Pitfalls of Reflection

In this post I will discuss a pitfall of the use of reflection in Java. Specifically how reflection can obscure and even change the semantics of a piece of code.

What is wrong with the following example of JavaBean naming convention?

public Boolean isCorrect() {
    /* implementation not shown. */
}

Did you spot the capital B on the Boolean return type? According to the JavaBean naming convention the property does not fall under the special rules for booleans and should be named accordingly.

public Boolean getCorrect() {
    /* implementation not shown. */
}

Although there is a sleight syntactic difference, the apparent semantic difference is non-existent. According to William Shakespeare:

A rose by any other name would smell as sweet

Enter reflection. By using reflection it is possible to perform hugely different behaviour depending on the name of a method. The following whimsical example is a clear demonstration of this fact.

Class aClass = ReflectedClass.class;
Method method;
try
{
    method = aClass.getDeclaredMethod("isCorrect");
    protect(Planet.EARTH);
}
catch (NoSuchMethodException e)
{
    destroy(Planet.EARTH);
}

So one of the pitfalls of reflection is the hidden semantics associated with code. Stated in other words: the influence of code can not be inferred by the syntactic definition of that code.

Qwickie: a usefull eclipse plugin for Wicket Development

In this post I will introduce Qwickie, a usefull eclipse plugin for Wicket Development.

In my daily work I develop software applications. As a web framework we use Wicket, a component based framework with a clear separation of the presentation and the logic.

The connection you between presentation and logic is made via "wicket:id"'s. (See the wicket examples page how this is done.) I found myself executing the following behavioural pattern or it's inverse a lot.

1. Seek a wicket:id in a webpage
2. Find corresponding wicket:id in the code

Recently I came across a nice little eclipse plugin which speeds up this pattern. It is named Qwickie, and it facilitates the following use cases:

• Navigate from java code elements to the corresponding html element via wicket:id
• Show the corresponding html fragment from the java code element

Both actions are performed by clicking the wicket:id while holding down the ctrl button. This shaves off time following the association between presentation and logic.