三种复制属性的工具

1.cglib

import net.sf.cglib.beans.BeanCopier;BeanCopier copier = BeanCopier.create(User.class, User.class, false);copier.copy(source, user, null);

2.org.apache.commons

import org.apache.commons.beanutils.BeanUtils;BeanUtils.copyProperties(user, source);

3.spring beans

org.springframework.beans.BeanUtils.copyProperties(source, user);

效率方面:

spring beans>=cglib>org.apache.commons.beanutils.BeanUtils

org.springframework.beans.BeanUtils与net.sf.cglib.beans.BeanCopier

在同一个数量级,区别不大,比org.apache.commons.beanutils.BeanUtils效率快一个数量级.

org.springframework.beans.BeanUtils.copyProperties最终调用的是以下这个方法.

/**	 * Copy the property values of the given source bean into the given target bean.	 * 
Note: The source and target classes do not have to match or even be derived	 * from each other, as long as the properties match. Any bean properties that the	 * source bean exposes but the target bean does not will silently be ignored.	 * @param source the source bean	 * @param target the target bean	 * @param editable the class (or interface) to restrict property setting to	 * @param ignoreProperties array of property names to ignore	 * @throws BeansException if the copying failed	 * @see BeanWrapper	 */	private static void copyProperties(Object source, Object target, Class
      editable, String... ignoreProperties)			throws BeansException {		Assert.notNull(source, "Source must not be null");		Assert.notNull(target, "Target must not be null");		Class
      actualEditable = target.getClass();		if (editable != null) {			if (!editable.isInstance(target)) {				throw new IllegalArgumentException("Target class [" + target.getClass().getName() +						"] not assignable to Editable class [" + editable.getName() + "]");			}			actualEditable = editable;		}		PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);		List
     
       ignoreList = (ignoreProperties != null ? Arrays.asList(ignoreProperties) : null);		for (PropertyDescriptor targetPd : targetPds) {			Method writeMethod = targetPd.getWriteMethod();			if (writeMethod != null && (ignoreList == null || !ignoreList.contains(targetPd.getName()))) {				PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());				if (sourcePd != null) {					Method readMethod = sourcePd.getReadMethod();					if (readMethod != null &&							ClassUtils.isAssignable(writeMethod.getParameterTypes()[0], readMethod.getReturnType())) {						try {							if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {								readMethod.setAccessible(true);							}							Object value = readMethod.invoke(source);							if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {								writeMethod.setAccessible(true);							}							writeMethod.invoke(target, value);						}						catch (Throwable ex) {							throw new FatalBeanException(									"Could not copy property '" + targetPd.getName() + "' from source to target", ex);						}					}				}			}		}	}
     

之前以为bean中有bean或List的会递归调用,实际上并没有.用反射调用read method和write method.