Skip to main content

Java Reflections


Java Reflections is one of the most powerful API in Java. Java Reflection API allows us to access metadata about the classes at runtime i.e. Reflections allows us to find out constructors, fields and methods from a Java class.
In this post I will show how to find out constructors, fields and methods from a Java class.

Constructors
Following code shows how to find out constructors from a class

Constructor constructors[]=java.lang.String.class.getDeclaredConstructors();
// getDeclaredConstructors() returns all the constructors which are defined in this class including private.
// it will not return constructors from base class.

Constructor constructors[]=java.lang.String.class.getConstructors();
// getConstructors() returns all the constructors including constructors from base class also, although this will
// not return any private or protected constructors.


for(Constructor cc:constructors){
System.out.println(cc);
}

Methods
Following code shows how to find out methods from a class

Method methods[]=java.lang.String.class.getDeclaredMethods();
// same as constructors getDeclaredMethods() returns all the methods from a class including private.
// it will not return methods from base class.

Method methods[]=java.lang.String.class.getMethods[];
// getMethods() will return public methods from this class and base class.


for(Method method:methods){
System.out.println(
}

Fields
Following code shows how to find out fields from a class

Field fields[]=java.lang.String.class.getDeclaredFields();
// same as above getDeclaredFields returns all methods(public, private and protected) from this class only.

Field fields[]=java.lang.String.class.getFields();
// getFields will return public fields from this and base class.

With these following are the methods which returns exact constructor, field and method, we need to pass parameter types to get exact respective element.

// getConstructor
Constructor c=java.lang.String.class.getConstructor(new Class[]{String.class});

// getMethod
Method method=java.lang.String.class.getMethod("equals", new Class[]{String.class});

// getField
Field field=SomeClass.class.getField("nameOfField");

Comments

Popular posts from this blog

Spring AOP : JDK Proxy vs CGLib Proxy

Spring framework is one of the most widely used framework in Enterprise application development. It has so many features such as Dependency injection, Data access integration, MVC, AOP which takes care of most of the boilerplate part of project, and developers can then focus on business logic only.

One of the important feature in Spring is AOP. It is used by almost every enterprise application which is being developed using Spring.

AOP So what is AOP? Definition of AOP -
Aspect oriented programming is a programming paradigm which aims to increase modularity by allowing the separation of cross cutting concerns. Well, my understanding of AOP is - AOP allows us to introduce/join new modules in your project at pre-specified dynamic locations without having to code for it. Traditional examples of AOP is Transaction management, logging etc. You can read more about AOP at here.

This article is for those who know AOP, have used AOP in their projects but do not know how Spring or other DI fra…

Java Tools Plugin for Notepad++

This post and the plugin is outdated. Please use plugin from this link which is updated and allows customization of shortcut key mappings and much more.
Notepad++ is a great free editor. I like notepad++ because its a light weight editor and loads instantly. I use notepad++ for editing many files everyday. One plugin I always wanted was a plugin which lets me compile my java files and execute them from editor itself, but I couldn't find it so I wrote a myself. This plugin can be downloaded from this link.
I am working on this plugin to make it more effective, so that if user have more than one installations of JDK or JRE then user should be able to choose which one to use etc.
This is a simple plugin which has two commands-
Compile - compiles a java file.
Run - executes a java file.
For using this plugin Java must be installed on the system.

Notepad++ Compile and Run Java Programs

Notepad++ is a great file editor. It has many features. The most important feature which I like about Notepad++ is its light weight. It loads up so quickly, that's great. It also provides syntax highlighting for many languages. I use notepad++ to edit general files as well as my simple Java programs.
Although notepad++ provides functionality to run external programs, I prefer NppJavaTools plugin to compile and run Java programs using notepad++.
You can download NppJavaTools plugin from this page - NppJavaTools.

Installation
Installation of plugins in notepad++ is very simple process. All you have to do is copy plugin dll into plugins folder of notepad++ installation directory and restart the notepad++.

Features
This plugin provides following features,


Compile and run your Java files within Notepad++Set custom hotkeys for compiling and running Java CodeLibrary support Compile and RunThis function allows you to run your Java programs to compile and run from Notepad++. Set Custom hotkeysThi…