先给出一个情景：设计一个简历类

我们需要考虑的

  • 易于修改
  • 尽量减少实例化的次数（提高性能）

原型模式UML图

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原型模式：用原型实例指定创建对象的种类，并通过拷贝这些原型创建新的对象

基于模式原型的代码实现

原型类

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public abstract class Prototype implements Cloneable{
    private String id;
    public Prototype(String id) {
        this.id = id;
    }

    public String getId() { return id; }
    public void setId(String id) { this.id = id; }
}

具体原型类

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public class ConcretePrototype extends Prototype {
    public ConcretePrototype(String id) {
        super(id);
    }

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

客户端

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public static void main(String[] args) {
    ConcretePrototype p1 = new ConcretePrototype("I");
    ConcretePrototype c1 = null;
    try {
        c1 = (ConcretePrototype)p1.clone();
    } catch (Exception e) {
        e.printStackTrace();
    }
    System.out.println(c1.getId());
}

基于情景的代码实现

简历类

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public class Resume implements Cloneable {
    String name;
    String sex;
    public Resume(String name, String sex) {
        this.name = name;
        this.sex = sex;
    }

    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; }

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

客户端

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public static void main(String[] args) {
    Resume resume = new Resume("xyy", "girl");
    Resume resume1 = null;
    Resume resume2 = null;
    try {
        resume1 = (Resume) resume.clone();
        resume2 = (Resume) resume.clone();
    } catch (Exception e) {
        e.printStackTrace();
    }
    System.out.println(resume2.getName());
}

如果有引用类型的属性呢？

工作经历类
希望工作经历类对外不可见，所以没有提供含参构造方法。

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public class WorkExperience implements Cloneable {
    private String date;
    private String company;

    public String getDate() { return date; }
    public void setDate(String date) { this.date = date; }

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

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

简历类

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public class Resume2 implements Cloneable {
    private String name;
    private String sex;
    private WorkExperience workExperience;

    public Resume2(String name, String sex) {
        this.name = name;
        this.sex = sex;
    }
    private Resume2(WorkExperience workExperience) {
        try {
            this.workExperience = (WorkExperience)workExperience.clone();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    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 WorkExperience getWorkExperience() { return workExperience; }
    public void setWorkExperience(String date, String company) {
        if (this.workExperience != null) {
            this.getWorkExperience().setDate(date);
            this.getWorkExperience().setCompany(company);
        } else {
            WorkExperience workExperience = new WorkExperience();
            workExperience.setDate(date);
            workExperience.setCompany(company);
            this.workExperience = workExperience;
        }

    }

    @Override
    public Object clone() throws CloneNotSupportedException {
        Resume2 obj = new Resume2(this.workExperience);
        obj.name = this.name;
        obj.sex = this.sex;
        return obj;
    }
}

客户端

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public static void main(String[] args) {
    Resume2 resume = new Resume2("xyy", "girl");
    System.out.println(resume);
    resume.setWorkExperience("2020", "zjut");
    Resume2 resume1 = null;
    Resume2 resume2 = null;
    try {
        resume1 = (Resume2) resume.clone();
        resume2 = (Resume2) resume.clone();
    } catch (Exception e) {
        e.printStackTrace();
    }
    System.out.println(resume2.getName());
    System.out.println(resume2.getWorkExperience().getCompany());
}

本文部分内容改编于程杰老师的《大话设计模式》