BeanUtils(空值空集合空List再也不復制)

BeanUtils.copyProperties使用的時候，空值也被拷貝使它邊的很雞肋。

下面對他進行擴展，支持多種空值再也不拷貝

public abstract class BeanUtils extends org.springframework.beans.BeanUtils {  
    
    public static void copyProperties(Object source, Object target) throws BeansException {  
      Assert.notNull(source, "Source must not be null");  
      Assert.notNull(target, "Target must not be null");  
      Class<?> actualEditable = target.getClass();  
      PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);  
      for (PropertyDescriptor targetPd : targetPds) {  
        if (targetPd.getWriteMethod() != null) {  
          PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());  
          if (sourcePd != null && sourcePd.getReadMethod() != null) {  
            try {  
              Method readMethod = sourcePd.getReadMethod();  
              if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {  
                readMethod.setAccessible(true);  
              }  
              Object value = readMethod.invoke(source); 
             
              
              // 這裏判斷如下value是否爲空 固然這裏也能進行一些特殊要求的處理 例如綁定時格式轉換等等  
              if (value != null) {  
                  boolean isEmpty = false;
                    if (value instanceof Set) {
                        Set s = (Set) value;
                        if (s == null || s.isEmpty()) {
                            isEmpty = true;
                        }
                    } else if (value instanceof Map) {
                        Map m = (Map) value;
                        if (m == null || m.isEmpty()) {
                            isEmpty = true;
                        }
                    } else if (value instanceof List) {
                        List l = (List) value;
                        if (l == null || l.size() < 1) {
                            isEmpty = true;
                        }
                    } else if (value instanceof Collection) {
                        Collection c = (Collection) value;
                        if (c == null || c.size() < 1) {
                            isEmpty = true;
                        }
                    }
                  
                if (!isEmpty) { 
                Method writeMethod = targetPd.getWriteMethod();  
                if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {  
                  writeMethod.setAccessible(true);  
                }  
                writeMethod.invoke(target, value);  
              }  
              }
            } catch (Throwable ex) {  
              throw new FatalBeanException("Could not copy properties from source to target", ex);  
            }  
          }  
        }  
      }  
    }  
  }