Examples of java.beans.EventHandler

java.beans.EventHandler
alent code using an inner class instead of EventHandler. myButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { frame.toFront(); } }); The next simplest use of EventHandler is to extract a property value from the first argument of the method in the listener interface (typically an event object) and use it to set the value of a property in the target object. In the following example we create an ActionListener that sets the nextFocusableComponent property of the target (myButton) object to the value of the "source" property of the event.
```
 EventHandler.create(ActionListener.class, myButton, "nextFocusableComponent", "source") 
```
This would correspond to the following inner class implementation:
```
 //Equivalent code using an inner class instead of EventHandler. new ActionListener() { public void actionPerformed(ActionEvent e) { myButton.setNextFocusableComponent((Component)e.getSource());  } } 
```
It's also possible to create an EventHandler that just passes the incoming event object to the target's action. If the fourth EventHandler.create argument is an empty string, then the event is just passed along:
```
 EventHandler.create(ActionListener.class, target, "doActionEvent", "") 
```
This would correspond to the following inner class implementation:
```
 //Equivalent code using an inner class instead of EventHandler. new ActionListener() { public void actionPerformed(ActionEvent e) { target.doActionEvent(e); } } 
```
Probably the most common use of EventHandler is to extract a property value from the source of the event object and set this value as the value of a property of the target object. In the following example we create an ActionListener that sets the "label" property of the target object to the value of the "text" property of the source (the value of the "source" property) of the event.
```
 EventHandler.create(ActionListener.class, myButton, "label", "source.text") 
```
This would correspond to the following inner class implementation:
```
 //Equivalent code using an inner class instead of EventHandler. new ActionListener { public void actionPerformed(ActionEvent e) { myButton.setLabel(((JTextField)e.getSource()).getText());  } } 
```
The event property may be "qualified" with an arbitrary number of property prefixes delimited with the "." character. The "qualifying" names that appear before the "." characters are taken as the names of properties that should be applied, left-most first, to the event object.
For example, the following action listener
```
 EventHandler.create(ActionListener.class, target, "a", "b.c.d") 
```
might be written as the following inner class (assuming all the properties had canonical getter methods and returned the appropriate types):
```
 //Equivalent code using an inner class instead of EventHandler. new ActionListener { public void actionPerformed(ActionEvent e) { target.setA(e.getB().getC().isD());  } } 
```
The target property may also be "qualified" with an arbitrary number of property prefixs delimited with the "." character. For example, the following action listener:
```
 EventHandler.create(ActionListener.class, target, "a.b", "c.d") 
```
might be written as the following inner class (assuming all the properties had canonical getter methods and returned the appropriate types):
```
 //Equivalent code using an inner class instead of EventHandler. new ActionListener { public void actionPerformed(ActionEvent e) { target.getA().setB(e.getC().isD());  } } 
```
As EventHandler ultimately relies on reflection to invoke a method we recommend against targeting an overloaded method. For example, if the target is an instance of the class MyTarget which is defined as:
```
 public class MyTarget { public void doIt(String); public void doIt(Object); } 
```
Then the method doIt is overloaded. EventHandler will invoke the method that is appropriate based on the source. If the source is null, then either method is appropriate and the one that is invoked is undefined. For that reason we recommend against targeting overloaded methods. @see java.lang.reflect.Proxy @see java.util.EventObject @since 1.4 @author Mark Davidson @author Philip Milne @author Hans Muller @version 1.21, 05/23/06

    /**
     * The test checks event handler accessors
     */
    public void testAccessors() {
        InvocationObject invocationObject = new InvocationObject();
        EventHandler handler = new EventHandler(invocationObject, "someText",
                "source.text", "actionPerformed");
        assertEquals(invocationObject, handler.getTarget());
        assertEquals("someText", handler.getAction());
        assertEquals("source.text", handler.getEventPropertyName());
        assertEquals("actionPerformed", handler.getListenerMethodName());
    }

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     * The test checks the method invoke() with null listener value
     */
    public void testNullListenerMethodName() throws Exception {
        InvocationObject invocationObject = new InvocationObject();


        EventHandler handler = new EventHandler(invocationObject, "someText",
                "source.text", null);


        Object proxy = EventHandler.create(ActionListener.class,
                invocationObject, "someText", "source.text");


        Method m = ActionListener.class.getMethod("actionPerformed",
                new Class[] { ActionEvent.class });
        handler.invoke(proxy, m, new Object[] { new ActionEvent(this, 0, "") });


        assertEquals(invocationObject.getSomeText(), getText());
    }

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     * The test checks the method invoke()
     */
    public void testInvoke() throws Exception {
        InvocationObject invocationObject = new InvocationObject();


        EventHandler handler = new EventHandler(invocationObject, "someText",
                "source.text", "actionPerformed");


        Object proxy = EventHandler.create(ActionListener.class,
                invocationObject, "someText", "source.text");


