What is the best way to compare several javabean properties?

Question

I need to compare dozens of fields in two objects (instances of the same class), and do some logging and updating in case there are differences. Meta code could look somethi

Answer 1

A broad thought:

Create a new class whose object takes the following parameters: the first class to compare, the second class to compare, and a lists of getter & setter method names for the objects, where only methods of interest are included.

You can query with reflection the object's class, and from that its available methods. Assuming each getter method in the parameter list is included in the available methods for the class, you should be able to call the method to get the value for comparison.

Roughly sketched out something like (apologies if it isn't super-perfect... not my primary language):

public class MyComparator
{
    //NOTE: Class a is the one that will get the value if different
    //NOTE: getters and setters arrays must correspond exactly in this example
    public static void CompareMyStuff(Object a, Object b, String[] getters, String[] setters)
    {
        Class a_class = a.getClass();
        Class b_class = b.getClass();

        //the GetNamesFrom... static methods are defined elsewhere in this class
        String[] a_method_names = GetNamesFromMethods(a_class.getMethods());
        String[] b_method_names = GetNamesFromMethods(b_class.getMethods());
        String[] a_field_names = GetNamesFromFields(a_class.getFields());

        //for relative brevity...
        Class[] empty_class_arr = new Class[] {};
        Object[] empty_obj_arr = new Object[] {};

        for (int i = 0; i < getters.length; i++)
        {
            String getter_name = getter[i];
            String setter_name = setter[i];

            //NOTE: the ArrayContainsString static method defined elsewhere...
            //ensure all matches up well...
            if (ArrayContainsString(a_method_names, getter_name) &&
                ArrayContainsString(b_method_names, getter_name) &&
                ArrayContainsString(a_field_names, setter_name)
            {
                //get the values from the getter methods
                String val_a = a_class.getMethod(getter_name, empty_class_arr).invoke(a, empty_obj_arr);
                String val_b = b_class.getMethod(getter_name, empty_class_arr).invoke(b, empty_obj_arr);
                if (val_a != val_b)
                {
                    //LOG HERE
                    //set the value
                    a_class.getField(setter_name).set(a, val_b);
                }
            } 
            else
            {
                //do something here - bad names for getters and/or setters
            }
        }
    }
}