楼主是一名asp.net攻城狮，最近经常跑java组客串帮忙开发，所以最近对java的一些基础知识特别上心。却遇到需要将一个对象深拷贝出来做其他事情，而原对象保持原有状态的情况。（实在是不想自己new一个出来，然后对着一堆字段赋值......好吧，再此之前我没有关心是否项目框架有深拷贝的方法），然后就想着用反射实现吧....接下来
是我自己的原因，还是真的不存在这样的纯用反射实现的深拷贝方式....（c#是有纯反射实现的）
但也不能算自己白忙活吧，也找到了其他实现深拷贝的方式（但是每种方式我都觉得并不是太合理，也许是因为c#的方式带入了吧，最后贴出c#版本纯反射实现深拷贝的代码）
方式一：实现Cloneable接口，重写clone方法
实体类：一个轮胎类，一个车辆类，车辆中包含轮胎
/**轮胎类**/
public class Tire implements Cloneable {
public String color;
public int radius;
public Tire(){}
public Tire(String color, int radius) {
this .color = color;
this .radius = radius;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
/**车辆类**/
public class Car implements Cloneable{
public String name;
public String color;
public Tire tire;
public Car() {}
public Car(String name, String color, Tire tire) {
this .name = name;
this .color = color;
this .tire = tire;
}
public void whistle(){
System. out .println( "汽车" + this .name+ " 鸣笛..." );
}
public String getName() {
return name;
}
public void setName(String name) {
this .name = name;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this .color = color;
}
public Tire getTire() {
return tire;
}
public void setTire(Tire tire) {
this .tire = tire;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
@Test
public void test() throws CloneNotSupportedException {
Tire tire = new Tire( "black" ,100);
Car car = new Car( "奔驰" , "white" ,tire);
Car car_copy = (Car)car.clone();
System. out .println( "car:" +car.hashCode()+ " car.tire:" +car.tire.hashCode());
System. out .println( "car_copy:" +car_copy.hashCode()+ " car_copy.tire:" +car_copy.tire.hashCode());
car_copy.color = "blue" ;
System. out .println( "car_copy:" +car_copy.color+ " car:" +car.color);
}
输出结果：
car:1223737555 car.tire:906199566
car_copy:542081238 car_copy.tire:906199566
car_copy:blue car:white
从结果可以的之，car与car_copy的内存地址并不一致，但car.tire与car_copy.tire的内存地址却是一致的，说明[奔驰]车确实又造出了一辆，但却公用同一幅轮胎（这种情形....哈哈哈），好吧，也就是只复制了tire的引用，这可以说是深拷贝的不彻底 （hashCode()的值可以当作是内存地址来理解），那么要怎样才能彻底，真正的深拷贝？
修改Car类中的clone方法：
@Override
protected Object clone() throws CloneNotSupportedException {
Car car = (Car)super.clone();
car.tire = (Tire)car.tire.clone();
return car;
}
输出结果：
car:1223737555 car.tire:906199566
car_copy:542081238 car_copy.tire:1133736492
car_copy:blue car:white
这样最终实现了，但这种方式用到项目中并不是很合适吧，每个需要深拷贝的类，都要实现Cloneable接口，并覆盖其clone方法，遇到引用其他类时候更是需要修改clone方法，要是引用其他类，其他类再引用其他类呢？这不好吧......
方式二：通过序列化与反序列化实现(实现Serializable接口)
实体类：与第一种方式类似，换成实现Serializable接口，去掉clone方法
/**轮胎类**/
@SuppressWarnings( "serial" )
public class Tire implements java.io.Serializable {
public String color;
public int radius;
public Tire(){}
public Tire(String color, int radius) {
this .color = color;
this .radius = radius;
}
}
/**车辆类**/
@SuppressWarnings( "serial" )
public class Car implements java.io.Serializable{
public String name;
public String color;
public Tire tire;
public Car() {}
public Car(String name, String color, Tire tire) {
this .name = name;
this .color = color;
this .tire = tire;
}
public void whistle(){
System.out.println( "汽车" + this .name+ " 鸣笛..." );
}
public String getName() {
return name;
}
public void setName(String name) {
this .name = name;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this .color = color;
}
public Tire getTire() {
return tire;
}
public void setTire(Tire tire) {
this .tire = tire;
}
}
深拷贝方法：
@SuppressWarnings( "unchecked" )
public static Object deepClone(Object obj)
{
Object copyObj = null ;
ObjectOutputStream out = null ;
ObjectInputStream in = null ;
try {
// 序列化
ByteArrayOutputStream bufferOut = new ByteArrayOutputStream();
out = new ObjectOutputStream(bufferOut);
out .writeObject(obj);
// 反序列化
ByteArrayInputStream bufferIn = new ByteArrayInputStream(bufferOut.toByteArray());
in = new ObjectInputStream(bufferIn);
copyObj = in .readObject();
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException(e);
} finally {
try {
if ( in != null ){
in .close();
}
if ( out != null ){
out .close();
}
} catch (IOException e){
throw new RuntimeException(e);
}
}
return copyObj;
}
单元测试：
@Test
public void test() throws CloneNotSupportedException {
Tire tire = new Tire( "black" ,100);
Car car = new Car( "奔驰" , "white" ,tire);
Car car_copy = (Car)deepClone(car);
System. out .println( "car:" +car.hashCode()+ " car.tire:" +car.tire.hashCode());
System. out .println( "car_copy:" +car_copy.hashCode()+ " car_copy.tire:" +car_copy.tire.hashCode());
car_copy.color = "blue" ;
System. out .println( "car_copy:" +car_copy.color+ " car:" +car.color);
}
输出结果：
car:2019524978 car.tire:855703640
car_copy:1407965019 car_copy.tire:545768040
car_copy:blue car:white
从结果集中可以看出是深拷贝是正确的，但是每个类还是需要实现Serializable，好像也不合适吧......
