Example: Math question

MathQuestion.java

public class MathQuestion extends Component {
    
    @Element
    private SimpleLabel answer = new SimpleLabel();
    
    enum Operation {
        
        ADDITION("+") {
            @Override
            public long calculate(long val1, long val2) {
                return val1 + val2; 
            }
        },
        
        SUBTRACTION("-") {
            @Override
            public long calculate(long val1, long val2) {
                return val1 - val2; 
            }
        };
        
        private final String name;
        
        private Operation(String name) {
            this.name = name;
        }
        public abstract long calculate(long val1, long val2);
    }
    
    private Operation operation;
    
    @Attribute
    private long val1;
    
    @Attribute
    private long val2;
    
    @Attribute
    public String operation() {
        return operation.name;
    }
    
    public MathQuestion() {
        tryAgain();
    }
    
    @Remoted
    public void tryAgain() {
        Random rand = new Random();
        val1 = rand.nextInt(201) - 100;
        val2 = rand.nextInt(201) - 100;
        operation = Operation.values()[rand.nextInt(2)];
        answer.setValue("");
        refresh();
    }
    
    @Remoted
    public void guess(Long guess) {
        if (guess != null) {
            if (guess == operation.calculate(val1, val2)) {
                answer.setValue("Your answer was correct :-)");
            } else {
                answer.setValue("Your answer was incorrect :-(");
            }
            answer.refresh();
        }
    }
}

MathQuestion.xsl

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:data="http://example.com/2006/some-data"
xmlns:txt="http://contextfw.net/ns/txt">

<xsl:template match="MathQuestion">
	<div id="{@id}"><xsl:call-template name="MathQuestion" /></div>
</xsl:template>

<xsl:template match="MathQuestion.update">
	<replaceInner id="{@id}"><xsl:call-template name="MathQuestion" /></replaceInner>
</xsl:template>

<xsl:template name="MathQuestion">
	<xsl:value-of select="@val1" />
	&#160; 
	<xsl:value-of select="@operation" />
	&#160;
	<xsl:value-of select="@val2" />
	&#160; = &#160;
	<input type="text" size="3" id="{@id}_guess" />
	<input type="button" class="button" value="Answer"
		onclick="contextfw.call('{@id}', 'guess', $('#{@id}_guess').val());" />
	&#160;<xsl:apply-templates select="answer" />
	<br/>
	<input type="button" class="button" value="Try again"
		onclick="contextfw.call('{@id}', 'tryAgain');" />
		
</xsl:template>

</xsl:stylesheet>