Commons方法测试一个空的Java对象图？

Question

我发现自己写的方法是这样的:

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

然后想象这个结构有很多其他属性和其他嵌套列表,你可以想象这个方法变得非常大并且与数据模型紧密耦合.

Apache Commons,或Spring,或其他一些FOSS实用程序是否能够递归反射地遍历对象图并确定它基本上没有任何有用的数据,除了列表,数组,地图等的持有者？所以我可以写:

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

Answer 1

感谢弗拉基米尔指出我正确的方向(我给了你一个upvote!)虽然我的解决方案使用PropertyUtils而不是BeanUtils

我确实必须实现它,但并不难.这是解决方案.我只为字符串和列表做过,因为那是我现在碰巧遇到的.可以扩展为地图和数组.

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);
      }
    }
  }

}