优化一下深拷贝方法：将其换成泛型，这样拷贝出来就不需要强转了（好吧，其实也没比上面的方法好到哪去...）
@SuppressWarnings( "unchecked" )
public static <T> T deepClone(T obj)
{
T copyObj = null ;
ObjectOutputStream out = null ;
ObjectInputStream in = null ;
try {
// 序列化
ByteArrayOutputStream bufferOut = new ByteArrayOutputStream();
out = new ObjectOutputStream(bufferOut);
out .writeObject(obj);
// 反序列化
ByteArrayInputStream bufferIn = new ByteArrayInputStream(bufferOut.toByteArray());
in = new ObjectInputStream(bufferIn);
copyObj = (T) in .readObject();
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException(e);
} finally {
try {
if ( in != null ){
in .close();
}
if ( out != null ){
out .close();
}
} catch (IOException e){
throw new RuntimeException(e);
}
}
return copyObj;
}
通过序列化与反序列化深拷贝还有更简单的实现方式，就是需要导个包（拷贝的类也必须实现Serializable接口），当然，我已经为你们准备好了 点击->org.apache.commons.lang
深拷贝方法：就一行代码...
public Object deepClone(Object obj){
return org.apache.commons.lang.SerializationUtils.clone((Serializable)obj);
}
好了，java的暂时就到这里了，当然对于这两种方式并不是很满意...
-------------------------------------------------
C#深拷贝 反射实现
下面方法是c#的深拷贝，纯反射实现，无需实现任何接口，哦对，需要实体类有个无参的构造方法，简单使用强大，微软大法好啊......有需要用到的同学就拿去用吧，目前经过一个几百W的项目框架中考验，真的强大实用
/// <summary>
/// 对象拷贝
/// </summary>
/// <param name="obj">被复制对象</param>
/// <returns>新对象</returns>
private object CopyOjbect( object obj) {
if (obj == null ) {
return null ;
}
Object targetDeepCopyObj;
Type targetType = obj.GetType();
//值类型
if (targetType.IsValueType == true ) {
targetDeepCopyObj = obj;
}
//引用类型
else {
targetDeepCopyObj = System.Activator.CreateInstance(targetType); //创建引用对象
System.Reflection.MemberInfo[] memberCollection = obj.GetType().GetMembers();
foreach (System.Reflection.MemberInfo member in memberCollection) {
//拷贝字段
if (member.MemberType == System.Reflection.MemberTypes.Field)
{
System.Reflection.FieldInfo field = (System.Reflection.FieldInfo)member;
Object fieldValue = field.GetValue(obj);
if (fieldValue is ICloneable)
{
field.SetValue(targetDeepCopyObj, (fieldValue as ICloneable).Clone());
}
else
{
field.SetValue(targetDeepCopyObj, CopyOjbect(fieldValue));
}
} //拷贝属性
else if (member.MemberType == System.Reflection.MemberTypes.Property) {
System.Reflection.PropertyInfo myProperty = (System.Reflection.PropertyInfo)member;
MethodInfo info = myProperty.GetSetMethod( false );
if (info != null ) {
try {
object propertyValue = myProperty.GetValue(obj, null );
if (propertyValue is ICloneable) {
myProperty.SetValue(targetDeepCopyObj, (propertyValue as ICloneable).Clone(), null );
}
else {
myProperty.SetValue(targetDeepCopyObj, CopyOjbect(propertyValue), null );
}
}
catch (System.Exception ex) {
}
}
}
}
}
return targetDeepCopyObj;
}
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