Map，List，POJO深拷贝(序列化实现)方法与注意事项

转载请注明出处，谢谢！

方法1：

 　　/*jdk >= 1.5*/
     @SuppressWarnings("unchecked")
     public static <T> T deepClone(T obj) {
         T clonedObj = null;
         ObjectOutputStream oos = null;
         ObjectInputStream ois = null;
         try {
             ByteArrayOutputStream baos = new ByteArrayOutputStream();
             oos = new ObjectOutputStream(baos);
             oos.writeObject(obj);
             ByteArrayInputStream bais = new ByteArrayInputStream(
                     baos.toByteArray());
             ois = new ObjectInputStream(bais);
             clonedObj = (T) ois.readObject();
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             try {
                 oos.close();
                 ois.close();
             } catch (IOException e) {
                 e.printStackTrace();
             }

         }
         return clonedObj;
     }

方法2：

 　　 /*jdk >= 1.7*/
     @SuppressWarnings("unchecked")
     public static <T> T deepCopy(T srcObj) {
         T targetObj = null;
         try
         (
             ByteArrayInputStream bais = new ByteArrayInputStream(deepCopyRepo(srcObj, new ByteArrayOutputStream()).toByteArray());
             ObjectInputStream ois = new ObjectInputStream(bais)
         )
         {
             targetObj = (T) ois.readObject();
         }
         catch (Exception e)
         {
             e.printStackTrace();
         }
         return targetObj;
     }
     public static ByteArrayOutputStream deepCopyRepo(Object obj,ByteArrayOutputStream baos) throws Exception {
         try
         (
             ObjectOutputStream oos = new ObjectOutputStream(baos)
         )
         {
             oos.writeObject(obj);
         }
         return baos;
     }

---

注意事项：

1.若Java 7 build 105 版本及以上,推荐使用方法2；try-with-resources语句，ARM(Automatic Resource Management) 自动资源管理。

2.被拷贝对象必须为可序列化的；当然，常用的如HashMap，ArrayList都是实现序列化的，直接使用本方法即可。

public class HashMap<K,V> extends AbstractMap<K,V> implements Map<K,V>, Cloneable, Serializable

public class ArrayList<E> extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, java.io.Serializable

---

示例POJO：

 import java.io.Serializable;
 import java.util.List;

 public class Person implements Serializable{
     /*自定义版本*/
     private static final long serialVersionUID = 1L;

     private String name;
     private List<Person> children;
     /*age属性因transient修饰，所以被序列化机制隔离*/
     private transient int age;
     public Person(String name,List<Person> children,int age){
         this.name = name;
         this.children = children;
         this.age = age;
     }
     public Person(){}
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public List<Person> getChildren() {
         return children;
     }
     public void setChildren(List<Person> children) {
         this.children = children;
     }
     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }
     @Override/*根据jvm返回的hashCode判断对象相同*/
     public String toString() {
         return "Person"+ "@" + Integer.toHexString(this.hashCode())+" [name=" + name + ", children=" + children + ", age="
                 + age + "]";
     }
 }

junit：

 　　@Test
     public void testDeepCopy(){
         List<Person> children = new ArrayList<>();
         Person daughter = new Person("daughter",null,3);
         Person son = new Person("son",null,1);
         children.add(son);children.add(daughter);
         Person father = new Person("sqiang",children,29);
         System.out.println(father);
         Person cfather = Utils.deepCopy(father);
         System.out.println(cfather);
     }

---

Console：

如图所示：

1.两组对象均不相同，实现了深拷贝

2.第二组的age=0，transient关键字对序列化起了作用。