每日技术干货，第一时间送达！
耗时8个月联合打造 《 2023年Java高薪课程 》，已更新了 102G 视频，累计更新时长 500+ 个小时，需要的小伙伴可以了解下，一次购买，持续更新，无需2次付费。
前言
对象拷贝
-
浅拷贝：对基本数据类型进行值传递，对引用数据类型进行引用传递般的拷贝，此为浅拷贝 -
深拷贝：对基本数据类型进行值传递，对引用数据类型，创建一个新的对象，并复制其内容，此为深拷贝。
deep and shallow copy
BeanUtils
首先来看一个非常简单的BeanUtils的例子
public class PersonSource { private Integer id; private String username; private String password; private Integer age; // getters/setters omiited } public class PersonDest { private Integer id; private String username; private Integer age; // getters/setters omiited } public class TestApacheBeanUtils { public static void main(String[] args) throws InvocationTargetException, IllegalAccessException { //下面只是用于单独测试 PersonSource personSource = new PersonSource(1, "pjmike", "12345", 21); PersonDest personDest = new PersonDest(); BeanUtils.copyProperties(personDest,personSource); System.out.println("persondest: "+personDest); } } persondest: PersonDest{id=1, username='pjmike', age=21} //将源对象中的值拷贝到目标对象 public static void copyProperties(Object dest, Object orig) throws IllegalAccessException, InvocationTargetException { BeanUtilsBean.getInstance().copyProperties(dest, orig); } org.apache.commons.beanutils.BeanUtils对复杂对象的复制是引用，这是一种浅拷贝。
Ali-Check | 避免用Apache Beanutils进行属性的copy。
public void copyProperties(final Object dest, final Object orig) throws IllegalAccessException, InvocationTargetException { // Validate existence of the specified beans if (dest == null) { throw new IllegalArgumentException ("No destination bean specified"); } if (orig == null) { throw new IllegalArgumentException("No origin bean specified"); } if (log.isDebugEnabled()) { log.debug("BeanUtils.copyProperties(" + dest + ", " + orig + ")"); } // Copy the properties, converting as necessary if (orig instanceof DynaBean) { final DynaProperty[] origDescriptors = ((DynaBean) orig).getDynaClass().getDynaProperties(); for (DynaProperty origDescriptor : origDescriptors) { final String name = origDescriptor.getName(); // Need to check isReadable() for WrapDynaBean // (see Jira issue# BEANUTILS-61) if (getPropertyUtils().isReadable(orig, name) && getPropertyUtils().isWriteable(dest, name)) { final Object value = ((DynaBean) orig).get(name); copyProperty(dest, name, value); } } } else if (orig instanceof Map) { @SuppressWarnings("unchecked") final // Map properties are always of type <String, Object> Map<String, Object> propMap = (Map<String, Object>) orig; for (final Map.Entry<String, Object> entry : propMap.entrySet()) { final String name = entry.getKey(); if (getPropertyUtils().isWriteable(dest, name)) { copyProperty(dest, name, entry.getValue()); } } } else /* if (orig is a standard JavaBean) */ { final PropertyDescriptor[] origDescriptors = getPropertyUtils().getPropertyDescriptors(orig); for (PropertyDescriptor origDescriptor : origDescriptors) { final String name = origDescriptor.getName(); if ("class".equals(name)) { continue; // No point in trying to set an object's class } if (getPropertyUtils().isReadable(orig, name) && getPropertyUtils().isWriteable(dest, name)) { try { final Object value = getPropertyUtils().getSimpleProperty(orig, name); copyProperty(dest, name, value); } catch (final NoSuchMethodException e) { // Should not happen } } } } } Spring 的 BeanUtils
public class TestSpringBeanUtils { public static void main(String[] args) throws InvocationTargetException, IllegalAccessException { //下面只是用于单独测试 PersonSource personSource = new PersonSource(1, "pjmike", "12345", 21); PersonDest personDest = new PersonDest(); BeanUtils.copyProperties(personSource,personDest); System.out.println("persondest: "+personDest); } } copyProperties方法进行拷贝，只不过它的实现方式非常简单，就是对两个对象中相同名字的属性进行简单的get/set，仅检查属性的可访问性。具体实现如下:
private static void copyProperties(Object source, Object target, @Nullable Class<?> editable, @Nullable 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<String> 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); } } } } } } 小结
【福利】2023 高薪课程，全面来袭（视频+笔记+源码）
往期推荐