反射妙用-判断对象各成员是否为null

有时候大家会有判断新创建对象各成员是否为null的需求，通过反简单处理，可满足此需求：

import java.lang.reflect.Field;

/**
 * 
 * @author elitesunry
 * @mail [e-mail]
 * @create 2011-5-10 7:21:30
 */
public abstract class ContentNullComparable {

	public boolean isEmpty(Object obj) {
		return isContentEmpty(this.getClass(), obj);
	}

	private boolean isContentEmpty(Class<?> clazz, Object obj) {
		Field[] fields = clazz.getDeclaredFields();
		int nullFiledCount = 0;
		for (Field field : fields) {
			Object fileldValue = null;
			try {
				// 这里不对复杂成员对象做嵌套判断
				fileldValue = field.get(obj);
			} catch (Exception e) {
				// ignore
			}
			if (fileldValue == null) {
				nullFiledCount++;
				if (nullFiledCount == fields.length) {
					return true;
				}
			}
		}
		return false;
	}
}

继承此类即可：

/**
 * @author elitesunry
 * @mail [e-mail]
 * @create 2011-5-7 11:48:27
 */
public class EmptyClass {

	public static void main(String[] args) {
		A a1 = new A();
		System.out.println(a1.isEmpty(a1));
		A a2 = new A();
		a2.a = "value";
		System.out.println(a2.isEmpty(a2));
		A a3 = new A();
		a3.obj = new A();
		System.out.println(a3.isEmpty(a3));
	}
}

class A extends ContentNullComparable {
	String a;
	String b;
	A obj;
}

由于java的单继承特性，这样的做法可能会导致你的类不能继承其他的类，你可以采用代理对象的方式解决此问题：

class DelegateContentNullComparable extends ContentNullComparable {
...
}

class YourClass {
...
private DelegateContentNullComparable delegate;
...
delegate.isEmpty(...);
...
}