设计模式三 原型模式

0、 基本定义

定义：用原型实例指定创建的种类，并且通过拷贝这些原型创建新的对象。

implement Cloneable

不支持 final

BeanUtils copy 有使用反射实现

浅拷贝：字段是值类型，逐位复制；字段是引用类型，复制引用但不复制引用对象。

深拷贝：复制引用对象, 可通过 序列化方式实现。

1、代码参考

Resume.java

public class Resume implements Cloneable, Serializable{

    private String name;
    private String sex;
    private String age;
    private String timeArea;
    private String company;

    private WorkExperience work;

    public Resume(String name) {
        this.name = name;
        work = new WorkExperience();
    }

    public void setPersonalInfo(String sex, String age) {
        this.sex = sex;
        this.age = age;
    }

    public void setWorkExperience(String timeArea, String company) {
        this.timeArea = timeArea;
        this.company = company;

        //深 拷贝
        work.setCompany(company);
        work.setWorkDate(timeArea);
    }

    public void display() {
        System.out.println(String.join(" ", name, sex, age));
        System.out.println("工作经历：" + String.join(" ", timeArea, company                                                                                                 ));
        System.out.println("workExperience：" + String.join(" ", work.getCompany(), work.getWorkDate()                                                                                                 ));
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

//深拷贝 1
    public Object deepClone() throws IOException, ClassNotFoundException {
        // 序列化

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(bos);
        oos.writeObject(this);

        ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bis);
        Resume o = (Resume) ois.readObject();
        return o;
    }


　　//深拷贝 2 - 常规
    public Object deepClone2() throws Exception {

        Resume clone = (Resume) super.clone();
        clone.work = (WorkExperience) this.work.clone();
        return clone;
    }

    public String getName() {
        return name;
    }

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

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    public String getTimeArea() {
        return timeArea;
    }

    public void setTimeArea(String timeArea) {
        this.timeArea = timeArea;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }
}

 WorkExperience.java

public class WorkExperience implements Serializable,Cloneable{

    private String workDate;
    private String company;


    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

    public String getWorkDate() {
        return workDate;
    }

    public void setWorkDate(String workDate) {
        this.workDate = workDate;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }
}

Test.java

public class ResumeTest {

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

        //浅复制
        Resume resume = new Resume("fred");
        resume.setPersonalInfo("male", "29");
        resume.setWorkExperience("1990-2008", "company A");

//        Resume b = (Resume) resume.deepClone();
        Resume b = (Resume) resume.deepClone2();
//        Resume b = (Resume) resume.clone();

        System.out.println("resume == b？" + (resume == b));
        System.out.println("resume.getClass() == b.getClass()？" + (resume.getClass() == b.getClass()));
        b.setWorkExperience("2000-2015"," tongdun");

        Resume c = (Resume) resume.clone();
        c.setPersonalInfo("male", "30");

        System.out.println("===============");
        resume.display();
        System.out.println("===============");
        b.display();
        System.out.println("===============");
        c.display();

        System.out.println("=====deep clone ====");

    }
}

结果：

===============
fred male 29
工作经历：1990-2008 company A
workExperience： tongdun 2000-2015
===============
fred male 29
工作经历：2000-2015 tongdun
workExperience： tongdun 2000-2015
===============
fred male 30
工作经历：1990-2008 company A
workExperience： tongdun 2000-2015

======deep clone=========
fred male 29
工作经历：1990-2008 company A
workExperience：company A 1990-2008
===============
fred male 29
工作经历：2000-2015  tongdun
workExperience： tongdun 2000-2015   //使用深拷贝后
===============
fred male 30
工作经历：1990-2008 company A
workExperience：company A 1990-2008
=====deep clone ====

2 后续 

2.1 优点：

》原型模式是在内存 二进制流的拷贝，比new 性能要好

》逃避构造函数的约束

双刃剑

2.2 使用场景

 》资源优化场景

- 类初始化需要消耗很多的资源

》性能和安全要求的场景

- 通过new长生一个对象需要非常 繁琐的数据准备或访问权限

》一个对象多个修改者的场景

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 persistence 2.  这块语言描述总结不是很好，源于自己也还有些模糊， 待续完善。。。。。

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参考资料：

咕泡学院- 这块讲的一般

《大话设计模式》

《设计模式之蝉》