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
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/**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(); }} |
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@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：
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car:1223737555 car.tire:906199566car_copy:542081238 car_copy.tire:906199566car_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：
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@Override protected Object clone() throws CloneNotSupportedException { Car car = (Car)super.clone(); car.tire = (Tire)car.tire.clone(); return car; } |
输出结果：
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car:1223737555 car.tire:906199566car_copy:542081238 car_copy.tire:1133736492car_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
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/**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：
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@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：
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@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：
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car:2019524978 car.tire:855703640car_copy:1407965019 car_copy.tire:545768040car_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...）
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@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...
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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...
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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
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/// <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; } |
以上这篇一种c#深拷贝方式完胜java深拷贝(实现上的对比分析)就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持服务器之家。
