way to initialize a javabean to random values

Question

I was looking for some utility class/code that would take a java bean and initialize all its values to random values. It could be done via reflection as some libraries already create the toString() or equals() methods. Is is useful while developing the UI to have some data for example.

Other possible nice to haves:

1. recursively initialize non primitive or simple (string, date) members too
2. initialize a collection of beans
3. maybe give some way to limit the values generated, for example for numbers we could give ranges, for strings regexps or wildcards...

somebody knows something like this? thanks

EDIT: resolving...Got Apocalisp's sample working and definitively is what I was looking for. It has some drawbacks IMHO:

• The library has a much larger scope than that use, but this is not a problem for me
• It's quite complicated to understand how to build the Arbitrary for your objects unless you invest some time to study the whole thing. This is a drawback.
• And it could be more succint I guess, but that is fine too.

thanks!

Answer 1

Take a look at Easy Random: https://github.com/j-easy/easy-random.

It allows you to populate a Java Object graph with random data.

Disclaimer: I'm the author of that library

Answer 2

While I did notice that this post may be a bit old, I just happened to have the same necessity, and none of the presented solutions quite seemed to solve it acceptably, so I did some quick-and-dirty fifteen-minute not-quite-generic utility method for generating randomly populated beans, which may or may not be useful for someone else who happens to have a similar problem:

import java.beans.PropertyDescriptor;
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Collection;
import java.util.Date;
import java.util.Random;

import org.springframework.beans.BeanUtils;

public class RandomBeanUtil {

    public static <T> Collection<T> generateTestData(Class<T> clazz, int quantity) {
        Collection<T> list = new ArrayList<T>();

        PropertyDescriptor[] descriptors = BeanUtils.getPropertyDescriptors(clazz);
        Random rand = new Random();

        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.HOUR, 0);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);
        cal.set(Calendar.MILLISECOND, 0);

        try {
            for (int i = 0; i != quantity; i++) {
                    T o = clazz.newInstance();

                    for (PropertyDescriptor descriptor : descriptors) {
                        Class<?> type = descriptor.getPropertyType();
                        if (String.class.isAssignableFrom(type)) {
                            descriptor.getWriteMethod().invoke(o, String.valueOf(new char[]{
                                    (char)('A' + rand.nextInt(26)), (char)('a' + rand.nextInt(26)) }));
                        } else if (Date.class.isAssignableFrom(type)) {
                            cal.add(Calendar.DATE, rand.nextInt(60) - 30);
                            descriptor.getWriteMethod().invoke(o, cal.getTime());
                        } else if (BigDecimal.class.isAssignableFrom(type)) {
                            descriptor.getWriteMethod().invoke(o, 
                                    new BigDecimal(rand.nextDouble() * 500).setScale(2, RoundingMode.HALF_UP));
                        }
                    }

                    list.add(o);
            }       
        } catch (Exception e) {
            // TODO: Improve exception handling
            throw new RuntimeException("Error while generating the bean collection", e);
        }

        return list;
    }

}