Java 克隆方式

• Java克隆介绍
• 代码实现
• • CloneableBO
  • CommonBO
  • SerializableBO
  • SerializableUtil
  • MainTest
• 为什么推荐选择深克隆？

  在Java中存在两种克隆方式：

1. 深克隆：不仅克隆对象本身，还克隆对象包含的引用所指向的所有对象。（通过实现Serilable接口）
2. 浅克隆：仅克隆对象本身，不可隆对象中的引用指向的对象。（通过实现Cloneable接口）

package clone;


public class CloneableBO implements Cloneable {

    
    private int id;

    
    private String name;

    
    private CommonBO commonBO;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public CommonBO getCommonBO() {
        return commonBO;
    }

    public void setCommonBO(CommonBO commonBO) {
        this.commonBO = commonBO;
    }

    @Override
    public String toString() {
        return "CloneableBO{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", commonBO=" + commonBO +
                '}';
    }

    @Override
    public CloneableBO clone() {
        try {
            CloneableBO clone = (CloneableBO) super.clone();
            // TODO: copy mutable state here, so the clone can't change the internals of the original
            return clone;
        } catch (CloneNotSupportedException e) {
            throw new AssertionError();
        }
    }
}

package clone;

import java.io.Serializable;


public class CommonBO implements Serializable {

    
    private String context;

    public CommonBO(String context) {
        this.context = context;
    }

    public String getContext() {
        return context;
    }

    public void setContext(String context) {
        this.context = context;
    }

    @Override
    public String toString() {
        return "CommonBO{" +
                "context='" + context + ''' +
                '}';
    }
}

package clone;

import java.io.Serializable;


public class SerializableBO implements Serializable {

    
    private int id;

    
    private String name;

    
    private CommonBO commonBO;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public CommonBO getCommonBO() {
        return commonBO;
    }

    public void setCommonBO(CommonBO commonBO) {
        this.commonBO = commonBO;
    }

    @Override
    public String toString() {
        return "SerializableBO{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", commonBO=" + commonBO +
                '}';
    }
}

package clone;

import java.io.*;


public class SerializableUtil {

    public static  T clone(T obj) throws IOException, ClassNotFoundException {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);
        objectOutputStream.writeObject(obj);

        ByteArrayInputStream inputStream = new ByteArrayInputStream(outputStream.toByteArray());
        ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
        return (T) objectInputStream.readObject();
    }
}

package clone;

import java.io.IOException;


public class MainTest {

    public static void main(String[] args) throws IOException, ClassNotFoundException {
        CloneableBO cloneableBO = new CloneableBO();
        cloneableBO.setId(1);
        cloneableBO.setName("小赵");
        cloneableBO.setCommonBO(new CommonBO("我是内容1"));
        System.out.println("cloneable 复制前 初始内容:" + cloneableBO);

        CloneableBO cloneableBOCopy = cloneableBO.clone();
        cloneableBOCopy.getCommonBO().setContext("我是内容2");
        System.out.println("cloneable 复制后 初始内容:" + cloneableBO);
        System.out.println("cloneable 复制后 复制内容:" + cloneableBOCopy);

        SerializableBO serializableBO = new SerializableBO();
        serializableBO.setId(2);
        serializableBO.setName("小李");
        serializableBO.setCommonBO(new CommonBO("我是内容3"));

        System.out.println("serializable 复制前 初始内容:" + serializableBO);
        SerializableBO serializableBOCopy = SerializableUtil.clone(serializableBO);
        serializableBOCopy.getCommonBO().setContext("我是内容4");
        System.out.println("serializable 复制后 初始内容:" + serializableBO);
        System.out.println("serializable 复制后 复制内容:" + serializableBOCopy);
    }
}

执行结果

  基于序列化和反序列化实现的克隆不仅仅是深度克隆，更重要的是通过泛型限定，可以检查出要克隆的对象是否支持序列化。这项检查是编译器完成的，不是在运行时抛出异常，这种方案明显优于使用Object类的clone方法克隆对象。让问题在编译的时候暴露出来总好过把问题留到运行时。