java深拷贝与c#深拷贝的实现

Posted 酒香逢

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了java深拷贝与c#深拷贝的实现相关的知识,希望对你有一定的参考价值。

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)

先说java的深拷贝方式0.0

java深拷贝方式一: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

 1 /**轮胎类**/
 2 public class Tire implements Cloneable {
 3     public String color;
 4     public int radius;
 5     public Tire(){}
 6     public Tire(String color, int radius) {
 7         this.color = color;
 8         this.radius = radius;
 9     }
10 
11     @Override
12     protected Object clone() throws CloneNotSupportedException {
13         return super.clone();
14     }
15 }
16 /**车辆类**/
17 public class Car implements Cloneable{
18     public String name;
19     public String color;
20     public Tire tire;
21     public Car() {}
22     public Car(String name, String color, Tire tire) {
23         this.name = name;
24         this.color = color;
25         this.tire = tire;
26     }
27     public void whistle(){
28         System.out.println("汽车"+this.name+" 鸣笛...");
29     }
30     public String getName() {
31         return name;
32     }
33     public void setName(String name) {
34         this.name = name;
35     }
36     public String getColor() {
37         return color;
38     }
39     public void setColor(String color) {
40         this.color = color;
41     }
42     public Tire getTire() {
43         return tire;
44     }
45     public void setTire(Tire tire) {
46         this.tire = tire;
47     }
48     @Override
49     protected Object clone() throws CloneNotSupportedException {
50         return super.clone();
51     }
52 }

 

单元测试:

 1 @Test
 2     public void test() throws CloneNotSupportedException {
 3         Tire tire = new Tire("black",100);
 4         Car car  = new Car("奔驰","white",tire);
 5         Car car_copy = (Car)car.clone();
 6         System.out.println("car:"+car.hashCode()+" car.tire:"+car.tire.hashCode());
 7         System.out.println("car_copy:"+car_copy.hashCode()+" car_copy.tire:"+car_copy.tire.hashCode());
 8         car_copy.color = "blue";
 9         System.out.println("car_copy:"+car_copy.color+"  car:"+car.color);
10     }

 

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:

1 @Override
2     protected Object clone() throws CloneNotSupportedException {
3         Car car = (Car)super.clone();
4         car.tire = (Tire)car.tire.clone();
5         return car;
6     }

 

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......

java深拷贝方式二: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:

 1 @SuppressWarnings("unchecked")
 2     public static Object deepClone(Object obj)
 3     {
 4         Object copyObj = null;
 5         ObjectOutputStream out = null;
 6         ObjectInputStream in = null;
 7         try {
 8             // 序列化
 9             ByteArrayOutputStream bufferOut = new ByteArrayOutputStream();
10             out = new ObjectOutputStream(bufferOut);
11 
12             out.writeObject(obj);
13 
14             // 反序列化
15             ByteArrayInputStream bufferIn = new ByteArrayInputStream(bufferOut.toByteArray());
16             in = new ObjectInputStream(bufferIn);
17             copyObj = in.readObject();
18         } catch (Exception e) {
19             e.printStackTrace();
20             throw new RuntimeException(e); 
21         }finally{
22              try{
23                  if(in != null){
24                      in.close();
25                  }
26                  if(out!=null){
27                      out.close();
28                  }
29              }catch(IOException e){
30                  throw new RuntimeException(e);
31              }
32         }
33         return copyObj;
34     }

 

单元测试:

 1 @Test
 2     public void test() throws CloneNotSupportedException {
 3         Tire tire = new Tire("black",100);
 4         Car car  = new Car("奔驰","white",tire);
 5         Car car_copy = (Car)deepClone(car);
 6         System.out.println("car:"+car.hashCode()+" car.tire:"+car.tire.hashCode());
 7         System.out.println("car_copy:"+car_copy.hashCode()+" car_copy.tire:"+car_copy.tire.hashCode());
 8         car_copy.color = "blue";
 9         System.out.println("car_copy:"+car_copy.color+"  car:"+car.color);
10     }

 

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...)

