobox {
}
togglebutton {
text = "a JToggleButton"
group = someGroup
}
}
row = {
radiobutton {
text = "another JRadioButton"
group = radiogroup1
}
label {
}
togglebutton {
text = "another JToggleButton"
group = someGroup
selected = true
}
}
}
}
}
};
As you can see it is quite verbose. Writing things down in this structured way causes lots of lines with just an } and spaces.
Java-Swul has some sugur to it. The line scrollpane of panel of grid layout { row = { ... } } is short for:
scrollpane {
content = panel {
layout = grid layout {
row = { ... }
}
}
}
So you can skip nestings that are acceptable with default properties.
Complete Java-Swul source and generated source can be downloaded.
- http://www.stratego-language.org//pub/Stratego/JavaSwulExamples/Test16.javaswul
- http://www.stratego-language.org//pub/Stratego/JavaSwulExamples/Test16.java