Get the class instance variables and print their values using reflection

Question

I have a 2 POJO classes with getters and setters,now i am trying to get all the class instance variables of that class.

I got to know that we can use reflection how to do it?

This is my POJO Class which will extend my reflection class.

class Details{

private int age;
private String name;

}

Reflection class is like this:

class Reflection{

public String toString(){

return all the fields of that class
}

Answer 1

You could do something like this:

public void printFields(Object obj) throws Exception {
    Class<?> objClass = obj.getClass();

    Field[] fields = objClass.getFields();
    for(Field field : fields) {
        String name = field.getName();
        Object value = field.get(obj);

        System.out.println(name + ": " + value.toString());
    }
}

This would only print the public fields, to print private fields use class.getDeclaredFields recursively.

Or if you would extend the class:

public String toString() {
    try {
        StringBuffer sb = new StringBuffer();
        Class<?> objClass = this.getClass();

        Field[] fields = objClass.getFields();
        for(Field field : fields) {
            String name = field.getName();
            Object value = field.get(this);

            sb.append(name + ": " + value.toString() + "\n");
        }

        return sb.toString();
    } catch(Exception e) {
        e.printStackTrace();
        return null;
    }
}

Answer 2

    ClassLoader classLoader = Main.class.getClassLoader();
    try {
        Class cls = classLoader.loadClass("com.example.Example");
        Object clsObject = cls.newInstance();

        Field[] fields = cls.getFields();
        for (Field field : fields) {
            String name = field.getName();
            Object value = field.get(clsObject);

            System.out.println("Name : "+name+" Value : "+value);

        }
        System.out.println(cls.getName());


    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (InstantiationException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }