Java Beans, Reflection and Annotations

Using NetBeans create a Java Bean named TempLabel that implements a temperature converter from Celsius to Farenheit. This Bean must extend JLabel redefining the setText method in such a way that setText("c") visualizes the value obtained by converting c into Farenheit.

To test the code write a main program that generates a number of Celsius values and, prints each of them along with its corresponding Farenheit value (obtained using the setText/getText methods of TempLabel).

• Goal: Warming up!
• Expected output: A working TempLabel for the next exercise.

Export the TempLabel bean of the Exercise 1 in a jar file and import it inside the bean palette of NetBeans. In a new project, create a class that extends a JFrame. Add to this frame a JText, a JButton and a TempLabel bean. The last bean is not be visible, but you can act on it using the Navigator window of NetBeans.

Complete the small application so that the user writes a temperature in the JText and then clicks on the button to show in the TempBean the corresponding Farenheit value. Inspect the code generated by NetBeans. Save the developed bean in a jar file.

• Goal: Using simple beans and programming their interactions for developing more complex beans.
• Expected output: The jar file containing the bean, executable with java -jar ...

Write a Java program that takes as argument from the command line the name of a Java Bean class and inspects it by using the reflection API. Your program must print:

• the properties and their capabilities (read-only, read-write);
• the events it permits to subscribe.

Test your program with the bean developed in Exercise 2 and with beans from the standard library, as AbstractButton, JButton, JFrame, etc..

• Goal: Learning the Java Reflection API. Understanding the role of introspection in NetBeans.
• Expected output: A working class implementing the specification

Extend the TempBean of Exercise 1 making text a constrained property, to validate the provided input. The bean should register itself as VetoableChangeListener, and it should block any attempt to set the text property if the provided string does not represent a double or if its value is smaller than the absolute 0 (-273,15 celsius degrees).

Make a copy of the source code of Exercise 2, and reengineer it in order to include the new bean in place of the original TempBean.

• Goal: Working with constrained properties. Understanding the cost of replacing a bean.
• Expected output: The jar file containing the bean, executable with java -jar ...

Being an instructor is an hard work! Luckily, you can help us by writing a software that automates the testing of your programs :P

For that, define a new Java annotation @Test and a Main program as follows:

• @Test stores the expected result of the method it annotates (for simplicity, we assume a constant result) and must be visible at runtime.
• Main takes as argument from the command line the name of a Java class and, using reflection, runs all the methods that are annotated with @Test. Print OK if the result matches the expectations, KO otherwise.

• Goal: Experimenting with reflection and annotations.
• Expected output: A working program meeting the requirements.