java 对象之间属性值复制

java对象之间属性值复制在许多开源框架中也有实现，在这里介绍下自己的实现、apache commons-beanutils、Spring三种方式实现。

1 自己实现。采用反射，通过源对象getter 方法获取属性值，并通过目标对象的setter方法设置到目标对象中去。没有考虑太多性能，如果需要批量或者经常性执行该操作，建议不采用此种实现。下面给出源码：

/** * 利用反射实现对象之间属性复制 * @param from * @param to */public static void copyProperties(Object from, Object to) throws Exception {copyPropertiesExclude(from, to, null);}/** * 复制对象属性 * @param from * @param to * @param excludsArray 排除属性列表 * @throws Exception */@SuppressWarnings("unchecked")public static void copyPropertiesExclude(Object from, Object to, String[] excludsArray) throws Exception {List<String> excludesList = null;if(excludsArray != null && excludsArray.length > 0) {excludesList = Arrays.asList(excludsArray);//构造列表对象}Method[] fromMethods = from.getClass().getDeclaredMethods();Method[] toMethods = to.getClass().getDeclaredMethods();Method fromMethod = null, toMethod = null;String fromMethodName = null, toMethodName = null;for (int i = 0; i < fromMethods.length; i++) {fromMethod = fromMethods[i];fromMethodName = fromMethod.getName();if (!fromMethodName.contains("get"))continue;//排除列表检测if(excludesList != null && excludesList.contains(fromMethodName.substring(3).toLowerCase())) {continue;}toMethodName = "set" + fromMethodName.substring(3);toMethod = findMethodByName(toMethods, toMethodName);if (toMethod == null)continue;Object value = fromMethod.invoke(from, new Object[0]);if(value == null)continue;//集合类判空处理if(value instanceof Collection) {Collection newValue = (Collection)value;if(newValue.size() <= 0)continue;}toMethod.invoke(to, new Object[] {value});}}/** * 对象属性值复制，仅复制指定名称的属性值 * @param from * @param to * @param includsArray * @throws Exception */@SuppressWarnings("unchecked")public static void copyPropertiesInclude(Object from, Object to, String[] includsArray) throws Exception {List<String> includesList = null;if(includsArray != null && includsArray.length > 0) {includesList = Arrays.asList(includsArray);//构造列表对象} else {return;}Method[] fromMethods = from.getClass().getDeclaredMethods();Method[] toMethods = to.getClass().getDeclaredMethods();Method fromMethod = null, toMethod = null;String fromMethodName = null, toMethodName = null;for (int i = 0; i < fromMethods.length; i++) {fromMethod = fromMethods[i];fromMethodName = fromMethod.getName();if (!fromMethodName.contains("get"))continue;//排除列表检测String str = fromMethodName.substring(3);if(!includesList.contains(str.substring(0,1).toLowerCase() + str.substring(1))) {continue;}toMethodName = "set" + fromMethodName.substring(3);toMethod = findMethodByName(toMethods, toMethodName);if (toMethod == null)continue;Object value = fromMethod.invoke(from, new Object[0]);if(value == null)continue;//集合类判空处理if(value instanceof Collection) {Collection newValue = (Collection)value;if(newValue.size() <= 0)continue;}toMethod.invoke(to, new Object[] {value});}}/** * 从方法数组中获取指定名称的方法 *  * @param methods * @param name * @return */public static Method findMethodByName(Method[] methods, String name) {for (int j = 0; j < methods.length; j++) {if (methods[j].getName().equals(name))return methods[j];}return null;}

2 利用apache commons-beanutils的开源实现。

BeanUtils.copyProperties(dst, src)。方法能够将源对象和目标对象中相同名称的属性值复制过去。注意的是参数前面的是目标对象，后面是源对象。使用该方法需要注意：不能将入口方法与源对象、目标对象之一放在同一源文件之内，否者将没有任何效果。

PropertyUtils.copyProperties(dst, src)。功能与BeanUtils.copyProperties类似，只是在同属性名称的类型参数之间可以执行转换操作。

3 利用Spring实现属性之间的复制。spring内部自有实现方法，如果我们需要在外面采用spring的托管复制，需要修改spring的源码，将spring中的org.springframework.beans.CachedIntrospectionResults类的forClass、getPropertyDescriptor、getBeanInfo改为可见的后重新打包。然后将Spring中关于复制的代码提取出来，最后修改成代码如下：

/** * 利用spring实现bean之间属性复制 * @param source * @param target */@SuppressWarnings("unchecked")public static void copyPropertiesBySpring(Object source, Object target) throws Exception {Class actualEditable = target.getClass();PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);for (int i = 0; i < targetPds.length; i++) {PropertyDescriptor targetPd = targetPds[i];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, new Object[0]);if(value == null)continue;//集合类判空处理if(value instanceof Collection) {//Collection newValue = (Collection)value;//if(newValue.size() <= 0)continue;}Method writeMethod = targetPd.getWriteMethod();if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {writeMethod.setAccessible(true);}writeMethod.invoke(target, new Object[] { value });} catch (Throwable ex) {}}}}}/** * 获取指定类指定名称的属性描述符 * @param clazz * @param propertyName * @return * @throws BeansException */@SuppressWarnings("unchecked")public static PropertyDescriptor getPropertyDescriptor(Class clazz,String propertyName) throws BeansException {CachedIntrospectionResults cr = CachedIntrospectionResults.forClass(clazz);return cr.getPropertyDescriptor(propertyName);}/** * 获取指定类得所有属性描述符 * @param clazz * @return * @throws BeansException */@SuppressWarnings("unchecked")public static PropertyDescriptor[] getPropertyDescriptors(Class clazz) throws BeansException {CachedIntrospectionResults cr = CachedIntrospectionResults.forClass(clazz);return cr.getBeanInfo().getPropertyDescriptors();}