        Method m = ActionListener.class.getMethod("actionPerformed",
                new Class[] { ActionEvent.class });
        handler.invoke(proxy, m, new Object[] { new ActionEvent(this, 0, "") });


        assertEquals(invocationObject, handler.getTarget());
        assertEquals(invocationObject.getSomeText(), getText());
        try {
            handler.invoke(proxy, null, new Object[] { new ActionEvent(this, 0,
                    "") });
            fail("should throw NullPointerException");
        } catch (NullPointerException e) {
            // Expected
        }

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     * The test checks the method invoke() with null property name
     */
    public void testInvokeWithNullPropertyName() throws Exception {
        InvocationObject invocationObject = new InvocationObject();


        EventHandler handler = new EventHandler(invocationObject,
                "doSomething", null, null);


        Object proxy = EventHandler.create(SampleListener.class,
                invocationObject, "doSomething");


        Method m = SampleListener.class.getMethod("fireSampleEvent",
                new Class[] { SampleEvent.class });
        handler.invoke(proxy, m, new Object[] { new SampleEvent("") });


        assertEquals(invocationObject, handler.getTarget());
        assertEquals("doSomething", getMethodName());


        // Regression test for HARMONY-4033
        m = FredListener.class.getMethod("fireFredEvent",
                new Class[] { FredEvent.class });

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    public void testEventHandler() {
        MockTarget target = new MockTarget();
        String action = "text";
        String eventPropertyName = "source.label";
        String listenerMethodName = "propertyChange";
        EventHandler handler = new EventHandler(target, action,
                eventPropertyName, listenerMethodName);
        assertSame(target, handler.getTarget());
        assertSame(action, handler.getAction());
        assertSame(eventPropertyName, handler.getEventPropertyName());
        assertSame(listenerMethodName, handler.getListenerMethodName());
    }

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    public void testEventHandler_TargetNull() {
        String action = "text";
        String eventPropertyName = "source.label";
        String listenerMethodName = "propertyChange";
        try {
            EventHandler handler = new EventHandler(null, action,
                    eventPropertyName, listenerMethodName);
            fail("should throw NPE");
        } catch (NullPointerException e) {


        }

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    public void testEventHandler_ActionNull() {
        MockTarget target = new MockTarget();
        String eventPropertyName = "source.label";
        String listenerMethodName = "propertyChange";
        try {
            EventHandler handler = new EventHandler(target, null,
                    eventPropertyName, listenerMethodName);
            fail("should throw NPE");
        } catch (NullPointerException e) {


        }
        EventHandler handler = new EventHandler(target, "action",
                eventPropertyName, listenerMethodName);
        assertSame(target, handler.getTarget());
        assertEquals("action", handler.getAction());
        assertSame(eventPropertyName, handler.getEventPropertyName());
        assertSame(listenerMethodName, handler.getListenerMethodName());
    }

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     */
    public void testEventHandler_EventPropertyNull() {
        MockTarget target = new MockTarget();
        String action = "text";
        String listenerMethodName = "propertyChange";
        EventHandler handler = new EventHandler(target, action, null,
                listenerMethodName);
        assertSame(target, handler.getTarget());
        assertSame(action, handler.getAction());
        assertNull(handler.getEventPropertyName());
        assertSame(listenerMethodName, handler.getListenerMethodName());
    }

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     */
    public void testEventHandler_MethodNull() {
        MockTarget target = new MockTarget();
        String action = "text";
        String eventPropertyName = "source.label";
        EventHandler handler = new EventHandler(target, action,
                eventPropertyName, null);
        assertSame(target, handler.getTarget());
        assertSame(action, handler.getAction());
        assertSame(eventPropertyName, handler.getEventPropertyName());
        assertNull(handler.getListenerMethodName());
    }

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        PropertyChangeListener proxy = EventHandler.create(
                PropertyChangeListener.class, target, "setCalled");


        String action = "text";
        String eventPropertyName = "source.label";
        EventHandler handler = new EventHandler(target, action,
                eventPropertyName, null);
        Method listenerMethod = PropertyChangeListener.class.getMethod(
                "propertyChange", new Class[] { PropertyChangeEvent.class });
        PropertyChangeEvent event = new PropertyChangeEvent(button, "label",
                "1", "5");
        handler.invoke(proxy, listenerMethod, new Object[] { event });
        assertEquals(button.getLabel(), target.getText());
        Method equalsMethod = Object.class.getMethod("equals",
                new Class[] { Object.class });
        assertEquals(Boolean.FALSE, handler.invoke(proxy, equalsMethod,
                new String[] { "mock" }));
        // Test null method with non-proxy Object.
        handler = new EventHandler(new Object(), "a", "a", "a");
        try {
            handler.invoke(new Object(), null, new Object[] {});
            fail("should throw NPE.");
        } catch (NullPointerException e) {
            // expected;
        }
    }

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