Compiler Design-Reflection ProjectCompiler Design dersindeki katkılarından dolayı
Prf.Dr.M.Akif Eyler'e teşekkür ediyoruz.
SIMPLE REFLECTION APPLICATION
Project Definition : This project is a simple application of the reflection stuff.
Project Purpose : The input string is controlled as if it is a field of the Color class and changes a panel’s color to corresponding input value.
Reflection : Reflection is a programming paradigm which is used for self-optimization to application programs and to improve their flexibility. The reflective paradigm introduces meta-information which keeps knowledge about compound operations. Meta-information is name of the field, method and class and so on.
A reflective program optimizes or modifies its own memory area. Reflection also can be used to adapt an existing system dynamically to different situations.
Some features of reflection are:
1) Discover and Modify source code constructions.
2) Convert a string matching of a class or function into a reference to or invocation of that class or function.
3) Evaluate a string as if it were a source code statement at run-time.
We used the second feature of the features shown above. The field of the Color class can be retrieved as string and use to colors the panel.
We also use reflection for serialization, expression evaluation, language interpretation, class factories, object description, plug-in architectures. Reflection is one of the most exciting features of Java.
Big industrial-strength protocols like SOAP and JavaBeans wouldn't be possible if it weren't for Reflection. Every time you drag-and-drop an object in your favorite IDE into a form, Reflection is orchestrating the action behind the scenes..
Reflection is an advanced feature of the Java environment. It gives runtime information about objects, classes, and interfaces.
Disadvantages and Misuses of Reflection
As we mentioned in the proposal, there are some disadvantages of reflection. We would have used “invoke” method to call event handler method “actionPerformed” but we thought this would be a misuse and not show the necessity of reflection.
About Project: Reflection can be used in very different contexts to achieve completely different results. We wanted to have a function to convert strings into colors. The strings you'd like to pass are color names, and the function should return the appropriate color:
Color myColor = ColorWorks. getColorName( "black" );// myColor will contain the color Color.black
If you don't use Reflection, you have to maintain a mapping structure that relates color names to Color objects. If the folks at Sun decide tomorrow to introduce new 10,000 Color constants, the map will be enormous. That was actually our first thought about reflection when we decided our project. On the other hand, we thought what can we done in such situation and whether there is a solution without reflection or not. Because reflection should be used only if there is no solution without it as we mentioned in the proposal.
This is where we can utilize reflection to analyze the Color class and find its Color constant names and their values.
Project Without Reflection : As we mentioned before, there must be a predefined mapping structure but this is not a good solution for changing data or information. Therefore, reflection will be a nice.
What Have We Learned : We have learned that using reflection in such situation makes you avoid from changing the code in the class when the reflected class’s fields change. Because its fields are determined in run-time.
When we were searching on the internet, we have also learned that even event handler methods can be invoked via reflection but we did not need to use it.
Summary : Java reflection gives us a meta-language to ask questions and manipulate classes, interfaces, and objects.
There are a lot of features of this paradigm but we used only one of them. We learned where to use and not to use reflection.
References :
http://en.wikipedia.org/wiki/Reflection_%28computer_science%29 http://java.sun.com/j2se/1.3/docs/api/java/lang/reflect/package-summary.html Note:Please visit
http://sss.eng.marmara.edu.tr/download.html page and see for what type of applications our instructor writes about.
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