Commons method to test for an empty Java object graph?

Question

I've found myself writing a method like this:

boolean isEmpty(MyStruct myStruct) {
  return (myStruct.getStringA() == null || myStruct.getStringA().isEmpty())
    && (myStruct.getListB() == null || myStruct.getListB().isEmpty());
}

And then imagine this struct with lots of other properties and other nested lists, and you can imagine that this method gets very big and is tightly coupled to the data model.

Does Apache Commons, or Spring, or some other FOSS utility have the ability to recursively reflectively walk an object graph and determine that it's basically devoid of any useful data, other than the holders for Lists, Arrays, Maps, and such? So that I can just write:

boolean isEmpty(MyStruct myStruct) {
  return MagicUtility.isObjectEmpty(myStruct);
}

Answer 1

Thanks to Vladimir for pointing me in the right direction (I gave you an upvote!) although my solution uses PropertyUtils rather than BeanUtils

I did have to implement it but it wasn't hard. Here's the solution. I only did it for Strings and Lists since that's all I happen to have at the moment. Could be extended for Maps and Arrays.

import java.lang.reflect.InvocationTargetException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.commons.beanutils.PropertyUtils;
import org.apache.commons.lang.StringUtils;

public class ObjectUtils {

  /**
   * Tests an object for logical emptiness. An object is considered logically empty if its public gettable property
   * values are all either null, empty Strings or Strings with just whitespace, or lists that are either empty or
   * contain only other logically empty objects.  Currently does not handle Maps or Arrays, just Lists.
   * 
   * @param object
   *          the Object to test
   * @return whether object is logically empty
   * 
   * @author Kevin Pauli
   */
  @SuppressWarnings("unchecked")
  public static boolean isObjectEmpty(Object object) {

    // null
    if (object == null) {
      return true;
    }

    // String
    else if (object instanceof String) {
      return StringUtils.isEmpty(StringUtils.trim((String) object));
    }

    // List
    else if (object instanceof List) {
      boolean allEntriesStillEmpty = true;
      final Iterator<Object> iter = ((List) object).iterator();
      while (allEntriesStillEmpty && iter.hasNext()) {
        final Object listEntry = iter.next();
        allEntriesStillEmpty = isObjectEmpty(listEntry);
      }
      return allEntriesStillEmpty;
    }

    // arbitrary Object
    else {
      try {
        boolean allPropertiesStillEmpty = true;
        final Map<String, Object> properties = PropertyUtils.describe(object);
        final Iterator<Entry<String, Object>> iter = properties.entrySet().iterator();
        while (allPropertiesStillEmpty && iter.hasNext()) {
          final Entry<String, Object> entry = iter.next();
          final String key = entry.getKey();
          final Object value = entry.getValue();

          // ignore the getClass() property
          if ("class".equals(key))
            continue;

          allPropertiesStillEmpty = isObjectEmpty(value);
        }
        return allPropertiesStillEmpty;
      } catch (IllegalAccessException e) {
        throw new RuntimeException(e);
      } catch (InvocationTargetException e) {
        throw new RuntimeException(e);
      } catch (NoSuchMethodException e) {
        throw new RuntimeException(e);
      }
    }
  }

}

Answer 2

you can combine Appache Common StringUtils.isEmpty() method with BeanUtils.getProperties().