Java Code House

In our last post we were only concerned in retrieving the declaration details of any class. Today I will go further and try to sniff inside any class. So today I will show you how you can retrieve all the constructors, fields and methods of any class using Java Reflection. For now we will only try to discover all the public members of a class and deal with private ones later. The java.lang.Class provides suitable methods for discovering the members. Here in our sample code we will first take as input the concerned class name and load it using Class.forName(). Then in order to get all its public constructors we vwill use getConstructors(), for fields use getFields() and for methods use getMethods(). An important thing to mention here is that these will return all the public members declared in that class as well as those inherited from its parent. You wont be able to retrieve the private members declarec using these methods. In order to get private members also use getDeclaredConstructors(), getDeclaredFields() and getDeclaredMethods(); but in this case you wont be able to get the inherited members.
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import static java.lang.System.out;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

public class ClassSniffer {
        public static void main(String[] args) {
        out.print("Enter Class Name : ");
        String cname=System.console().readLine();
        try {
        Class c=Class.forName(cname);
        out.println("\n------OUTPUT------");
            //getting all constructors
        out.println("\nConstructors : ");
            Constructor<?> cons[]=c.getConstructors();
            for(Constructor<?> con : cons)
                 out.println("  "+con);
            //getting all fields
            out.println("\nFields : ");
            Field fs[]=c.getFields();
            if(fs.length>0)
                for(Field f : fs)
                      out.println("  "+f);
            else
                out.println("  --No Fields Declared--");
            //getting all methods
            out.println("\nMethods : ");
            Method ms[]=c.getMethods();
            for(Method m : ms)
                     out.println("  "+m);
   } catch (ClassNotFoundException e) {
          e.printStackTrace();
   }
}
}