 1 @SuppressWarnings("unchecked")
 2     public static <T> T deepClone(T obj)
 3     {
 4         T copyObj = null;
 5         ObjectOutputStream out = null;
 6         ObjectInputStream in = null;
 7         try {
 8             // 序列化
 9             ByteArrayOutputStream bufferOut = new ByteArrayOutputStream();
10             out = new ObjectOutputStream(bufferOut);
11 
12             out.writeObject(obj);
13 
14             // 反序列化
15             ByteArrayInputStream bufferIn = new ByteArrayInputStream(bufferOut.toByteArray());
16             in = new ObjectInputStream(bufferIn);
17             copyObj = (T)in.readObject();
18         } catch (Exception e) {
19             e.printStackTrace();
20             throw new RuntimeException(e); 
21         }finally{
22              try{
23                  if(in != null){
24                      in.close();
25                  }
26                  if(out!=null){
27                      out.close();
28                  }
29              }catch(IOException e){
30                  throw new RuntimeException(e);
31              }
32         }
33         return copyObj;
34     }

 

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...

1 public Object deepClone(Object obj){
2         return org.apache.commons.lang.SerializationUtils.clone((Serializable)obj);
3     }

 

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

 1 /// <summary>
 2         /// 对象拷贝
 3         /// </summary>
 4         /// <param name="obj">被复制对象</param>
 5         /// <returns>新对象</returns>
 6         private object CopyOjbect(object obj) {
 7             if (obj == null) {
 8                 return null;
 9             }
10             Object targetDeepCopyObj;
11             Type targetType = obj.GetType();
12             //值类型  
13             if (targetType.IsValueType == true) {
14                 targetDeepCopyObj = obj;
15             }
16             //引用类型   
17             else {
18                 targetDeepCopyObj = System.Activator.CreateInstance(targetType);   //创建引用对象   
19                 System.Reflection.MemberInfo[] memberCollection = obj.GetType().GetMembers();
20 
21                 foreach (System.Reflection.MemberInfo member in memberCollection) {
22                     //拷贝字段
23                     if (member.MemberType == System.Reflection.MemberTypes.Field)
24                     {
25                         System.Reflection.FieldInfo field = (System.Reflection.FieldInfo)member;
26                         Object fieldValue = field.GetValue(obj);
27                         if (fieldValue is ICloneable)
28                         {
29                             field.SetValue(targetDeepCopyObj, (fieldValue as ICloneable).Clone());
30                         }
31                         else
32                         {
33                             field.SetValue(targetDeepCopyObj, CopyOjbect(fieldValue));
34                         }
35 
36                     }//拷贝属性
37                     else if (member.MemberType == System.Reflection.MemberTypes.Property) {
38                         System.Reflection.PropertyInfo myProperty = (System.Reflection.PropertyInfo)member;
39 
40                         MethodInfo info = myProperty.GetSetMethod(false);
41                         if (info != null) {
42                             try {
43                                 object propertyValue = myProperty.GetValue(obj, null);
44                                 if (propertyValue is ICloneable) {
45                                     myProperty.SetValue(targetDeepCopyObj, (propertyValue as ICloneable).Clone(), null);
46                                 }
47                                 else {
48                                     myProperty.SetValue(targetDeepCopyObj, CopyOjbect(propertyValue), null);
49                                 }
50                             }
51                             catch (System.Exception ex) {
52 
53                             }
54                         }
55                     }
56                 }
57             }
58             return targetDeepCopyObj;
59         }

 

以上是关于java深拷贝与c#深拷贝的实现的主要内容,如果未能解决你的问题,请参考以下文章

JavaScript深拷贝和浅拷贝数组

c#中大家是怎么做深拷贝的?一定要自己手动写代码吗?

C#的浅拷贝和深拷贝

Java 深拷贝浅拷贝 与 序列化

转载:浅析C#深拷贝与浅拷贝

深拷贝与浅拷贝的实现(一)