原型模式

我们从数据库获取数据到DTO，从DTO传递给VO，这个时候需要将DTO层的数据全部copy到VO中，这种模式就是一种原型模式。 copy的方式是克隆。

案例

• spring中的 scope=’prototype’是一个原型模式，每次创建的时候都是一个新的对象，这个对象会取到原有对象的所有的值。

浅克隆

public class Teacher implements Cloneable {

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
    public Teacher(String name, Student student, Date date) {
        this.name = name;
        this.student = student;
        this.date = date;
    }
    private String name;
    private Student student;
    private Date date;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Student getStudent() {
        return student;
    }
    public void setStudent(Student student) {
        this.student = student;
    }
    public Date getDate() {
        return date;
    }
    public void setDate(Date date) {
        this.date = date;
    }
}


public static void main(String[] args) throws CloneNotSupportedException {

       Student student=new Student(1,"张三");
        Teacher teacher = new Teacher("老师",  student,new Date());

        Teacher cloneTeacher =(Teacher) teacher.clone();
        System.out.println(teacher.getStudent().getClass() == cloneTeacher.getStudent().getClass());
        System.out.println(teacher+"||||||"+cloneTeacher);


        System.out.println("克隆后，比较克隆对象改变引用");
        System.out.println(teacher.getStudent()+"||||||"+ cloneTeacher.getStudent());
//true
//com.gpxy.clone.Teacher@2503dbd3||||||com.gpxy.clone.Teacher@4b67cf4d
//克隆后，比较克隆对象改变引用
//com.gpxy.clone.Student@7ea987ac||||||com.gpxy.clone.Student@7ea987ac

    }
    

深克隆

将所有的值都克隆，完全是新的一份，实现的方式也比较多。如：序列化，反射等。

public class DeepTeacher implements Cloneable,Serializable{

    @Override
    public DeepTeacher clone()  {
        try {
            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
            objectOutputStream.writeObject(this);

            ByteArrayInputStream byteArrayInputStream=new ByteArrayInputStream(byteArrayOutputStream.toByteArray());
            ObjectInputStream objectInputStream=new ObjectInputStream(byteArrayInputStream);
            DeepTeacher o = (DeepTeacher)objectInputStream.readObject();
            return o;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
    public DeepTeacher(String name, DeepStudent student, Date date) {
        this.name = name;
        this.student = student;
        this.date = date;
    }
    private String name;
    private DeepStudent student;
    private Date date;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public DeepStudent getStudent() {
        return student;
    }
    public void setStudent(DeepStudent student) {
        this.student = student;
    }
    public Date getDate() {
        return date;
    }
    public void setDate(Date date) {
        this.date = date;
    }
}

public class DeepStudent implements Cloneable, Serializable {

    private Integer id;
    private String name;
    public DeepStudent(Integer id, String name) {
        this.id = id;
        this.name = name;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

  public static void main(String[] args){
        DeepTeacher teacher=new DeepTeacher("teacher1", new DeepStudent(2, "学生"),new Date());
        DeepTeacher cloneDeepTeacher = teacher.clone();
        System.out.println(teacher+"----"+cloneDeepTeacher);
        System.out.println(teacher.getStudent()+"---"+cloneDeepTeacher.getStudent());
        System.out.println(teacher==cloneDeepTeacher);
    }
// 测试数据
//com.gpxy.clone.DeepTeacher@610455d6----com.gpxy.clone.DeepTeacher@27973e9b
//com.gpxy.clone.DeepStudent@63947c6b---com.gpxy.clone.DeepStudent@312b1dae
//false

由此可以看出deepStudet的地址变了。所以深度克隆是完全一个新的。